Zhukov A.D. General reference foreman - file n1.rtf

One scientist figuratively said about seismic that “our entire civilization is built and develops on the lid of a cauldron, inside which terrible, unbridled tectonic elements boil, and no one is safe from not being on this jumping lid at least once in a lifetime.”

These "funny" words quite loosely interpret the problem. There is a rigorous science called seismology (“seismos” in Greek means “earthquake”, and this term was introduced about 120 years ago by the Irish engineer Robert Male), according to which the causes of earthquakes can be divided into three groups:

· Karst phenomena. This is the dissolution of carbonates contained in the soil, the formation of cavities that can collapse. Earthquakes caused by this phenomenon are usually of small magnitude.

· Volcanic activity. An example is the earthquake caused by the eruption of the volcano Krakatoa in the strait between the islands of Java and Sumatra in Indonesia in 1883. Ashes rose 80 km into the air, more than 18 km 3 fell, this caused bright dawns for several years. The eruption and a sea wave over 20 m high led to the death of tens of thousands of people on neighboring islands. Nevertheless, earthquakes caused by volcanic activity are observed relatively rarely.

· Tectonic processes. It is because of them that most earthquakes occur on the globe.

"Tektonikos" in translation from Greek - "build, builder, structure." Tectonics is the science of the structure of the earth's crust, an independent branch of geology.

There is a geological hypothesis of fixism, based on the concept of the inviolability (fixation) of the positions of the continents on the surface of the Earth and the decisive role of vertically directed tectonic movements in the development of the earth's crust.

Fixism is opposed to mobilism, a geological hypothesis first put forward by the German geophysicist Alfred Wegener in 1912 and suggesting large (up to several thousand km) horizontal displacements of large lithospheric plates. Observations from space allow us to speak about the unconditional correctness of this hypothesis.

The earth's crust is the outer shell of the earth. There are continental crust (from 35...45 km thick under the plains, up to 70 km in the mountains) and oceanic (5...10 km). In the structure of the first, there are three layers: the upper sedimentary, middle, conventionally called "granite", and the lower "basalt"; in the oceanic crust, the "granite" layer is absent, and the sedimentary layer has a reduced thickness. In the transition zone from the mainland to the ocean, an intermediate type of crust develops (subcontinental or suboceanic). Between the Earth's crust and the Earth's core (from the surface of Mohorovichich to a depth of 2900 km) is the Earth's mantle, which makes up 83% of the Earth's volume. It is assumed that it is mainly composed of olivine; due to the high pressure, the material of the mantle appears to be in a solid crystalline state, except in the asthenosphere, where it is possibly amorphous. The temperature of the mantle is 2000 ... 2500 o C. The lithosphere includes the earth's crust and the upper part of the mantle.

The boundary between the earth's crust and the Earth's mantle was identified by the Yugoslav seismologist A. Mohorovichich in 1909. The velocity of longitudinal seismic waves when passing through this surface increases abruptly from 6.7...7.6 to 7.9...8.2 km/s.

According to the theory of "plane tectonics" (or "plate tectonics") of the Canadian scientists Forte and Mitrovitz, the earth's crust throughout its entire thickness and even slightly below the surface of Mohorovic is divided by cracks into platform planes (tectonic lithospheric plates), which carry the load of oceans and continents . 11 large plates have been identified (African, Indian, North American, South American, Antarctic, Eurasian, Pacific, Caribbean, Cocos plate west of Mexico, Nazca plate west of South America, Arabian) and many smaller ones. Plates have a different location in height. The seams between them (the so-called seismic faults) are filled with much less durable material than the material of the plates. The plates seem to float in the earth's mantle and constantly collide with one another's edges. There is a schematic map showing the directions of movement of tectonic plates (relatively relative to the African plate).

According to N. Calder, there are three types of joints between plates:

A fissure formed when plates move away from each other (North American from Eurasian). This results in an annual increase in the distance between New York and London by 1 cm;

Trench - an oceanic depression along the boundary of the plates when they approach each other, when one of them bends and plunges under the edge of the other. This happened on December 26, 2004, west of the island of Sumatra, during the collision of the Indian and Eurasian plates;

Transform fault - sliding of plates relative to each other (Pacific relative to North American). Americans sadly joke that San Francisco and Los Angeles will sooner or later be connected, as they are located on different banks of the Saint Andreas seismic fault (San Francisco is on the North American plate, and the narrow California section, together with Los Angeles, is on Pacific) about 900 km long and moving towards each other at a speed of 5 cm/year. When an earthquake occurred here in 1906, 350 km out of the indicated 900 km shifted and froze with a shift of up to 7 m at once. There is a photograph that shows how one part of the fence of a Californian farmer shifted along the fault line relative to the other. According to the predictions of some seismologists, as a result of a catastrophic earthquake, the California peninsula may break away from the mainland along the Gulf of California and turn into an island or even go to the bottom of the ocean.

Most seismologists associate the occurrence of earthquakes with the sudden release of elastic deformation energy (the theory of elastic release). According to this theory, long and very slow deformations occur in the fault area - tectonic movement. It leads to the accumulation of stresses in the plate material. Stresses grow and grow and at a certain point in time reach the ultimate value for the strength of rocks. There is a rupture of rocks. The gap causes a sudden rapid displacement of the plates - a push, an elastic return, as a result of which seismic waves arise. Thus, prolonged and very slow tectonic movements turn into seismic movements during an earthquake. They have a high speed due to the rapid (within 10 ... 15 s) "discharge" of the accumulated huge energy. The maximum energy of an earthquake recorded on Earth is 10 18 J.

Tectonic movements occur at a considerable length of the plate junction. The rupture of rocks and the seismic movements caused by it occur at some local section of the junction. This site can be located at different depths from the Earth's surface. The indicated area is called the source or hypocentral region of the earthquake, and the point of this region, where the rupture began, is called the hypocenter or focus.

Sometimes not all the accumulated energy is “discharged” at once. The unreleased part of the energy causes stresses in new bonds, which after some time reach the ultimate value for rock strength in some areas, as a result of which an aftershock occurs - a new rupture and a new push, however, of lesser force than at the time of the main earthquake.

Earthquakes are preceded by weaker shocks - foreshocks. Their appearance is associated with the achievement in the massif of such stress levels at which local destruction occurs (in the weakest parts of the rock), but the main crack cannot yet form.

If the earthquake source is located at a depth of up to 70 km, then such an earthquake is called normal, at a depth of more than 300 km - deep focus. With an intermediate depth of focus and earthquakes are called intermediate. Deep-focus earthquakes are rare, they occur in the area of ​​oceanic depressions, they are distinguished by a large amount of released energy and, consequently, the greatest manifestation effect on the Earth's surface.

The effect of earthquake manifestation on the Earth's surface, and hence their destructive effect, depends not only on the amount of energy released during a sudden rupture of material in the source, but also on the hypocentral distance. It is defined as the hypotenuse of a right triangle whose legs are the epicentral distance (the distance from the point on the Earth's surface where the intensity of the earthquake is determined to the epicenter - the projection of the hypocenter onto the Earth's surface) and the depth of the hypocenter.

If we find points on the surface of the Earth around the epicenter where an earthquake manifests itself with the same intensity, and connect them with lines, we will get closed curves - isoseits. Near the epicenter, the shape of the isoseites to a certain extent repeats the shape of the focus. With distance from the epicenter, the intensity of the effect weakens, and the regularity of this weakening depends on the energy of the earthquake, the features of the source, and the environment in which seismic waves pass.

During earthquakes, the Earth's surface experiences vertical and horizontal vibrations. Vertical fluctuations are very significant in the epicentral zone, however, already at a relatively small distance from the epicenter, their value rapidly decreases, and here one has mainly to reckon with horizontal influences. Since cases of the location of the epicenter within or near settlements are rare, until recently only horizontal oscillations were taken into account in the design. As the building density increases, the danger of the location of epicenters within the boundaries of settlements increases accordingly, and therefore vertical oscillations also have to be taken into account.

Depending on the effect of the manifestation of an earthquake on the surface of the Earth, they are classified according to the intensity in points, which is determined by various scales. In total, about 50 such scales were proposed. Among the first are the Rossi-Forel (1883) and Mercalli-Cancani-Zyberg (1917) scales. The latter scale is still used in some European countries. Since 1931, the United States has been using a modified 12-point Mercalli scale (MM for short). The Japanese have their own 7-point scale.

Everyone knows the Richter scale. But it has nothing to do with classification by intensity in points. It was proposed in 1935 by the American seismologist C. Richter and theoretically substantiated jointly with B. Gutenberg. This is a scale of magnitudes, a conditional characteristic of the strain energy released by an earthquake source. The magnitude is found by the formula

where is the maximum displacement amplitude in a seismic wave, measured during the considered earthquake at some distance (km) from the epicenter, µm (10 -6 m);

The maximum displacement amplitude in a seismic wave, measured during some very weak (“zero” earthquake) at some distance (km) from the epicenter, µm (10 -6 m).

When used to determine displacement amplitudes superficial waves recorded by observation stations are received

This formula makes it possible to find the value of , measured by only one station, knowing . If, for example, 0.1 m \u003d 10 5 microns and 200 km, 2.3, then

The Ch. Richter scale (classification of earthquakes by magnitude) can be presented in the form of a table:

Thus, the magnitude only well characterizes the phenomenon that occurred in the earthquake source, but does not provide information about its destructive effect on the Earth's surface. This is the “prerogative” of other, already named scales. Therefore, the statement of the Chairman of the Council of Ministers of the USSR N.I. Ryzhkov after the Spitak earthquake that "the magnitude of the earthquake was 10 points on the Richter scale' is meaningless. Yes, the intensity of the earthquake, indeed, was equal to 10 points, but on the MSK-64 scale.

International scale of the Institute of Physics of the Earth. O.Yu. Schmidt of the Academy of Sciences of the USSR MSK-64 was created within the framework of the UES by S.V. Medvedev (USSR), Sponhoer (GDR) and Karnik (Czechoslovakia). It is named after the first letters of the names of the authors - MSK. The year of creation, as the name implies, is 1964. In 1981 the scale was modified and it became known as MSK-64*.

The scale contains instrumental and descriptive parts.

The instrumental part is decisive for assessing the intensity of earthquakes. It is based on the readings of a seismometer - a device that fixes the maximum relative displacements in a seismic wave using a spherical elastic pendulum. The period of natural oscillations of the pendulum is chosen so that it is approximately equal to the period of natural oscillations of low-rise buildings - 0.25 s.

Classification of earthquakes according to the instrumental part of the scale:

The table shows that the ground acceleration at 9 points is 480 cm / s 2, which is almost half = 9.81 m / s 2. Each score corresponds to a twofold increase in ground acceleration; at 10 points it would be equal already.

The descriptive part of the scale consists of three sections. In the first one, the intensity is classified according to the degree of damage to buildings and structures carried out without anti-seismic measures. The second section describes residual phenomena in soils, changes in the regime of groundwater and groundwater. The third section is called “other signs”, which includes, for example, the reaction of people to an earthquake.

Damage assessment is given for three types of buildings erected without anti-seismic reinforcements:

Classification of the degree of damage:

Degree of damage	Damage name	Damage characteristic
	Light damage	Small cracks in the walls, chipping of small pieces of plaster.
	Moderate Damage	Small cracks in the walls, small cracks in the joints between the panels, chipping of rather large pieces of plaster; falling tiles from roofs, cracks in chimneys, falling parts of chimneys (meaning building chimneys).
	Heavy Damage	Large deep and through cracks in the walls, significant cracks in the joints between panels, falling chimneys.
	destruction	Collapse of internal walls and walls filling the frame, gaps in the walls, collapse of parts of buildings, destruction of connections (communications) between individual parts of the building.
	collapses	Complete destruction of the building.

If there are anti-seismic reinforcements in the structures of buildings that correspond to the intensity of earthquakes, their damage should not exceed the 2nd degree.

Damage to buildings and structures erected without anti-seismic measures:

Scale, points	Characteristics of damage to different types of buildings
	1st degree in 50% of type A buildings; 1st degree in 5% of type B buildings; 2nd degree in 5% of type A buildings.
	1st degree in 50% of type B buildings; 2nd degree in 5% of type B buildings; 2nd degree in 50% of type B buildings; 3rd degree in 5% of type B buildings; 3rd degree in 50% of type A buildings; 4th degree in 5% of type A buildings. Cracks in stone fences.
	2nd degree in 50% of type B buildings; 3rd degree in 5% of type B buildings; 3rd degree in 50% of type B buildings; 4th degree in 5% of type B buildings; 4th degree in 50% of type A buildings; 5th degree in 5% of buildings of type A Monuments and statues are moved, tombstones are overturned. The stone walls are crumbling.
	3rd degree in 50% of type B buildings; 4th degree in 5% of type B buildings; 4th degree in 50% of type B buildings; 5th degree in 5% of type B buildings; 5th degree in 75% of type A buildings. Monuments and columns topple over.

Residual phenomena in soils, changes in the regime of groundwater and groundwater:

Scale, points	Characteristic features
1-4	There are no violations.
	Small waves in flowing waters.
	In some cases, landslides; visible cracks up to 1 cm wide are possible on damp soils; in mountainous areas - individual landslides, changes in the flow rate of sources and the level of water in wells are possible.
	In some cases, landslides of carriageways on steep slopes and cracks in the roads. Violation of the joints of pipelines. In some cases - changes in the flow rate of sources and water levels in wells. In few cases, existing water sources are created or lost. Individual cases of landslides on sandy and gravelly river banks.
	Small landslides on the steep slopes of cuts and embankments of roads, cracks in the soil reach several centimeters. Potential for new reservoirs to emerge. In many cases, the flow rate of springs and the water level in wells change. Sometimes dry wells fill up with water or existing ones dry up.
	Significant damage to the banks of artificial reservoirs, breaks in parts of underground pipelines. In some cases - the curvature of the rails and damage to the carriageways. On the flood plains, sand and silt deposits are often noticeable. Cracks in the soil up to 10 cm, and along the slopes and banks - more than 10 cm. In addition, there are many thin cracks in the soil. Frequent landslides and shedding of soil, rock falls.

Other signs:

Scale, points	Characteristic features
	People don't feel it.
	It is noted by some very sensitive people who are at rest.
	Noted by a few, very slight swinging of hanging objects.
	Slight swinging of hanging objects and stationary vehicles. Weak clatter of dishes. Recognized by all people inside buildings.
	Noticeable swinging of hanging objects, pendulum clocks stop. Unstable utensils tip over. Felt by all people, everyone wakes up. The animals are worried.
	Books fall from shelves, paintings move, light furniture. Dishes fall. Many people run out of the premises, the movement of people is unstable.
	All features 6 points. All people run out of the premises, sometimes jump out of the windows. It is difficult to move without support.
	Some of the hanging lamps are damaged. Furniture shifts and often topples. Light objects bounce and fall. People have difficulty keeping their feet. Everyone runs out of the premises.
	Furniture topples over and breaks. Great animal anxiety.

The correspondence between the Ch. Richter scale and MSK-64 * (the magnitude of the earthquake and its destructive consequences on the Earth's surface) can be displayed as a first approximation in the following form:

From 1 to 10 million plate collisions (earthquakes) occur annually, many of them are not even felt by a person, the consequences of others are comparable to the horrors of war. World seismicity statistics for the 20th century shows that the number of earthquakes with a magnitude of 7 and above ranged from 8 in 1902 and 1920 to 39 in 1950. The average number of earthquakes with a magnitude of 7 and above is 20 per year, with a magnitude of 8 and above - 2 per year.

The history of earthquakes indicates that geographically they are concentrated mainly along the so-called seismic belts, which practically coincide with faults and adjoin them.

75% of earthquakes occur in the Pacific seismic belt, covering almost the perimeter of the entire Pacific Ocean. Near our Far Eastern borders, it passes through the Japanese and Kuril Islands, Sakhalin Island, the Kamchatka Peninsula, the Aleutian Islands to the Gulf of Alaska and then extends along the entire western coast of North and South America, including British Columbia in Canada, the states of Washington, Oregon and California in the USA, Mexico, Guatemala, El Salvador, Nicaragua, Costa Rica, Panama, Colombia, Ecuador, Peru and Chile. Chile is an already inconvenient country, stretching in a narrow strip for 4300 km, so besides, it stretches along the fault between the Nazca plate and the South American plate; and the type of joint here is the most dangerous - the second.

23% of earthquakes occur in the Alpine-Himalayan (another name is the Mediterranean-Trans-Asian) seismic belt, which in particular includes the Caucasus and the nearest Anatolian fault. The Arabian plate, moving in a northeasterly direction, "rams" the Eurasian plate. Seismologists register a gradual migration of potential earthquake epicenters from Turkey towards the Caucasus.

There is a theory that the harbinger of earthquakes is an increase in the stress state of the earth's crust, which, shrinking like a sponge, pushes water out of itself. Hydrogeologists at the same time register an increase in the level of groundwater. Before the Spitak earthquake, the groundwater level in the Kuban and Adygea rose by 5-6 m and has remained virtually unchanged since then; the reason for this was attributed to the Krasnodar reservoir, but seismologists believe otherwise.

Only about 2% of earthquakes occur in the rest of the Earth.

The strongest earthquakes since 1900: Chile, May 22, 1960 - magnitude 9.5; Alaska Peninsula March 28, 1964 - 9.2; at the island. Sumatra, December 26, 2004 - 9.2, tsunami; Aleutian Islands, March 9, 1957 - 9.1; Kamchatka Peninsula, November 4, 1952 - 9.0. The top ten earthquakes also include earthquakes on the Kamchatka Peninsula on February 3, 1923 - 8.5 and on the Kuril Islands on October 13, 1963 - 8.5.

The maximum intensity expected for each area is called seismicity. There is a scheme of seismic zoning and a list of seismicity of settlements in Russia.

We live in the Krasnodar Territory.

In the 70s, most of it, according to the map of seismic zoning of the territory of the USSR according to SNiP II-A.12-69, did not belong to zones with high seismicity, only a narrow strip of the Black Sea coast from Tuapse to Adler was considered seismically hazardous.

In 1982, according to SNiP II-7-81, the zone of increased seismicity lengthened due to the inclusion of the cities of Gelendzhik, Novorossiysk, Anapa, part of the Taman Peninsula; it also expanded inland - to the city of Abinsk.

On May 23, 1995, Deputy Minister of the Ministry of Construction of the Russian Federation S.M. Poltavtsev, all the leaders of the republics, heads of administrations of territories and regions of the North Caucasus, research institutes, design and construction organizations were sent a List of settlements in the North Caucasus indicating the new seismicity adopted for them in points and the frequency of seismic impacts. This List was approved by the Russian Academy of Sciences on April 25, 1995 in accordance with the Temporary Scheme of Seismic Zoning of the North Caucasus (VSSR-93), compiled at the Institute of Physics of the Earth on behalf of the government after the catastrophic Spitak earthquake on December 7, 1988.

According to VSSR-93, now most of the territory of the Krasnodar Territory, with the exception of its northern regions, fell into a seismically active zone. For Krasnodar, the intensity of earthquakes began to be 8 3 (indices 1, 2 and 3 corresponded to the average frequency of earthquakes once in 100, 1000 and 10,000 years or the probability of 0.5; 0.05; 0.005 in the next 50 years).

Until now, there are different points of view on the expediency or inexpediency of such a drastic change in the assessment of potential seismic hazard in the region.

An interesting analysis of the maps shows the locations of the last 100 earthquakes in the territory of the region since 1991 (average 8 earthquakes per year) and the last 50 earthquakes since 1998 (also an average of 8 earthquakes per year). Most earthquakes still occurred in the Black Sea, but their "deepening" on land was also observed. The three strongest earthquakes were observed in the area of ​​the village of Lazarevsky, on the Krasnodar-Novorossiysk highway and on the border of the Krasnodar and Stavropol Territories.

In general, earthquakes in our region can be described as quite frequent, but not very strong. Their specific energy per unit area (in 10 10 J / km 2) is less than 0.1. For comparison: in Turkey -1 ... 2, in Transcaucasia - 0.1 ... 0.5, in Kamchatka and the Kuriles - 16, in Japan - 14 ... 15.9.

Since 1997, the intensity of seismic impacts in points for construction areas began to be taken on the basis of a set of maps of the general seismic zoning of the territory of the Russian Federation (OSR-97), approved by the Russian Academy of Sciences. The specified set of maps provides for the implementation of anti-seismic measures during the construction of facilities and reflects 10% - (map A), 5% - (map B) and 1% (map C) the probability of a possible excess (or, respectively, 90% -, 95% - and 99% probability of not exceeding) for 50 years the values ​​of seismic activity indicated on the maps. The same estimates reflect a 90% probability of not exceeding the intensity values ​​for 50 (map A), 100 (map B), and 500 (map C) years. The same estimates correspond to the frequency of such earthquakes on average once every 500 (map A), 1000 (map B), and 5000 (map C) years. According to OSR-97, for Krasnodar, the intensity of seismic impacts is 7, 8, 9.

The set of maps OSR-97 (A, B, C) allows assessing the degree of seismic hazard at three levels and provides for the implementation of anti-seismic measures during the construction of objects of three categories, taking into account the responsibility of structures:

map A - mass construction;

maps B and C - objects of increased responsibility and especially responsible objects.

Here is a selection from the list of settlements in the Krasnodar Territory located in seismic regions, indicating the estimated seismic intensity in points of the MSK-64 scale * :

Names of settlements	Maps OSR-97
A	IN	WITH
Abinsk
Abrau-Durso
Adler
Anapa
Armavir
Akhtyrsky
Belorechensk
Vityazevo
Vyselki
Gaiduk
Gelendzhik
Dagomys
Dzhubga
Divnomorskoe
Dinskaya
Yeysk
Ilsky
Kabardinka
Korenovsk
Krasnodar
Krinitsa
Kropotkin
Kurganinsk
Kushchevskaya
Labinsk
Ladoga
Lazarevskoe
Leningradskaya
Loo
Magri
Matsesta
Mezmay
Mostovskoy
Neftegorsk
Novorossiysk
Temryuk
Timashevsk
Tuapse
hosta

According to OSR-97, for the city of Krasnodar, the intensity of seismic impacts is 7, 8, 9. That is, there was a decrease in seismicity by 1 point compared to VSSR-93. It is interesting that the border between the 7- and 8-point zones, as a matter of fact, "caved" beyond the city of Krasnodar, beyond the river. Kuban. The border curved in the same way near the city of Sochi (8 points).

The seismic intensity indicated on the maps and in the list of settlements refers to areas with some average mining and geological conditions (category II of soils in terms of seismic properties). Under conditions other than average, the seismicity of a particular construction site is specified on the basis of microzoning data. In the same city, but in its different districts, seismicity can be significantly different. In the absence of seismic microzoning materials, a simplified determination of the seismicity of the site is allowed according to the table SNiP II-7-81 * (permafrost soils are omitted):

Soil category by seismic properties	soils	Seismicity of the construction site in case of seismicity of the area, points
I	Rocky soils of all types are not weathered and slightly weathered, coarse clastic soils are dense, low-moisture from igneous rocks, containing up to 30% of sandy-argillaceous filler.
II	Rocky soils are weathered and heavily weathered; coarse-grained soils, with the exception of those referred to category I; gravelly sands, large and medium-sized dense and medium-density low-moisture and moist, fine and silty sands dense and medium-density low-moisture, clayey soils with a consistency index at a porosity coefficient - for clays and loams and - for sandy loams.
III	Sands are loose, regardless of the degree of moisture and fineness; gravel sands, large and medium-sized, dense and medium-density water-saturated; fine and silty sands, dense and medium density, moist and water-saturated; clay soils with a consistency index at a porosity coefficient - for clays and loams and - for sandy loams.			> 9

The zone where an earthquake causes significant damage to buildings and structures is called meisoseismic or pleistoseismic. It is limited to a 6-point isoseist. With an intensity of 6 points and less damage to ordinary buildings and structures is small, and therefore, for such conditions, design is carried out without taking into account seismic hazard. The exception is some special productions, for which the design may take into account 6-magnitude, and sometimes less intense earthquakes.

The design of buildings and structures, taking into account the requirements of anti-seismic construction, is carried out for conditions of 7-, 8- and 9-point intensity.

As for 10-point and more intense earthquakes, for such cases, any seismic protection measures are insufficient.

Here are the statistics of material losses from earthquakes in buildings and structures designed and built without taking into account and taking into account anti-seismic measures:

Here are the statistics of damage to buildings of various types:

Percentage of buildings damaged by earthquakes

Earthquake prediction is a thankless task.

As a truly bloody example, the following story can be cited.

Chinese scientists in 1975 predicted the time of the earthquake in Liao-Lini (former Port Arthur). Indeed, the earthquake occurred at the predicted time, only 10 people died. In 1976, at an international conference, the report of the Chinese on this subject caused a sensation. And in the same 1976, the Chinese failed to predict the Tanshan (not the Tien Shan, as the journalists misrepresented, namely the Tanshan - from the name of the large industrial center Tanshan with a population of 1.6 million people) earthquake. The Chinese agreed with the number of 250 thousand victims, however, according to the average estimates, the death toll during this earthquake was 650 thousand, and according to pessimistic estimates, about 1 million people.

Predictions of earthquake intensity also often make God laugh.

In Spitak, according to the SNiP II-7-81 map, an earthquake with an intensity of more than 7 points should not have occurred, but a “shake” with an intensity of 9 ... 10 points. In Gazli, they also "wrong" by 2 points. The same "mistake" occurred in Neftegorsk on Sakhalin Island, which was completely destroyed.

How to curb this natural element, how to make buildings and structures located practically on vibration platforms, any of which is ready to “start up” at any moment, seismically resistant? These problems are solved by the science of earthquake-resistant construction, perhaps the most difficult for modern technical civilization; its complexity lies in the fact that we must "upfront" take action against an event whose destructive power cannot be predicted. Many earthquakes occurred, many buildings with a variety of structural schemes collapsed, but many buildings and structures were able to resist. The richest, mostly sad, literally bloody experience has been accumulated. And much of this experience was included in SNiP II-7-81 * "Construction in seismic regions."

Here are samples from SNiP, territorial SN of the Krasnodar Territory SNCK 22-301-99 "Construction in the seismic regions of the Krasnodar Territory", the currently discussed draft of new norms and other literary sources relating to buildings with load-bearing walls made of brick or masonry.

Masonry is an inhomogeneous body consisting of stone materials and joints filled with mortar. An introduction to the reinforcement masonry is obtained reinforced masonry structures. Reinforcement can be transverse (grids are located in horizontal joints), longitudinal (reinforcement is located outside under a layer of cement mortar or in grooves left in the masonry), reinforcement by including reinforced concrete in the masonry (complex structures) and reinforcement by enclosing the masonry in a reinforced concrete or metal cage from the corners.

As stone materials in conditions of high seismicity, artificial and natural materials are used in the form of bricks, stones, small and large blocks:

a) solid or hollow brick with 13, 19, 28 and 32 holes with a diameter of up to 14 mm of grade not lower than 75 (the grade characterizes the compressive strength); the size of a solid brick is 250x120x65 mm, hollow - 250x120x65 (88) mm;

b) with a design seismicity of 7 points, hollow ceramic stones with 7, 18, 21 and 28 holes of grade not lower than 75 are allowed; size of stones 250x120x138 mm;

c) concrete stones measuring 390x90(190)x188 mm, solid and hollow blocks made of concrete with a bulk density of at least 1200 kg/m 3 grade 50 and above;

d) stones or blocks from shell rocks, limestones of grade not less than 35, tuffs, sandstones and other natural materials of grade 50 and higher.

Stone masonry materials must meet the requirements of the relevant GOSTs.

It is not allowed to use stones and blocks with large voids and thin walls, masonry with backfill and others, the presence of large voids in which leads to stress concentration in the walls between the voids.

The construction of residential buildings made of mud brick, adobe and soil blocks in areas with high seismicity is prohibited. In rural areas with seismicity up to 8 points, the construction of one-story buildings from these materials is allowed, provided that the walls are reinforced with a wooden antiseptic frame with diagonal braces, while parapets made of raw and soil materials are not allowed.

masonry mortar usually used simple (on a binder of the same type). The brand of the solution characterizes its compressive strength. The solution must meet the requirements of GOST 28013-98 “Construction mortars. General technical conditions".

The strength limits of stone and mortar "dictate" the strength limit of the masonry as a whole. There is a formula prof. L.I. Onishchik to determine the tensile strength of all types of masonry under short-term loading. The limit of long-term (unlimited time) masonry resistance is about (0.7 ... 0.8).

Stone and reinforced masonry structures work well, mainly in compression: central, eccentric, oblique eccentric, local (collapse). They perceive bending, central stretching and shearing much worse. In SNiP II-21-81 "Stone and reinforced masonry structures" the corresponding methods for calculating structures for the limit states of the first and second groups are given.

These methods are not considered here. After getting acquainted with reinforced concrete structures, the student is able to independently master them (if necessary). This section of the course outlines only constructive anti-seismic measures that must be carried out during the construction of stone buildings in areas with high calculated seismicity.

So, first about stone materials.

Their adhesion to the mortar in the masonry is affected by:

• construction of stones (it has already been mentioned);

the condition of their surface (before laying, the stones must be thoroughly cleaned of deposits obtained during transportation and storage, as well as deposits associated with shortcomings in the stone production technology, from dust, ice; after a break in masonry work, the top row of masonry should also be cleaned);

the ability to absorb water (brick, stones from light rocks (< 1800 кг/м3), а также крупные блоки с целью уменьшения поглощения воды из раствора должны перед укладкой смачиваться. Однако степень увлажнения не должна быть чрезмерной, чтобы не получалось разжижение раствора, поскольку как обезвоживание, так и разжижение раствора снижают сцепление.

The construction laboratory must determine the optimal ratio between the pre-moistening of the stone and the water content of the mortar mixture.

Studies show that porous natural stones, as well as dry baked bricks from loess-like loams, with high water absorption (up to 12 ... 14%), must be immersed in water for at least 1 minute (they are moistened up to 4 ... 8 %). When supplying bricks to the workplace in containers, soaking can be done by lowering the container into water for 1.5 minutes and putting it into the "case" as quickly as possible, minimizing the time spent outdoors. After a break in masonry work, the top row of masonry should also be soaked.)

Now - about the solution.

Piece hand laying should be carried out on mixed cement mortars of grade not lower than 25 in summer conditions and not lower than 50 in winter. When erecting walls from vibrated brick or stone panels or blocks, mortars of a grade of at least 50 should be used.

To ensure good adhesion of stones to the mortar in the masonry, the latter must have high adhesion (gluing ability) and ensure the completeness of the area of ​​​​contact with the stone.

The following factors influence the amount of normal adhesion:

those that depend on stones, we have already listed (their design, surface condition, ability to absorb water);

and here are those that depend on the solution. This:

• its composition;
• tensile strength;
• mobility and water-holding capacity;
• hardening mode (humidity and temperature);
• age.

In purely cement-sand mortars, a large shrinkage occurs, accompanied by a partial separation of the mortar from the surface of the stone, and thereby reducing the effect of the high adhesive power of such mortars. As the content of lime (or clay) in cement-lime mortars increases, its water-retaining capacity increases and shrinkage deformations in the joints decrease, but at the same time the adhesive ability of the mortar deteriorates. Therefore, to ensure good adhesion, the construction laboratory must determine the optimal content of sand, cement and plasticizer (clay or lime) in the solution. As special additives that increase adhesion, various polymer compositions are recommended: divinylstyrene latex SKS-65GP(B) according to TU 38-103-41-76; copolymer vinyl chloride latex VKhVD-65 PC according to TU 6-01-2-467-76; polyvinyl acetate emulsion PVA according to GOST 18992-73.

Polymers are introduced into the solution in an amount of 15% by weight of cement in terms of the dry residue of the polymer.

With an estimated seismicity of 7 points, special additives may not be used.

To prepare a solution for earthquake-resistant masonry, sand with a high content of clay and dust particles cannot be used. Portland slag cement and pozzolanic Portland cement must not be used. When choosing cements for mortars, it is necessary to take into account the effect of air temperature on its setting time.

The following data on stones and mortar should be recorded in the work log:

• brand of used stones and solutions

The composition of the solution (according to passports and invoices) and the results of its testing by a construction laboratory;

• place and time of preparation of the solution;
• delivery time and the state of the solution after transportation when
• centralized preparation and delivery of the solution;
• mortar consistency when laying walls;

Measures that increase the strength of adhesion, carried out during the laying of walls (wetting the brick, cleaning it from dust, ice, laying "under the bay", etc.);

• maintenance of masonry after erection (watering, covering with mats, etc.);
• temperature and humidity conditions during the construction and maturation of masonry.

So, we examined the starting materials for masonry - stones and mortar.

Now let's formulate the requirements for their joint work in laying the walls of an earthquake-resistant building:

· Masonry should, as a rule, be single-row (chain). It is allowed (preferably with a design seismicity of not more than 7 points) multi-row masonry with repetition of bond rows at least every three spoon rows;

Bonded rows, including backfill rows, should be laid only from whole stone and brick;

Only whole bricks should be used to lay brick pillars and piers with a width of 2.5 bricks or less, with the exception of cases when an incomplete brick is needed to dress the masonry joints;

• laying in a wasteland is not allowed;

· Horizontal, vertical, transverse and longitudinal joints must be completely filled with mortar. The thickness of horizontal joints should be at least 10 and not more than 15 mm, the average within the floor - 12 mm; vertical - not less than 8 and not more than 15 mm, average - 10 mm;

· Laying should be carried out for the entire thickness of the wall in each row. At the same time, verst rows should be laid using the "press" or "butt with trimming" methods (the "butt" method is not allowed). For thorough filling of vertical and horizontal masonry joints, it is recommended to perform "under the bay" with a mortar mobility of 14 ... 15 cm.

The spill of the solution in a row is carried out with a scoop.

To avoid loss of mortar, laying is carried out using inventory frames protruding above the row mark to a height of 1 cm.

The solution is leveled using a rail, for which a frame serves as a guide. The speed of movement of the rail when leveling the solution spilled along the row should ensure that it enters the vertical seams. The consistency of the solution is controlled by the bricklayer using an inclined plane located at an angle of approximately 22.50 to the horizon; the mixture should merge from this plane. When laying a brick, the bricklayer must press and tap it, making sure that the distances for vertical joints do not exceed 1 cm.

During a temporary stop in the production of work, the top row of masonry should not be poured with mortar. Continuation of work, as already noted, must begin with watering the surface of the masonry;

· vertical surfaces of furrows and channels for monolithic reinforced concrete inclusions (they will be discussed below) should be performed with trimming the solution by 10...15 mm;

· masonry walls in places of their mutual adjoining should be erected only simultaneously;

Pairing of walls thin in 1/2 and 1 brick with walls of greater thickness when erecting them at different times by means of grooves is not allowed;

Temporary (assembly) gaps in the masonry being erected should only end with an inclined shtraba and be located outside the places of constructive reinforcement of the walls (reinforcement will be discussed below).

Performed in this way (taking into account the requirements for stones, mortar and their joint work), the masonry must acquire the normal adhesion necessary for the perception of seismic effects (temporary resistance to axial tension along untied seams). Depending on the value of this value, masonry is subdivided into category I masonry with 180 kPa and category II masonry with 180 kPa > 120 kPa.

If it is impossible to obtain at the construction site (including mortars with additives) an adhesion value equal to or greater than 120 kPa, the use of brick and stone masonry is not allowed. And only with an estimated seismicity of 7 points is it possible to use natural stone masonry at less than 120 kPa, but not less than 60 kPa. In this case, the height of the building is limited to three floors, the width of the walls is assumed to be at least 0.9 m, the width of the openings is not more than 2 m, and the distance between the axes of the walls is not more than 12 m.

The value is determined by the results of laboratory tests, and the projects indicate how to control the actual adhesion on the construction site.

Control of the strength of the normal adhesion of mortar to brick or stone should be carried out in accordance with GOST 24992-81 "Masonry structures. Method for determining the adhesion strength in masonry".

Wall sections for control are selected at the direction of the representative of technical supervision. Each building must have at least one lot per floor with a separation of 5 stones (bricks) on each lot.

Tests are carried out 7 or 14 days after the end of laying.

On the selected section of the wall, the upper row of masonry is removed, then around the tested stone (brick) with the help of scrapers, avoiding shocks and shocks, they clear the vertical seams into which the grips of the test installation are inserted.

During the test, the load shall increase continuously at a constant rate of 0.06 kg/cm2 per second.

The axial tensile strength is calculated with an error of 0.1 kg/cm2 as the arithmetic mean of the results of 5 tests. The average strength of normal adhesion is determined by the results of all tests in the building and should be at least 90% of the required by the project. In this case, the subsequent increase in the strength of normal adhesion from 7 or 14 days to 28 days is determined using a correction factor that takes into account the age of the masonry.

Simultaneously with the test of the masonry, the compressive strength of the solution is determined, taken from the masonry in the form of plates with a thickness equal to the thickness of the seam. The strength of the solution is determined by testing the compression of cubes with ribs 30 ... 40 mm, made of two plates glued together with a thin layer of gypsum dough 1..2 mm.

Strength is determined as the arithmetic mean of tests of 5 samples.

When performing work, it is necessary to strive to ensure that the normal adhesion and compressive strength of the mortar in all walls and especially along the height of the building are the same. Otherwise, various deformations of the walls are observed, accompanied by horizontal and oblique cracks in the walls.

According to the results of the control of the strength of the normal adhesion of the mortar with brick or stone, an act is drawn up in a special form (GOST 24992-81).

So, in earthquake-resistant construction, masonry of two categories can be used. In addition, according to seismic resistance, masonry is divided into 4 types:

1. Integrated masonry construction.

2. Masonry with vertical and horizontal reinforcement.

3. Masonry with horizontal reinforcement.

4. Masonry with reinforcement only of wall junctions.

The complex construction of the masonry is carried out by introducing vertical reinforced concrete cores into the body of the masonry (including at the intersections and junctions of walls), anchored in anti-seismic belts and foundations.

Brick (stone) laying in complex structures should be carried out on a mortar grade of at least 50.

Cores can be monolithic and prefabricated. Concrete of monolithic reinforced concrete cores must be at least class B10, prefabricated - B15.

Monolithic reinforced concrete cores should be arranged open on at least one side to control the quality of concreting.

Prefabricated reinforced concrete cores have a surface corrugated on three sides, and on the fourth - an unsmoothed concrete texture; moreover, the third surface should have a corrugated shape, shifted relative to the corrugation of the first two surfaces so that its cutouts fall on the protrusions of adjacent faces.

The cross-sectional dimensions of the cores are usually not less than 250x250 mm.

Recall that the vertical surfaces of the channels in the masonry for monolithic cores should be made with trimming the joint solution by 10 ... 15 mm or even with dowels.

First, the cores are placed - the frames of the openings (monolithic - directly at the edges of the openings, prefabricated - with a retreat of 1/2 brick from the edges), and then ordinary ones - symmetrically relative to the middle of the width of the wall or partition.

The pitch of the cores must be no more than eight wall thicknesses and not exceed the floor height.

Monolithic frame-cores must be connected to the masonry walls by means of steel meshes of 3 ... 4 smooth (class A240) rods with a diameter of 6 mm, overlapping the cross section of the core and launched into the masonry at least 700 mm on both sides of the core into horizontal seams through 9 rows of bricks (700 mm) in height with a design seismicity of 7-8 points and through 6 rows of bricks (500 mm) with a design seismicity of 9 points. The longitudinal reinforcement of these meshes must be securely connected with clamps.

From monolithic ordinary cores, closed clamps from d 6 A-I are produced into the partition: if the ratio of the height of the partition to its width is more than 1 (even better - 0.7), i.e. when the partition is narrow, the clamps are issued for the entire width of the partition on both sides of the core, with the specified ratio less than 1 (better - 0.7) - at a distance of at least 500 mm on both sides of the core; the step of the clamps in height is 650 mm (through 8 rows of bricks) with a design seismicity of 7-8 points and 400 mm (through 5 rows of bricks) with a design seismicity of 9 points.

The longitudinal reinforcement of the core is symmetrical. The amount of longitudinal reinforcement is not less than 0.1% of the wall cross-sectional area per one core, while the amount of reinforcement should not exceed 0.8% of the concrete core cross-sectional area. Reinforcement diameter - not less than 8 mm.

For joint work of prefabricated cores with masonry, brackets d 6 A240 are clamped in the corrugated cutouts in each row of masonry, which go into the seams on both sides of the core by 60 ... 80 mm. Therefore, the horizontal seams must match the recesses on the two opposite faces of the core.

There are walls of a complex structure that form and do not form a "clear" frame.

A fuzzy frame of inclusions is obtained when only a part of the walls needs to be reinforced. In this case, the inclusions on different floors can be located differently in the plan.

6, 5, 4 when laying the 1st category and

5, 4, 3 when laying the II category.

In addition to the maximum number of storeys, the maximum height of the building is also regulated.

The maximum permitted height of a building is easy to remember as follows:

n x 3 m + 2 m (up to 8 floors) and

n x 3 m + 3 m (9 or more floors), i.e. 6 floor (20 m); 5 floor (17 m); 4th floor (14 m); 3rd floor (11 m).

I note that the difference between the marks of the lowest level of the blind area or the planned surface of the earth adjacent to the building and the top of the outer walls is taken as the height of the building.

It is important to know that the height of buildings of hospitals and schools with an estimated seismicity of 8 and 9 points is limited to three above-ground floors.

You can ask: if, for example, with a design seismicity of 8 points n max = 4, then with H floor max = 5 m, the maximum height of the building should be 4x5 = 20 m, and I give 14 m.

There is no contradiction here: it is required that the building has no more than 4 floors, and that at the same time the height of the building does not exceed 14 m (which is possible if the floor height in a 4-storey building is not more than 14/4 = 3.5 m). If the floor height exceeds 3.5 m (for example, it reaches H floor max = 5 m), then there can be only 14/5 = 2.8 such floors, i.e. 2. Thus, three parameters are simultaneously regulated - the number of floors, their height and the height of the building as a whole.

In brick and stone buildings, in addition to external longitudinal walls, there must be at least one internal longitudinal wall.

The distance between the axes of the transverse walls with a design seismicity of 7, 8 and 9 points should not exceed, respectively, when laying the I-th category 18.15 and 12 m, when laying the II-th category - 15, 12 and 9 m. The distance between the walls of the complex structure (i.e. type 1) can be increased by 30 .

When designing complex structures with a clear frame, reinforced concrete cores and anti-seismic belts are calculated and designed as frame structures (columns and crossbars). Brickwork is considered as the filling of the frame, which is involved in the work on horizontal influences. In this case, the slots for concreting monolithic cores must be open at least on both sides.

We have already talked about the cross-sectional dimensions of the cores and the distances between them (pitch). With a core spacing of more than 3 m, and also in all cases with a filling masonry thickness of more than 18 cm, the upper part of the masonry must be connected to the anti-seismic belt with short pieces 10 mm in diameter coming out of it in increments of 1 m with a launch into the masonry to a depth of 40 cm.

The number of floors with such a complex wall design is taken no more than with a design seismicity of 7, 8 and 9 points, respectively:

9, 7, 5 when laying the 1st category and

7, 6, 4 when laying the second category.

In addition to the maximum number of storeys, the maximum height of the building is also regulated:

9 floor (30 m); 8 floor (26 m); 7 floor (23 m);

6 floor (20 m); 5 floor (17 m); 4th floor (14 m).

The height of the floors with such a complex wall structure should be no more than 6, 5 and 4.5 m, respectively, with a design seismicity of 7, 8 and 9 points, respectively.

Here, all our reasoning about the "discrepancy" between the limit values ​​of the number of floors and the height of the building, which we conducted about buildings with a complex wall structure with a "fuzzy" pronounced frame, remains valid: for example, with a design seismicity of 8 points n max = 6,

H floor max \u003d 5 m, the maximum height of the building should be 6x5 \u003d 30 m, and the Norms limit this height to 20 m, i.e. in a 6-storey building, the floor height should be no more than 20/6 = 3.3 m, and if the floor height is 5 m, then the building can only be 4-storey.

The distance between the axes of the transverse walls with a design seismicity of 7, 8 and 9 points should not exceed 18, 15 and 12 m, respectively.

Masonry with vertical and horizontal reinforcement.

Vertical reinforcement is taken according to the calculation for seismic effects and is installed in increments of not more than 1200 mm (through 4 ... 4.5 bricks).

Regardless of the results of the calculation in walls with a height of more than 12 m with a design seismicity of 7 points, 9 m with a design seismicity of 8 points and 6 m with a design seismicity of 9 points, vertical reinforcement should have an area of ​​at least 0.1% of the masonry area.

Vertical reinforcement must be anchored in anti-seismic belts and foundations.

The step of horizontal grids is not more than 600 mm (through 7 rows of bricks).

Gyrdymova N.A. and others. USE 2010. Russian language. Universal Directory (Document)

Zhukov E.F. etc. Money. Credit. Banks (Document)

Kurukin I.V., Shestakov V.A., Chernova M.N. USE. Story. Universal Directory (Document)

Skubachevskaya L.A., etc. USE. Literature. Universal Directory (Document)

Grinchenko N.A., Karpenko E.V., Omelyanenko V.I. USE 2010. English. Universal Directory (Document)

(Document)

Abelmas N.V. Universal Guide to Public Relations (Document)

Course project - universal workshop (course course)

n1.rtf

In the production of brickwork in seismic areas it is necessary to impose increased requirements on the quality of the used wall stone materials and mortar. Stone, brick or block surfaces must be free of dust before laying. Portland cement should be used as a binder in masonry mortars.

Prior to the start of stone work, the construction laboratory determines the optimal ratio between the pre-wetting value of the local wall stone material and the water content of the mortar mixture. Solutions are used with high water-retaining capacity (water separation is not more than 2%). The use of cement mortars without plasticizers is not allowed.

Masonry of bricks and ceramic slotted stones is carried out in compliance with the following additional requirements: masonry of stone structures is erected for the entire thickness of the structures in each row; horizontal, vertical, transverse and longitudinal joints of the masonry are completely filled with mortar with trimming of the mortar on the outer sides of the masonry; masonry walls in places of mutual adjacency are erected simultaneously; bonded rows of masonry, including backfilling, are laid out from whole stone and brick; temporary (assembly) gaps in the masonry being erected end with an inclined shtraba and are located outside the places of constructive reinforcement of the walls.

When reinforcing brickwork (pillars), it is necessary to ensure that the thickness of the joints in which the reinforcement is located exceeds the diameter of the reinforcement by at least 4 mm, while observing the average joint thickness for this masonry. The diameter of the wire of transverse meshes for reinforcing masonry is allowed not less than 3 and not more than 8 mm. With a wire diameter of more than 5 mm, a zigzag mesh should be used. The use of individual rods (laid mutually perpendicular in adjacent seams) instead of bound or welded rectangular meshes or zigzag meshes is prohibited.

To control the laying of reinforcement during mesh reinforcement of pillars and piers, the ends of individual rods (at least two) in each mesh should be released from the horizontal joints of the masonry by 2-3 mm.

During the masonry process, the worker or foreman must ensure that the methods of fixing the girders, beams, decks and floor panels in the walls and on the pillars are consistent with the project. The ends of the split girders and beams resting on the internal walls and pillars must be connected and embedded in the masonry; according to the project, reinforced concrete or metal linings are laid under the ends of the runs and beams.

When laying ordinary or wedge-shaped lintels, only selective whole bricks should be used and mortar grade 25 and higher should be used. Lintels are embedded in the walls at a distance of at least 25 cm from the slope of the opening. Under the bottom row of bricks, stacked iron or steel wire with a diameter of 4–6 mm is placed in a mortar layer at the rate of one rod with a cross section of 0.2 cm 2 for each part of the lintel half a brick thick, unless the project provides for stronger reinforcement.

When laying the cornice, the overhang of each row should not exceed 1/3 of the length of the brick, and the total extension of the cornice should not exceed half the thickness of the wall. Eaves with a large extension should be reinforced or run on reinforced concrete slabs, etc., reinforcing them with anchors embedded in the masonry.

Brickwork of walls must be carried out in accordance with the requirements of SNiP III-17-78. During the production of brickwork, acceptance is carried out according to the act of hidden work. Hidden works subject to acceptance include: completed waterproofing; installed fittings; masonry areas in the places where girders and beams are supported; the installation of embedded parts - ties, anchors, etc.; fixing cornices and balconies; corrosion protection of steel elements and parts embedded in masonry; sealing the ends of girders and beams in walls and pillars (presence of base plates, anchors and other necessary details); sedimentary seams; support of floor slabs on walls, etc.
Supervision of stone work in winter

The main method of producing brickwork in winter conditions is freezing. Laying in this way is carried out in the open air using cold bricks and heated mortar, while freezing of the mortar is allowed some time after it has been compressed with a brick.

Electrical heating of winter masonry has not found distribution. Masonry in greenhouses is used as an exception in the construction of foundations or basement walls from rubble concrete. Masonry with the use of fast-hardening mortars prepared on a mixture of Portland cement with aluminous cement is rarely used in construction practice due to the scarcity of aluminous cement. Solutions with additions of sodium chloride or calcium are not used for laying the walls of residential buildings, as they cause increased humidity in buildings. Currently, chemical additives are used for building mortars - sodium nitrite, potash and complex chemical additives - calcium nitrite with urea (NKM - finished product), etc. In this case, the grade of the solution is assigned 50 and higher.

When controlling the construction of masonry by the method of freezing, it should be taken into account that early freezing of mortars in the joints leads to a change in the properties of brickwork compared to masonry walls in the summer. The strength and stability of winter masonry during the thawing period are sharply reduced. The foreman of the masons must ensure that the brick is cleared of snow and ice before laying. For masonry, cement, cement-lime or cement-clay mortars are used. The brand of solutions must be assigned in accordance with the recommendations of the project, as well as taking into account the outside temperature: at an average daily air temperature of up to -3 ° C - a solution of the same brand as for summer masonry; at temperatures from -4 to -20 ° C - the grade of the solution increases by one; at temperatures below -20 ° C - by two.

During brickwork by freezing, the temperature of the mortar when it is used depends on the outside temperature, as shown in Table. 1.37.

Table 1.37

Outside air temperature, °Сup to -10From -11 to -20Below -20Solution temperature, °С101520

Solutions should be prepared on insulated mortar units using hot water (up to 80°C) and heated sand (not higher than 60°C). To reduce the freezing point of the solution, it is recommended to introduce sodium nitrite in the amount of 5% by weight of mixing water into its composition.

At the workplace, the solution should be stored in insulated boxes with lids, and at air temperatures below -10 ° C - heated through the bottom and walls of the consumable boxes using tubular electric heaters. It is forbidden to warm a seized or frozen solution with hot water and put it into action.

When laying by pressing, it is recommended to spread the mortar for no more than every two verst bricks or for 6–8 bricks for backfilling. The thickness of the horizontal joints is no more than 12 mm, since with a greater thickness, strong settlement of the walls during the spring thaw is possible. Laying is carried out in full horizontal rows, i.e. without prior laying of the outer verst, to a height of several rows.

The speed of laying bricks in winter should be high enough so that the mortar in the underlying layers of masonry is compacted by the overlying rows before freezing. Therefore, more workers should work on each patch than in summer. By the break in work, the vertical seams must be filled with mortar. During breaks, it is recommended to cover the masonry with roofing paper, plywood; when resuming work, the top layer of masonry should be thoroughly cleaned of snow and ice.

Freeze masonry in spring can give a large and uneven draft, therefore, over window and door frames installed in the walls, clearances for draft of at least 5 mm should be left. Sedimentary seams must be made at the junction of walls more than 4 m high, erected in winter, to summer masonry walls, to old structures. Lintels above the openings in the walls, as a rule, are made of precast concrete elements. With spans less than 1.5 m, it is allowed to arrange ordinary brick lintels, while the formwork can be removed no earlier than after 15 days. after complete thawing of the masonry.

After the erection of walls and pillars within the floor, the master must ensure that prefabricated floor elements are immediately laid. The ends of the beams and girders, resting on the walls, are fastened with the masonry of the walls after 2-3 m with metal ties fixed in the vertical longitudinal seams of the masonry. The ends of split girders or floor slabs supported by poles or a longitudinal wall are tied with overlays or anchors.

To give the brickwork, erected by freezing, the required stability in the corners of the outer walls and in the places where the inner walls adjoin the outer walls, steel ties are laid. Ties should be inserted into each of the adjoining walls by 1–1.5 m and terminated at the ends with anchors. In buildings with a height of 7 or more floors, steel ties are laid at the level of the floors of each floor, in buildings with a lower number of storeys - at the level of the floors of the second, fourth and each overlying floor.

In some cases, the freezing method is combined with heating the erected building by isolating it from the outside air and connecting the heating system or installing special air heaters. As a result of this, the temperature of the internal air rises, the brickwork thaws, the mortar in it hardens, then the masonry dries up and it is possible to start interior finishing work.

At a positive outside temperature, the masonry thaws. During this period, its strength and stability are sharply reduced and the draft increases. The foreman and the foreman must observe the magnitude, direction and degree of uniformity of the masonry settlement. When thawing the masonry, the work foreman must personally check the condition of all stressed sections of the masonry, as well as ensure that previously left nests, strokes and other holes are laid. With the onset of thaws, random loads (for example, remnants of building materials) should be removed from the floors.

During the entire period of thawing, the masonry made by the freezing method must be carefully controlled and measures taken to ensure the stability of the erected structures. If signs of overvoltage are detected (cracks, uneven settlements), measures should be taken immediately to reduce the load. In such cases, as a rule, temporary unloading racks are installed under the ends of the bearing elements (for example, ceilings, lintels). Temporary racks in multi-storey buildings are installed not only in the unloaded span or masonry opening, but also in all underlying floors in order to avoid overloading the latter.

In case of detection of deviation of thawing walls and pillars from the vertical or cracks in the places where the transverse walls adjoin the longitudinal ones, in addition to temporary fastenings, braces and extensions are immediately installed to eliminate the possibility of displacement development. With significant displacements, tension ropes, clamps, struts are installed to bring the displaced elements to the design position. This should be done before the mortar hardens in the joints, usually no later than five days after the start of thawing of the masonry.

To increase the bearing capacity of brick walls and ensure the spatial rigidity of the entire building in the spring, artificial thawing of the masonry is used, which is carried out by heating the building with closed openings in the walls and ceilings, which can be recommended for buildings to be finished before spring warming. In addition, artificial thawing is used for load-bearing brick walls with solid monolithic reinforced concrete floors, resting along the perimeter on these walls, and inside - on reinforced concrete or metal columns of constant height. For artificial thawing, portable oil and gas heaters can be used, with the help of which the temperature in the premises is raised to 30–50 ° C and maintained for 3–5 days. Then within 5-10 days. at a temperature of 20–25 ° C and enhanced ventilation, the walls are dried. After that, using a stationary heating system, the walls of the building are dried to a moisture content of the solution of not more than 8%, and only then they begin finishing work. By the end of heating, the strength of the mortar in the masonry must be at least 20% of the branded strength.

During the spring thaw period, the construction laboratory must systematically monitor the increase in the strength of the winter masonry mortar. In accordance with the instructions of the author's supervision, in several places of the brickwork, the laboratory assistant selects samples-plates with a size of at least 50x50 mm from horizontal joints. It is best to take them under window openings; for this, two rows of bricks are removed and, using a special spatula or trowel, the mortar plate is separated from the brick.

The samples, together with the accompanying act, are sent to the construction laboratory for testing. The accompanying act indicates the number of storeys and the structure of the building, the thickness of the walls and the location of the sampling site, as well as the time of work, the date of sampling and the design grade of the solution. Samples of winter frozen solutions intended to determine the strength at the time of thawing are stored at a negative temperature.

From samples of the solution delivered to the laboratory, cube samples with an edge of 20–40 mm are made or, according to the method of engineer Senyuta, plates in the form of a square, the sides of which are approximately 1.5 times greater than the thickness of the plate, equal to the thickness of the seam. To obtain cubes, two plates are glued together with a thin layer of gypsum, which is also used to level the supporting surface of the cube sample when testing mortar from summer masonry joints.

The strength of winter masonry solutions at the time of thawing is determined by a compression test, leveling the surfaces of the plates instead of gypsum dough by rubbing with a carborundum bar, rasp, etc. The testing of samples in this case should be carried out after the solution has been thawed for 2 hours in the laboratory at a temperature of 18–20°C. The load on the plate is transmitted through a 20–40 mm metal rod installed in the middle. The sides of the base or the diameter of the rod should be approximately equal to the thickness of the plate. Given the deviations in the thickness of the plates, it is recommended to have a set of rods with different cross sections and diameters during testing.

The compressive strength of the mortar is determined by dividing the breaking load index by the cross-sectional area of ​​the rod. From each sample, five samples are tested and the arithmetic mean value is determined, which is considered to be an indicator of the strength of the solution of this sample. To go to the strength of the solution in cubes with an edge of 70.7 mm, the test results for the plates are multiplied by a factor of 0.7.

The test results of cube samples with an edge of 30-40 mm, glued from plates and leveled with a gypsum layer 1-2 mm thick, are multiplied by a factor of 0.65, and the test results of plates, also lined with gypsum, by a factor of 0.4. For summer masonry, these coefficients are taken equal to 0.8 and 0.5, respectively.

To test the strength of mortar samples, lever devices are used that fix the strength with an error of up to 0.2 MPa, as well as RMP-500 and RM-50 tensile machines with reversers. These mortar tests help to develop the necessary measures in time to ensure the stability of the brickwork during the period of complete thawing.
Defects of stone structures and methods for their elimination

The causes of defects in stone structures are different: uneven settlement of individual parts of buildings; design errors associated with the use of wall materials of different strength and rigidity (for example, ceramic blocks together with silicate bricks) that have different physical, mechanical and elastic properties; the use of wall materials that do not meet the requirements of current standards in terms of strength and frost resistance; low quality of stone work, etc. To eliminate sediment caused by the removal of soil from under the foundation, the gaps between the base and the foundation are usually filled with soil, followed by compaction with deep vibrators. In some cases, to prevent the complete destruction of the masonry, reinforced concrete piles are placed under all load-bearing walls.

The combined use of ceramic cladding stones and silicate bricks in loaded piers of multi-storey residential buildings led to the appearance of cracks, the cladding of piers bulged out and then collapsed.

The use of brick, the strength of which is lower than that provided for by the project, and a mortar of poor quality or diluted after setting, significantly reduces the strength and solidity of the masonry and can lead to deformation and collapse of stone structures.

One of the main causes of defects in stone structures is the unsatisfactory quality of stone work. The most frequent are such masonry defects as thickened joints, hollows more than 2 cm deep, absence or incorrect mesh reinforcement, deviations from the project when arranging support nodes for girders on pillars or walls, etc. The presence of hollows leads to the fact that brick in stone structures begins to work in bending, and its strength when working in bending is much lower than in compression. There are cases when the grids of reinforcement with a diameter of 3-4 mm provided for by the project are replaced with grids of reinforcement with a diameter of 5-6 mm, believing that such a replacement will increase the bearing capacity of the masonry. However, in this case, the brick does not lie on a bed of mortar, but on bars, therefore, significant local crushing stresses appear in it, which lead to the appearance of a large number of vertical cracks in the masonry.

When checking the quality of masonry with mesh reinforcement, one has to deal with such facts when the meshes are not laid according to the project, with large gaps, or individual rods are laid instead of the meshes, which in no case can replace the welded mesh.

In cases where cracks are found in the masonry during inspection, it is necessary to identify and eliminate the causes that cause them, and then make sure that the deformation of the walls is over. Geodetic devices and instruments, string, glass and other beacons are used to fix the sediment of the structure and control the development of cracks. In the absence of ready-made lighthouses at the construction site, they can be made on site from building gypsum. To do this, prepare a solution of the composition 1: 1 (gypsum: sand) of such a consistency that when applied to the wall it does not drain. If the brick walls are plastered, then in the places where the lighthouses are installed, the plaster is knocked down, the seams of the masonry are cleaned, cleaned of dust and washed with water. It is impossible to put beacons on uncleaned and unwashed masonry, because due to weak adhesion to it, an increase in the opening of cracks in the masonry will not be recorded. Gypsum beacons are made 5-6 cm wide and about 20 cm long. The length of the beacons is specified on the spot, depending on the nature of the development of cracks. The thickness of the beacon is usually 10–15 mm.

Lighthouses are numbered and the installation date is written on them. In the observation log, the following is recorded: the location of the beacon, its number, the date of installation, the initial width of the crack. The state of the lighthouses is systematically monitored (at least once a day), and these observations are recorded in a log. If the beacon breaks, a new one is installed next to it, which is given the same number with an index. In the event of repeated deformation (rupture) of the beacons, it is necessary to immediately take measures to prevent the possibility of unexpected settlement or even collapse of the structure. If three or four weeks after the installation of the beacons, their rupture did not follow, it means that the deformation in the controlled structure has stopped and the cracks can be repaired. Separate small cracks are cleared of dirt and dust and rubbed with a 1: 3 cement mortar on Portland cement grades 400–500.

Larger cracks (wider than 20 mm) are repaired by disassembling part of the old masonry and replacing it with a new one. When sealing cracks in walls up to one and a half bricks thick, disassembly and sealing of masonry are performed sequentially in separate sections for the entire thickness of the wall in the form of brick locks. If the width of the cracks is significant (more than 40 mm), then anchors or metal ties are placed to fasten the masonry.

The strength of old brick walls, as well as walls and piers made with a significant wasteland, can be increased by injecting a liquid mortar or cement laitance into the masonry. Construction practice has shown that brick pillars as load-bearing structures do not justify themselves: some pillars in the upper floors have a significant offset relative to the pillars in the lower floors. When using a hard mortar, the thickness of the seams turns out to be greater than the design one, many empty seams appear and the adhesion of the mortar to the brick is insufficient, which ultimately affects the solidity of the erected pillars. In many cases it was necessary to reinforce most of the brick pillars. The most common way to gain is to take them in a clip.

Depending on the degree of damage to the masonry and the production capabilities, the clips can be made of cement plaster on a steel mesh, of brick with steel clamps in the seams, of reinforced concrete, of steel.

In cases where reinforcement should be performed without a significant increase in the dimensions of the cross-section of the pillars, it is recommended to make the clip from cement plaster on a steel mesh. The mesh consists of a series of clamps with a pitch of 150–200 mm, interconnected by longitudinal reinforcement with a diameter of 8–10 mm. According to the grid formed in this way, plaster is made from a cement mortar with a composition of 1: 3 (by volume), 20–25 mm thick.

Brick clips are distinguished by ease of execution, however, their arrangement leads to a significant increase in the cross-sectional dimensions of the reinforced elements. Clips of this type are made of bricks on the edge with reinforcement of the masonry seams with steel clamps with a diameter of 10–12 mm.

To increase the bearing capacity of stone pillars, reinforced concrete clips are used. In this case, the thickness of the clip, as a rule, is taken as 8–10 cm. Clamps and longitudinal steel reinforcement with a diameter of 10–12 mm are attached to the reinforced pillars, after which they are poured with concrete of grade M100 and higher.

Strengthening brick pillars with steel clips requires a lot of metal, but this can significantly increase their bearing capacity. Such reinforcement often has to be done for the walls of the first floor in cases where the poor quality of the brickwork has led to the appearance of cracks in them.

In case of violation of the adhesion of the facing layer of ceramic blocks with brickwork, it is possible to undertake a general strengthening of the masonry and cladding by injecting seams and voids in the masonry, as well as cracks and places of peeling of the cladding. To do this, tubes are installed in the seams between the facing ceramic stones, through which a liquid cement mortar with a composition of 1: 3 (by volume) is supplied. It is necessary to control the amount of injected solution and the radius of its distribution. The latter is easy to install by the appearance of spots on the internal plaster of the walls.

To strengthen the lining and protect it from sudden delamination, it can be fixed with steel pins. Holes with a diameter of 25 mm to a depth of 25–30 cm are drilled in the walls at an angle of up to 30 °, into which steel pins are laid flush with the lining on the mortar. In order to avoid accidents, it is necessary to develop projects for strengthening stone structures as soon as possible and to carry out all the work prescribed by the designer's supervision under the direct control of the work manufacturer. Upon completion, an act is drawn up for the performance of work to strengthen stone structures.
Acceptance of stone works

In the process of acceptance of stone structures, the volume and quality of work performed, the compliance of structural elements with working drawings and the requirements of SNiP III-17-78 are established.

Throughout the entire period of work, representatives of the construction organization and the technical supervision of the customer carry out the acceptance of hidden work and draw up relevant acts.

When accepting stone structures, the quality of materials used, semi-finished products and factory-made products is established according to passports, and the quality of mortars and concretes prepared at construction is determined according to laboratory tests. In cases where the applied stone materials were subjected to a control check in a construction laboratory, the results of these laboratory tests must be submitted for acceptance.

During the acceptance of finished stone structures, the following are checked:

- the correctness of transportation, the thickness and filling of the seams;

- verticality, horizontality and straightness of masonry surfaces and corners;

- the correctness of the device of sedimentary and temperature seams;

- the correct arrangement of smoke and ventilation ducts;

- the presence and correct installation of embedded parts;

- the quality of the surfaces of facade non-plastered brick walls (evenness of color, observance of dressing, pattern and jointing);

- the quality of facade surfaces lined with various kinds of slabs and stones;

- ensuring the removal of surface water from the building and protection of foundations and basement walls from them.

Controlling the quality of stone structures, they carefully measure deviations in the size and position of structures from the design ones and make sure that the actual deviations do not exceed the values ​​\u200b\u200bspecified in SNiP III-17-78. Permissible deviations are given in table. 1.38.

Acceptance of arches, vaults, retaining walls and other especially critical stone structures is drawn up in separate acts. If, during the production of stone work, reinforcement of individual structures was performed, then upon acceptance, working drawings of the reinforcement and a special act for the work performed to strengthen the stone structures are presented. When accepting stone structures made in winter, a winter work log and acts for hidden work are presented.

Table 1.38

Permissible deviations in the dimensions and positions of structures made of bricks, ceramic and natural stones of the correct form, from large blocks

Permissible deviationsWallsPillarsFoundationsDeviations from design dimensions: by thickness 151030 by marks of cutoffs and floors–10–10–25 by the width of piers–15–by the width of openings15–by the displacement of the axes of adjacent window openings10–by the displacement of the axes of structures101020 Deviations of surfaces and corners of masonry from the vertical: by one floor 1010 – for the whole building

Process Control Cards

Brickwork pillars

SNiP III-17-78, tab. 8, pp. 2.10, 3.1, 3.5, 3.15

Permissible deviations: according to the marks of cutoffs and floors - 15 mm; in thickness - 10 mm. Allowed: thickness of vertical joints - 10 mm (thickness of individual vertical joints - not less than 8 and not more than 15 mm); thickness of horizontal seams - not less than 10 and not more than 15 mm. The stitching system for poles is three-row.

Permissible deviations: for the displacement of the axes of structures - 10 mm; masonry surfaces and angles from the vertical to one floor - 10 mm, to the entire building - 30 mm; the vertical surface of the masonry from the plane when applying a 2-meter rail - 5 mm.

The depth of joints not filled with mortar (only vertical ones) on the front side is allowed no more than 10 mm. When laying poles, it is not allowed to use individual rods instead of connected or welded rectangular meshes or zigzag meshes.

In table. 1.39 shows the operations to be controlled during the construction of pillars.

Hidden works include the following: brickwork of pillars (marks of cutoffs and floors, the correct arrangement of the pillow under the beams, the support of the beams on the pillows and their embedding in the masonry).

Table 1.39

Supervision of work during bricklaying of pillars

Operations to be controlled Composition of control (what to control) Method of control Time of control Who controls and is involved in the inspection Preparatory work Quality of the base for the pillars, the presence of waterproofing Visually Before laying Master Quality of bricks, mortar, reinforcement, embedded parts Visually, measurement, checking passports and certificates Before laying Master. In case of doubt, the laboratory Correct binding of posts to the staking axes Visually, construction plumb line Before the start of laying Foreman Brick laying of pillars Dimensions, filling and bandaging of joints Folding metal meter After every 5 m of laying Master Geometrical dimensions of the section Folding metal meter In the process of masonry Master Verticality of laying, unevenness on the surface , folding metal meter At least twice on each tierMaster Correct masonry technology and dressing of seams Visually During masonry Foreman Correspondence of the actual position of the pillars to the design (axis).
Alignment of pillars of different floors Construction plumb line, folding metal meter During masonry Foreman Marks of cutoffs and floors, correct arrangement of the pillow under the beams, support of the beams on the pillows and their embedding in the masonry Visually, level, folding metal meter After the pillow is installed and the beam is installed Foreman, surveyor nets along the height of the column. The diameter of the rods and the distance between them Folding metal meter, caliper As the reinforcement is laid, the master

Brickwork walls

SNiP III-B.4-72, tab. 8, pp. 1.9, 2.5, 2.10, 3.5

SNiP III-17-78

Permissible deviations: masonry rows from the horizontal for 10 m of length - 15 mm; masonry surfaces and corners from the vertical: one floor - 10 mm; for the whole building - 30 mm; by offset of the axes of adjacent window openings - 20 mm; on the width of the openings - +15 mm.

Irregularities on a vertical surface are allowed when applying a two-meter rail: non-plastered - 5 mm; plastered - 10 mm.

Permissible deviations: according to the marks of cutoffs and floors - 15 mm; along the width of the walls - 15 mm; by displacement of the axles of structures - 10 mm; on the thickness of the masonry - +10 mm.

Allowed: thickness of horizontal seams - not less than 10 and not more than 15 mm; thickness of vertical joints - 10 mm (thickness of individual vertical joints - not less than 8 and not more than 15 mm).

When laying in a hollow, the depth of the seams not filled with mortar on the front side is allowed no more than 15 mm.

Mortar mixtures must be used before they begin to set. It is not allowed to use dehydrated mixtures. The addition of water to the set mixtures is prohibited. Mixtures that have separated during transportation should be mixed before use.

If the gap in the masonry is performed by a vertical chisel, then structural reinforcement of three rods with a diameter of 8 mm should be laid in the seams of the masonry chisel, every 2 m along the height of the masonry, including at the level of each floor. The operations to be controlled during masonry walls are indicated in Table. 1.40.

Hidden works include the following: masonry of walls (alignment of ventilation ducts and sealing of ventilation blocks); reinforcement of masonry (correct location of reinforcement, diameter of rods); installation of prefabricated reinforced concrete slabs, ceilings (supporting ceilings on walls, embedding, anchorage); installation of balconies (sealing, mark, slope of balconies).

Table 1.40

Supervision of work during bricklaying of walls

Operations to be controlled Composition of control (what to control) Method of control Time of control Who controls and is involved in the inspection Brick laying of walls Quality of bricks, mortar, reinforcement of embedded parts External inspection, measurement, verification of passports and certificates Before laying the walls of the floor Foreman. In case of doubt, the laboratory Correct alignment of the axes Metal tape measure, metal folding meter Before the start of laying Foreman Horizontal marking of masonry cutoffs under the floor Level, rail, building levelBefore installing floor panels Foreman, surveyor Alignment of ventilation ducts and sealing of ventilation blocks Visually, plumb construction , openings) Folding metal meter, metal tape measure After every 10 m 3 masonryMaster Verticality, horizontality and surface of masonry Construction plumb line, rail During and after completionMaster Quality of masonry seams (dimensions and filling) Visually, folding metal meter, 2-meter railAfter masonry walls of the floor every 10 m 3 masonryMaster Breakdown and marks of the bottom of the openingsMetal tape measure, building levelBefore the start of laying the piersMaster Removal from the mark + 1 m from the finished floorLevel After the end of the laying of the floorMaster Layout of the apartmentsVisuallyAfter the start of laying the wallsMaster Geometric dimensions of the premisesMetal tape measure After the start of laying the wallsMaster Reinforcing masonryCorrect location of reinforcement, diameter rods and t. dVisually folding metal meterBefore installation of reinforcementForemanInstallation of prefabricated reinforced concrete slabs, ceilingsSupporting ceilings on walls, sealing, anchoringVisual folding metalmeterAfter installation of ceilingsForemanAnti-corrosion coating of embedded partsThickness, density and adhesion of the coatingVisual thickness gauge, engraving chiselBefore sealingForeman, laboratoryInstallation of balconiesSealing, marking fabric, slope of balconies Visually, folding metal meter , building level, 2-meter railAfter installation of balconiesForemanInstallation of lintelsPosition of lintels, support, placement, terminationVisually, folding metal meterAfter installationMasterInstallation of landingsPosition of landings, support, placement, termination Visually, folding metal meterAfter installation of platforms, lintelsMasterWelding of embedded partsLength, height and quality of welded seamsVisually , tapping with a hammer Before anti-corrosion coating is completed Master

Brick block walls

SNiP III-B.4-72, tab. 8, pp. 3.18, 3.19, 3.21, 3.23

SNiP III-17-78

Permissible deviations of block sizes from the design ones: along the block thickness - plus 5 mm; along the length and height of the block - from plus 5 to 10 mm; by the difference of diagonals - 10 mm; in the position of window and door openings - ± 10 mm; when embedded parts are displaced - ± 5 mm.

Permissible deviations during installation: surfaces and masonry angles from the vertical: one floor - ± 10 mm; full height - ± 30 mm; according to the marks of cutoffs and floors - ± 15 mm; for the displacement of the axes of structures - ± 10 mm; rows of masonry from the horizontal to 10 m in length - 15 mm.

In table. 1.41 indicates the objects and operations subject to control during the construction of walls from brick blocks.

Hidden works include the following: masonry walls made of brick blocks; correct installation of lighthouse blocks at the level of floors; installation of blocks with smoke and ventilation ducts; installation of embedded parts; welding of embedded parts of pipes of sanitary blocks; installation of precast concrete floor slabs.

with a step of the wall columns of the frame no more than 6 m;

with a height of the walls of buildings erected on sites with a seismic activity of 7, 8 and 9 points, respectively, no more than 18, 16 and 9 m.

3.24. The laying of self-supporting walls in frame buildings should be of category I or II (according to clause 3.39), have flexible connections with the frame that do not prevent horizontal displacement of the frame along the walls.

Between the surfaces of the walls and columns of the frame, a gap of at least 20 mm should be provided. Anti-seismic belts connected to the building frame should be installed along the entire length of the wall at the level of the roofing slabs and the top of the window openings.

At the intersections of the end and transverse walls with the longitudinal walls, anti-seismic seams should be arranged for the entire height of the walls.

3.25. Stair and elevator shafts of frame buildings should be arranged as built-in structures with floor-by-floor cuts that do not affect the rigidity of the frame, or as a rigid core that perceives seismic loads.

For frame buildings with a height of up to 5 floors with an estimated seismicity of 7 and 8 points, it is allowed to arrange stairwells and elevator shafts within the building plan in the form of structures separated from the building frame. The device of staircases in the form of separate structures is not allowed.

3.26. As load-bearing structures of tall buildings (more than 16 floors), frames with diaphragms, ties or stiffening cores should be taken.

When choosing structural schemes, preference should be given to schemes in which plasticity zones occur primarily in the horizontal frame elements (crossbars, lintels, strapping beams, etc.).

3.27. When designing high ranks, in addition to bending and shear deformations in the frame racks, it is necessary to take into account axial deformations, as well as the compliance of the bases, and to carry out a calculation for the stability against overturning.

3.28. On sites built with soils of category III (according to Table 1 *), the construction of high knowledge, as well as buildings indicated in pos. 4 tab. 4. not allowed.

3.29. The foundations of tall buildings on non-rocky soils should, as a rule, be taken as piles or in the form of a solid foundation slab.

LARGE PANEL BUILDINGS

3.30. Large-panel knowledge should be designed with longitudinal and transverse walls combined with each other and with ceilings and coatings into a single spatial system that perceives seismic loads.

When designing large-panel buildings, it is necessary:

wall and ceiling panels should be provided, as a rule, the size of the room;

provide for the connection of wall and floor panels by welding the reinforcement outlets, anchor rods and embedded parts and the embedding of vertical wells and joints along horizontal seams with fine-grained concrete with reduced shrinkage;

when the floors are supported on the outer walls of the building and on the walls at the expansion joints, welded joints of the reinforcement outlets from the floor panels with the vertical reinforcement of the wall panels should be provided.

3.31. Reinforcement of wall panels should be performed in the form of spatial frames or welded reinforcing meshes. In the case of using three-layer external wall panels, the thickness of the internal bearing concrete layer should be at least 100 mm.

3.32. The constructive solution of horizontal butt joints should ensure the perception of the design values ​​of the forces in the seams. The required cross-section of metal bonds in the joints between the panels is determined by calculation, but it should not be less than 1 cm2 per 1 m of the joint length, and for buildings 5 ​​floors high or less with a site seismicity of 7 and 8 points, at least 0.5 cm2 per 1 m of length seam. It is allowed to place no more than 65% of the vertical design reinforcement at the intersections of the walls.

3.33. The walls along the entire length and width of the building should, as a rule, be continuous.

3.34. Loggias should be, as a rule, built-in, with a length equal to the distance between adjacent walls. In places where loggias are located in the plane of the outer walls, reinforced concrete frames should be provided.

Bay windows are not allowed.

BUILDINGS WITH BEARING WALLS FROM BRICK OR STONE

3.35. Bearing brick and stone walls should be built, as a rule, from brick or stone panels or blocks manufactured in the factory using vibration, or from brick or stone masonry with mortars with special additives that increase the adhesion of mortar to brick or stone.

With an estimated seismicity of 7 points, it is allowed to erect bearing walls of buildings from masonry on mortars with plasticizers without the use of special additives that increase the adhesion strength of the mortar to brick or stone.

3.36. Performing brick and stone masonry manually at a negative temperature for load-bearing and self-supporting walls (including those reinforced with reinforcement or reinforced concrete inclusions) with an estimated seismicity of 9 or more points is prohibited.

With an estimated seismicity of 8 or less points, it is allowed to perform winter masonry manually with the obligatory inclusion of additives in the solution that ensure the hardening of the solution at low temperatures.

3.37. Calculation of stone structures should be carried out for the simultaneous action of horizontally and vertically directed seismic forces.

The value of the vertical seismic load with a design seismicity of 7-8 points should be taken equal to 15%, and with a seismicity of 9 points - 30% of the corresponding vertical static load.

The direction of the vertical seismic load (up or down) should be taken more unfavorable for the stress state of the element under consideration.

3.38. For laying load-bearing and self-supporting walls or filling the frame, the following products and materials should be used:

a) solid or hollow brick of grade not lower than 75 with holes up to 14 mm in size; with an estimated seismicity of 7 points, it is allowed to use ceramic stones of a grade of at least 75;

b) concrete stones, solid and hollow blocks (including lightweight concrete with a density of at least 1200 kg/m3) grade 50 and above;

a) stones or blocks made of shell rocks, limestone of grade at least 35 or tuffs (except for felsic) of grade 50 and above.

Piecework of walls should be carried out on mixed cement mortars of grade not lower than 25 in summer conditions and not lower than 50 in winter. For laying blocks and panels, a mortar grade of at least 50 should be used.

3.39. Masonry, depending on their resistance to seismic effects, are divided into categories.

The category of brick or stone masonry made from the materials specified in clause 3.38. is determined by the temporary resistance to axial stretching along non-tied seams (normal adhesion), the value of which should be within:

To increase normal coupling https://pandia.ru/text/78/304/images/image016_13.gif" width="16" height="21 src="> must be specified in the project..gif" width="18" height="23"> equal to or exceeding 120 kPa (1.2 kgf/cm2), brick or stone masonry is not allowed.

Note..gif" width="17 height=22" height="22"> obtained as a result of tests carried out in the construction area:

R p = 0.45 (9)

R Wed = 0,7 (10)

R ch = 0.8 (11)

Values R R, R Wed and R Ch should not exceed the corresponding values ​​in the destruction of masonry in brick or stone.

3.41. The floor height of buildings with load-bearing walls made of brick or stone masonry, not reinforced with reinforcement or reinforced concrete inclusions, should not exceed 5, 4 and 3.5 m with a design seismicity of 7, 8 and 9 points, respectively.

When reinforcing the masonry with reinforcement or reinforced concrete inclusions, the floor height can be taken equal to 6, 5 and 4.5 m, respectively.

In this case, the ratio of the floor height to the wall thickness should be no more than 12.

3.42. In buildings with load-bearing walls, in addition to external longitudinal walls, as a rule, there must be at least one internal longitudinal wall. The distances between the axes of the transverse walls or frames replacing them must be checked by calculation and be no more than those given in Table 9.

Table 9

	Distances, m, at design seismicity, points

Note. It is allowed to increase the distance between the walls of complex structures by 30% against those indicated in Table 9.

3.43. The dimensions of the elements of the walls of stone buildings should be determined by calculation. They must meet the requirements given in Table. 10.

3.44. At the level of floors and roofs, anti-seismic belts should be installed along all longitudinal and transverse walls, made of monolithic reinforced concrete or prefabricated with monolithic joints and continuous reinforcement. The anti-seismic belts of the upper floor must be connected with the masonry by vertical reinforcement outlets.

In buildings with monolithic reinforced concrete ceilings, embedded along the contour into the walls, it is allowed not to arrange anti-seismic belts at the level of these ceilings.

3.45. An anti-seismic belt (with a supporting section of the floor) should be arranged, as a rule, over the entire width of the wall; in external walls with a thickness of 500 mm or more, the width of the belt can be 100-150 mm less. The height of the belt must be at least 150 mm, the concrete grade 1 must be at least 150.

Anti-seismic belts must have longitudinal reinforcement 4 d l0 with design seismicity of 7-8 points and not less than 4 d 12 - at 9 points.

3.46. In wall junctions, reinforcing meshes with a cross section of longitudinal reinforcement with a total area of ​​​​at least 1 cm2, 1.5 m long, 700 mm in height, with a design seismicity of 7-8 points and 500 mm - with 9 points, should be laid in the masonry.

Wall sections and pillars above the attic floor, having a height of more than 400 mm, must be reinforced or reinforced with monolithic reinforced concrete inclusions anchored in an anti-seismic belt.

Brick pillars are allowed only with a design seismicity of 7 points. In this case, the grade of the solution should not be lower than 50, and the height of the pillars should not exceed 4 m. In two directions, the pillars should be connected with beams anchored into the walls.

3.47. The seismic resistance of the stone walls of the building should be increased by reinforcement meshes, the creation of an integrated structure, the prestressing of the masonry, or other experimentally substantiated methods.

Vertical reinforced concrete elements (cores) must be connected to anti-seismic belts.

Reinforced concrete inclusions in the masonry of complex structures should be arranged open on at least one side.

Table 10

wall element	Wall element size, m, at design seismicity, points	Notes
Walls with a width, not less than, m, when laying:				The width of the corner walls should be taken 25 cm more than indicated in the table. Partitions of smaller width must be reinforced with reinforced concrete framing or reinforcement
2. Openings with a width, not more than, m, when laying I or II category				Openings of greater width should be bordered with a reinforced concrete frame
3. The ratio of the width of the pier to the width of the opening, not less than
4. Protrusion of walls in plan, no more than, m
5. Removal of cornices, no more than, m:				Removal of wooden unplastered
wall material				cornices allowed
from reinforced concrete elements connected with anti-seismic belts
wooden, plastered on a metal mesh

When designing complex structures as frame systems, anti-seismic belts and their junctions with posts should be calculated and designed as elements of frames, taking into account the work of filling. In this case, the grooves provided for concreting the posts must be open at least on both sides. If complex structures are made with reinforced concrete inclusions at the ends of the walls, the longitudinal reinforcement must be securely connected with clamps laid in the horizontal joints of the masonry. The concrete of inclusions must not be lower than grade 150, the gurney must be carried out on a mortar of grade not lower than 50, and the amount of longitudinal reinforcement should not exceed 0.8% of the sectional area of ​​the concrete of the piers.

Note. The bearing capacity of reinforced concrete inclusions located at the ends of the walls, taken into account when calculating for seismic action, should not be taken into account when calculating sections for the main combination of loads.

3.48. In buildings with load-bearing walls, the first floors used for shops and other premises requiring a large free area should be made of reinforced concrete structures.

3.49. Jumpers should be arranged, as a rule, for the entire thickness of the wall and embedded in the masonry to a depth of at least 350 mm. With an opening width of up to 1.5 m, sealing of jumpers is allowed by 250 mm.

3.50. Beams of landings should be embedded in the masonry to a depth of at least 250 mm and anchored.

It is necessary to provide for fastening steps, stringers, prefabricated marches, connection of landings with ceilings. The device of cantilever steps embedded in masonry is not allowed. Door and window openings in the chamber walls of staircases with an estimated seismicity of 8-9 points should, as a rule, have a reinforced concrete frame.

3.51. In buildings with a height of three or more floors with load-bearing walls made of brick or masonry with a design seismicity of 9 points, exits from the stairwells should be arranged on both sides of the building.

REINFORCED CONCRETE STRUCTURES

3.52. When calculating the strength of normal sections of bent and eccentrically compressed elements, the limiting characteristic of the compressed zone of concrete should be taken according to SNiP for the design of concrete and reinforced concrete structures with a coefficient of 0.85.

3.53. In eccentrically compressed elements, as well as in the compressed zone of bending elements with a design seismicity of 8 and 9 points, clamps should be placed according to the calculation at distances: at R ac 400 MPa (4000 kgf / cm2) - no more than 400 mm and with knitted frames - no more than 12 d, and with welded frames - no more than 15 d at R ac ³ 450 MPa (4500 kgf / cm2) - no more than 300 mm and with knitted frames - no more than 10 d, and with welded frames - no more than 12 d, Where d- the smallest diameter of the compressed longitudinal rods. In this case, the transverse reinforcement must ensure the fastening of the compressed rods from their bending in any direction.

The distances between the clamps of eccentrically compressed elements at the points of joining of the working reinforcement with an overlap without welding should be taken no more than 8 d.

If the total saturation of an eccentrically compressed element with longitudinal reinforcement exceeds 3%, the clamps should be installed at a distance of no more than 8 d and not more than 250mm.

3.54. In the columns of frame frames of multi-storey buildings with an estimated seismicity of 8 and 9 points, the step of the clamps (except for the requirements set forth in paragraph 3.53) should not exceed 1/2 h, and for frames with supporting diaphragms - no more h, Where h- the smallest size of the side of the columns of rectangular or I-section. The diameter of the clamps in this case should be taken at least 8 mm.

3.55. In knitted frames, the ends of the clamps must be bent around the longitudinal reinforcement rod and inserted into the concrete core by at least 6 d collar.

3.56. Elements of prefabricated columns of multi-storey frame buildings, if possible, should be enlarged by several floors. Joints of prefabricated columns must be located in an area with lower bending moments. Jointing of longitudinal reinforcement of columns with an overlap without welding is not allowed.

3.57. In prestressed structures subject to calculation for a special combination of loads, taking into account seismic effects, the forces determined from the strength conditions of the sections must exceed the forces perceived by the section during the formation of cracks by at least 25% .

3.58. In prestressed structures, it is not allowed to use reinforcement for which the relative elongation after rupture is below 2%.

3.59. In buildings and structures with a design seismicity of 9 points without special anchors, it is not allowed to use reinforcing ropes and bar reinforcement of a periodic profile with a diameter of more than 28 mm.

3.60. In prestressed structures with reinforcement tensioned on concrete, the prestressed reinforcement should be placed in closed channels, which are later embedded with concrete or mortar.

4. TRANSPORT FACILITIES

GENERAL PROVISIONS

4.1. The instructions of this section apply to the design of railways of categories I-IV, highways of categories I-IV, IIIp and IVp, subways, express city roads and main streets running in areas with seismic activity of 7, 8 and 9 points.

Notes: 1. Production, auxiliary, storage and other buildings for transport purposes should be designed according to the instructions of sections 2 and 3.

2. When designing structures on railways of category V and on railway tracks of industrial enterprises, seismic loads may be taken into account in agreement with the organization approving the project.

4.2. The section establishes special requirements for the design of transport facilities with a design seismicity of 7, 8 and 9 points. Estimated seismicity for transport facilities is determined according to the instructions of clause 4.3.

4.3. Projects of tunnels and bridges with a length of more than 500 m should be developed on the basis of the design seismicity, established in agreement with the organization approving the project, taking into account the data of special engineering and seismological studies.

The design seismicity for tunnels and bridges with a length of not more than 500 m and other artificial structures on railways and roads of categories I-III, as well as on high-speed city roads and main streets is taken equal to the seismicity of construction sites, but not more than 9 points.

Estimated seismicity for artificial structures on railways of categories IV-V, on railway tracks of industrial enterprises and on roads of categories IV, IIIï and IVï, as well as for embankments, excavations, ventilation and drainage tunnels on roads of all categories is taken one point lower than seismicity construction sites.

Note. The seismicity of construction sites for tunnels and bridges no longer than 500 m and other road structures, as well as the seismicity of construction sites for embankments and excavations, as a rule, should be determined on the basis of data from general engineering and geological surveys. according to Table 1*, taking into account the additional requirements set out in clause 4.4.

4.4. During surveys for the construction of transport structures erected on sites with special engineering and geological conditions (sites with complex topography and geology, river channels and floodplains, underground workings, etc.), and when designing these structures, coarse clastic soils of low moisture from igneous rocks containing 30% of sandy-argillaceous filler, as well as gravelly dense and medium-density water-saturated sands, should be attributed to category II soils in terms of seismic properties; clay soils with a consistency index of 0.25< IL£ 0.5 with porosity factor e< 0.9 for clays and loams and e < 0,7 для супесей - к грунтам III категории.

Notes. The seismicity of tunnel construction sites should be determined depending on the seismic properties of the soil in which the tunnel is laid.

2. Seismicity of sites for the construction of bridge supports and retaining walls with shallow foundations should be determined depending on the seismic properties of the soil located at the foundations.

3. The seismicity of sites for the construction of bridge supports with deep foundations, as a rule, should be determined depending on the seismic properties of the soil of the upper 10-meter layer, counting from the natural soil surface, and when cutting the soil - from the soil surface after cutting. In cases where the calculation of the structure takes into account the forces of inertia of the masses of the soil cut through by the foundation, the seismicity of the construction site is determined depending on the seismic properties of the soil located at the foundations.

4. The seismicity of embankment construction sites and pipes under embankments should be determined depending on the seismic properties of the soil of the upper 10-meter layer of the embankment base.

5. The seismicity of excavation construction sites may be determined depending on the seismic properties of the soil of a 10-meter layer, counting from the contour of the excavation slopes.

ROAD ROUTING

4.5. When tracing roads in areas with seismic activity of 7, 8 and 9 points, as a rule, it is necessary to bypass areas that are especially unfavorable in engineering and geological terms, in particular, zones of possible collapses, landslides and avalanches.

4.6. Tracing roads in areas with seismic activity of 8 and 9 points along non-rocky slopes with a slope steepness of more than 1: 1.5 is allowed only on the basis of the results of special engineering and geological surveys. Tracing roads along non-rocky slopes with a steepness of 1: 1 or more is not allowed.

GROUND PATH AND SURFACE STRUCTURE

4.7. With an estimated seismicity of 9 points and a height of embankments (depth of excavations) of more than 4 m, the slopes of the subgrade from non-rocky soils should be taken at 1: 0.25 the position of the slopes designed for non-seismic areas. Slopes with a steepness of 1:2.25 or less are allowed to be designed according to the standards for non-seismic areas.

Slopes of cuts and half-cuts located in rocky soils, as well as slopes of embankments made of coarse-grained soils containing less than 20% by weight of aggregate, are allowed to be designed according to the standards for non-seismic areas.

Increased requirements should be imposed on the quality of the used wall stone materials and mortar. Stone, brick or block surfaces must be free of dust before laying. Portland cement should be used as a binder in masonry mortars.

Before the start of stone work the construction laboratory determines the optimal ratio between the value of pre-moistening of the local wall stone material and the water content of the mortar mixture. Solutions are used with high water-retaining capacity (water separation is not more than 2%). The use of cement mortars without plasticizers is not allowed.

Brickwork and ceramic slotted stones comply with the following additional requirements: masonry of stone structures is erected for the entire thickness of the structures in each row; horizontal, vertical, transverse and longitudinal joints of the masonry are completely filled with mortar with trimming of the mortar on the outer sides of the masonry; masonry walls in places of mutual adjacency are erected simultaneously; bonded rows of masonry, including backfilling, are laid out from whole stone and brick; temporary (assembly) gaps in the masonry being erected end with an inclined shtraba and are located outside the places of constructive reinforcement of the walls.

When reinforcing brickwork(pillars) it is necessary to ensure that the thickness of the seams in which the reinforcement is located exceeds the diameter of the reinforcement by at least 4 mm, subject to the average thickness of the seam for this masonry. The diameter of the wire of transverse meshes for reinforcing masonry is allowed not less than 3 and not more than 8 mm. With a wire diameter of more than 5 mm, a zigzag mesh should be used. The use of individual rods (laid mutually perpendicular in adjacent seams) instead of bound or welded rectangular meshes or zigzag meshes is prohibited.

To control the placement of rebar when mesh reinforcement of pillars and piers, the ends of individual rods (at least two) in each mesh should be released from the horizontal joints of the masonry by 2-3 mm.

During the masonry process, the worker or foreman must ensure that the methods of fixing the girders, beams, decks and floor panels in the walls and on the pillars are consistent with the project. The ends of the split girders and beams resting on the internal walls and pillars must be connected and embedded in the masonry; according to the project, reinforced concrete or metal linings are laid under the ends of the runs and beams.

When laying ordinary or wedge-shaped jumpers only selected whole bricks should be used and mortar grade 25 and higher should be used. Lintels are embedded in the walls at a distance of at least 25 cm from the slope of the opening. Under the bottom row of bricks, stacked iron or steel wire with a diameter of 4–6 mm is placed in a layer of mortar at the rate of one rod with a cross section of 0.2 cm2 for each part of the lintel half a brick thick, unless the project provides for stronger reinforcement.

When laying the cornice the overhang of each row should not exceed 1/3 of the length of the brick, and the total extension of the cornice should not exceed half the thickness of the wall. Eaves with a large extension should be reinforced or run on reinforced concrete slabs, etc., reinforcing them with anchors embedded in the masonry.

Brickwork walls must be carried out in accordance with the requirements SNiP 3.03.01-87. During the production of brickwork, acceptance is carried out according to the act of hidden work. Hidden works subject to acceptance include: completed waterproofing; installed fittings; masonry areas in the places where girders and beams are supported; the installation of embedded parts - ties, anchors, etc.; fixing cornices and balconies; corrosion protection of steel elements and parts embedded in masonry; sealing the ends of girders and beams in walls and pillars (presence of base plates, anchors and other necessary details); sedimentary seams; support of floor slabs on walls, etc.