What is Building Deformation Monitoring?
It is a systematic observation of the factors that determine the degree and rate of deformation of buildings.
Building deformation monitoring is performed continuously over a given period, which makes it possible to determine the dynamics of the deformation process at foundations, walls, columns, floors, stairs and elements of load-bearing rigid structures, to record changes in soil properties under the structure.
- assessment of the current state of the emergency facility,
- ensuring the safety of operation of buildings that fall into the impact zone of new construction, restoration or reconstruction
- determination of the speed and degree of change in the technical condition of the building.
You can conduct a study of the state of neighboring buildings under construction or monitor the dynamics of the opening of cracks in finished objects.
Why is it necessary to monitor building deformations?
Any construction work leads to an increase in the load on the foundations, violation of the integrity of the underground space, the organization of additional main communications - all this, to varying degrees, affects the technical parameters of the surrounding structures. By monitoring the deformations of buildings, developers get a complete picture of the condition of nearby buildings. They can control the current workflow to prevent unforeseen consequences of the work being carried out.
When might a monitoring service be required?
Professional monitoring of buildings during construction carried out when it is necessary to carry out a number of activities in a built-up area. This can be driving piles, tearing off a foundation pit or arranging communications, reconstruction of architectural historical monuments, as well as in the following cases:
- the end of the standard period of operation of the house,
- detecting defects during the maintenance of the building by the homeowner,
- changes in the purpose of the building,
- sale or purchase of real estate,
- determining the suitability of an object for use after a fire,
- identifying the consequences after natural disasters,
- regulations of the building supervision authorities.
Building settlement monitoring 
allows you to develop timely, adequate solutions to prevent the impact of negative factors on neighboring structures during construction, to guarantee residents and homeowners the safety of repair or construction works.
Long-term monitoring of possible building precipitation in the construction area allows:
- establish the degree and rate of deformation (settlement) of the building,
- control the bends, deflections or rolls of the building.
These observations are especially relevant in the development of foundation pits and pile driving; they are carried out in accordance with GOST 31937-2011.
Stages of the survey of neighboring buildings under construction
Technical monitoring algorithm:
- General analysis of project documents.
- Preparatory work.
- Visual inspection of the structure.
- Preliminary assessment of the upcoming scope of work.
- Installation activities.
- Instrumental inspection of the building (identification of the carbonization depth of concrete slabs, determination of the state of reinforcement, load-bearing beams, and other structural elements).
At the end of the research work, specialists draw up defect maps, detailed tables, drawings of verification calculations, reflecting the real state of the structure.
Documents received after monitoring
The experts reflect the result of monitoring the deformations of buildings in the expert and technical opinion. This is a package of documents:
- dimensional drawings,
- defect and autopsy cards,
- photo report with a detailed description of the pictures,
- test tables,
- conclusion with the assignment of the category of the identified technical condition to the object under study, corresponding to the standards of GOST and SP 13-102-2003,
- calculations of physical, obsolescence of the structure as a whole,
- a list of recommended measures to eliminate detected defects, recommendations for further operation.
The conclusion is signed by experts performing tests, heads of departments, company management.
What permissions should a company have?
For the legitimate monitoring of building deformations, the company's specialists must have permission to the relevant work. The company itself is a permitting certificate for the implementation of works affecting the safety of commercial, residential real estate.
How much does it cost to monitor a building and structure?
The cost of organizing monitoring work is determined by a number of parameters: the complexity of the technical task, the scale of work, the amount of tasks assigned to the experts.
Taking into account the presence of various conditions, the cost of the study is calculated by specialists individually for a specific case.
What is the benefit of monitoring existing fractures?
Within the framework of a full-fledged survey of buildings, a critical stage is monitoring of building cracks - determining the causes of their formation, the dynamics of development. Every crack poses a serious threat. Since routine inspection rarely helps to establish the degree of hazard, professional observation of the development of cracks in finished structures is necessary.
The process of monitoring the development of crevices involves the installation of beacons on the walls of the building, which help control the flow of deformations in structures, prevent collapses or accidents. When monitoring the opening of cracks, the installation of beacons on the building makes it possible to clearly record the changes taking place. These can be electronic, plaster, plastic or point beacons.
The survey results allow homeowners to develop, take measures for the further operation of structures, determine the type of repair measures to eliminate the development of cracks. Laboratory construction expertise"A-Expert" offers legitimate, competent services for the implementation of construction monitoring in Moscow, St. Petersburg and other regions of Russia. We have a staff of experienced, certified specialists, an advanced technical base for monitoring work at the level of world standards.
A building cannot always be strong and reliable. It weakens over time, its structures and elements are deformed. The situation is even more serious when capital work is being carried out nearby. This is either new construction or serious earthworks. Buildings stand on foundations and foundations stand on the ground. That is, the earth is also a foundation. The building presses on the ground, it rests on the ground. This creates vertical and horizontal forces acting on the ground. And, if you start to dig a pit near the building, then micro shifts occur in the ground in the area of the pit and the density of the ground that is under the building begins to decrease because of this. If this process is not monitored and fixing, strengthening measures are not taken, then the building can deform, tilt (Leaning Tower of Pisa) and even collapse. To prevent this from happening, order monitoring.
Attention
The losing party will reimburse you for the examination.
- long-term monitoring of the precipitation of one or more buildings using a complex of surveys, geodetic surveys, engineering survey, geological methods during construction in cramped urban conditions.
Company "CA Design and Engineering Center" He has significant experience and carries out work on the monitoring of buildings and structures.
Target: to determine the degree and rate of deformation (settlement) of buildings, as well as control over bends, deflections and heel of a building or a number of buildings falling into the zone of new construction.
Most often, monitoring is carried out when cutting excavations, driving piles or laying communications in the area of existing buildings.
In addition, reconstruction of historical architectural monuments is taking place, and already built houses require an examination to assess their condition and suitability for further use (for example, in preparation for sale). We inspect all facades for cracks on rented aerial platforms. All this requires a certain set of studies using appropriate techniques and equipment - monitoring. Moreover, only highly qualified specialists with a license to conduct such research have admission to such work. The company CPI CA has a staff of just such employees. She will help you quickly and efficiently solve problems by monitoring your property.
What is building monitoring
Monitoring of buildings and structures is the control over the functioning of various systems: the reliability of the entire structure, the engineering network and its individual nodes, control over the state of the soil massif, etc. All this includes engineering research, geodetic measurements, engineering and geological surveys, measurement of possible deformations and a whole range of necessary measurements.
Results of soil testing by the method of compressor compression 1 |
Stamping plan |
The results of soil testing by the method of compressor compression 2 |
When and how often?
According to the current regulatory framework, each building and structure is subject to inspection two years after commissioning. In the future, it is carried out after certain periods of time:
- For structures operating in an unfavorable environment (aggressive environments, vibration and seismic loads, high humidity, etc.), the check is carried out every 5 years.
- For a typical environment - once every 10 years.
- For historical buildings and monuments - constant observation mode.
- After the end of the standard operating life of the facility.
- In the event of significant defects and damage during the maintenance of the structure by the owner.
- Changing the purpose of the building. Before conversion, studies are carried out to prove its suitability for use for new functions.
- When selling and buying real estate. Before the sale, the owner is obliged to provide a document confirming the suitability of the facility for further use.
- To determine the suitability of a structure for operation after a fire. The modulus of elasticity and yield strength of concrete, the main building material today, deteriorate significantly after exposure to high temperatures and subsequent cooling with a jet of water from fire hydrants.
- In the event that occurred natural Disasters(earthquakes with a magnitude of 7 points on the Richter scale, etc.) and accidents that led to the destruction of the object.
- By order of the state construction supervision authorities.
Monitoring stages
The stages of such operations by our specialists have a clear sequence:
- Analysis of the documentation provided by the client: project, as-built documentation, results of previous studies, etc.
- Visual inspection of the facility and preliminary assessment of the scope of work.
- Cleaning of building facades from efflorescence and hydrophobization.
- Inspection of building structures using special tools - instrumental inspection of buildings. Various works are carried out to determine the state of the bearing beams, the depth of concrete carbonization, the state of the reinforcement, etc.
- If necessary, measurements include destructive methods: pit passage, control openings, etc.
- After the research carried out, precise drawings, defect maps and tables of verification calculations are drawn up.
Monitoring results for the customer
The results of the studies carried out are reflected in the technical conclusion, which is a package of documents:
- The very technical conclusion with the designation of dimensions and a description of all building structures (foundation, walls, roof, floor, slabs, beams, etc.)
- Accurate dimensional drawings with reference to all supporting structures.
- Defect maps. When examining already commissioned houses and buildings.
- Autopsy map made for monitoring. Places of openings of structures are applied on it to analyze their condition, as well as places of pits made with reference to a geodetic grid.
- Photo report with pictures and a detailed description of each picture.
- Test tables and processing of their results.
- Technical conclusion on the state of the object with the assignment of the category of technical condition in accordance with GOST R 53778-2010 and SP 13-102-2003.
- Calculation of the moral and physical deterioration of buildings and structures in operation.
- List of necessary work to eliminate the identified defects and carry out repairs, recommendations for further operation.
The conclusion on the results of the work performed is signed by the experts themselves who conducted the tests. Then it is approved by their immediate heads of departments and company management. The conclusion serves as the basis for assignments for the design of further work to strengthen the structures of the surveyed object, if necessary. In the event of significant damage to the building structures, the customer is immediately informed, and information is sent to the state construction supervision authorities. All research results are entered in the passport of the surveyed building.
Monitoring of buildings and structures is one of the activities of the CPI SA company. Highly qualified specialists, having extensive experience in carrying out work in this area, will conduct surveys in the shortest possible time, but absolutely without losing the quality of work.
Order monitoring of buildings and structures in the Design and Engineering Center company.
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The concept of monitoring the technical condition of buildings and structures was introduced into the system of normative documentation with the entry into force (Buildings and structures. Rules for inspection and monitoring of technical condition). Earlier we already. Now let's dwell on what monitoring is and how it is regulated by this GOST.There are four main types of monitoring:
- general monitoring of the technical condition of buildings and structures
- monitoring of the technical condition of buildings and structures falling into the zone of influence of construction projects and natural and man-made impacts
- monitoring the technical condition of buildings and structures that are in limited serviceable or emergency condition
- monitoring the technical condition of unique buildings and structures
Monitoring of unique buildings and structures is mandatory. Systems for such monitoring should be developed at the design stage and installed during construction to ensure continuous monitoring of the state of structures. For this type of monitoring, complex automatic stationary systems are used, developed individually for each building.
In the process of designing the construction of new and reconstruction of existing buildings, the zone of influence of this construction on buildings and structures located near the construction site is determined. For such buildings, the project should provide for another type of monitoring - monitoring the technical condition of buildings and structures that fall into the zone of influence of construction projects and natural and man-made impacts. Monitoring activities are developed within the framework of the PIC based on the results of the survey of buildings and engineering and geological surveys. For monitoring, they mainly use geodetic methods, as well as visual observations and measurement of the dynamic parameters of buildings.
General monitoring of the technical condition of buildings and structures carried out to identify significant changes in their stress-strain state (obvious deterioration of the technical condition). For this type of monitoring, measurement of the dynamic parameters of the building and visual inspection are used. Due to the low labor intensity of these works, such monitoring can be effectively used to monitor the state of a group of buildings. It is recommended to conduct it once every two years.
Monitoring of the technical condition of buildings and structures that are in limited serviceable or emergency condition. In the event of an emergency state of structures, the operation of the building is not allowed, and monitoring of them must be established without fail for the entire period until the completion of work on bringing the structures into a working condition. With this type of monitoring, a complex of observations and measurements is used that is most suitable for monitoring changes in the state of structures. The dynamic parameters of the building must be determined. In case of a limited working condition of structures, the operation of the building is possible either with constant monitoring of them, or with the restoration / reinforcement of structures. After the completion of the repair work, the reconstructed / reinforced structures can be monitored (monitored). If necessary, monitoring can be carried out for structures that are in working condition.
It is necessary to distinguish between the above types of monitoring of the technical condition of buildings and structures, since each type of monitoring has its own specific goals and methods (tools) to achieve them. The selection of monitoring techniques and tools should be based on specific tasks, taking into account the state and characteristics of the facility. Monitoring the condition of buildings can significantly improve the safety of their operation. Modern monitoring tools, in comparison with the previously widespread ones, can significantly reduce the cost of monitoring while improving the quality, reliability and efficiency of control measures.
Impacts
The objectives of monitoring the technical condition of buildings (structures) falling into the zone of influence of new construction and natural and man-made impacts are implemented on the basis of:
Determination of absolute and relative values of deformations of structures of buildings (structures) and their comparison with calculated and permissible values;
Revealing the causes of occurrence and the degree of danger of deformations for the normal operation of facilities;
Taking timely measures to combat emerging deformations or to eliminate their consequences;
Refinement of design data and physical and mechanical characteristics of soils;
Clarification of design schemes for various types of buildings (structures) and communications;
Establishing the effectiveness of preventive and protective measures taken;
Clarification of the regularities of the process of displacement of soil rocks and the dependence of its parameters on the main influencing factors.
Monitoring of the technical condition of buildings (structures) falling into the zone of influence of new construction and natural-man-made impacts is planned before the start of construction or the expected natural-man-made impact.
Scientific and technical support and monitoring of new construction or reconstruction of facilities is allowed in accordance with MRDS 02-2008.
When monitoring the technical condition of buildings (structures) that fall into the zone of influence of new construction or reconstruction of objects arranged by an open method, data (radius of the zone of influence, additional deformations, etc.) are used in accordance with MGSN 2.07-2001.
The assessment of the zone of influence of dynamic influences on the surrounding buildings and structures during the immersion of pile elements of buildings under construction is carried out in accordance with SNiP 3.02.01-87.
The outer boundaries of the trough of displacement on the earth's surface with the underground method of erecting an object are determined by the boundary angles, and the outer boundaries of its dangerous part - by the angles of displacement. The values of these angles depend on the properties of the rocks and are determined empirically. In the absence of experimental data, the values of the boundary angles and displacement angles are determined in accordance with Appendix P GOST 31937-2011. The angles of the discontinuities are taken 10 ° more than the angles of displacement.
The determination of the values of the expected maximum displacements and deformations of the earth's surface and the expected displacements and deformations at the points of the displacement trough during the underground method of building an object is carried out in accordance with Appendix R GOST 31937-2011.
The total duration of the process of displacement of the earth's surface over the produced underground workings and the period of dangerous deformations are determined in accordance with Appendix C of GOST 31937-2011.
When monitoring the technical condition of buildings (structures) that fall into the zone of influence of construction or reconstruction of objects with the underground method of their construction, geodetic and mine surveying work is carried out, which are carried out during the entire production cycle of the construction of the object until the deformation process of both the object itself and the mass of soil is attenuated. rocks in accordance with the design documentation agreed in the established manner.
The compilation of the observation program should be preceded by an assessment and forecast of the geomechanical state of the rock mass in the area of large-scale construction and the zone of its influence on objects located on the earth's surface.
The assessment of the geomechanical state before the start of construction work is carried out on the basis of geological data and engineering surveys... At the same time, special attention is paid to the determination of the natural stress field, the characteristics of tectonic disturbances, fracturing, layering, water abundance, karst formation and other features of the massif.
The forecast of changes in the geomechanical state of the rock mass under the influence of mining operations is carried out both for standard conditions construction and operation of the facility, as well as for emergency situations (destruction of the lining of foundation pits, breakthrough of quicksands in them, development of karst formations, activation of ancient landslides, etc.). The forecast consists of determining the expected parameters of the development of geomechanical processes, the main of which are:
Sizes and locations of displacement zones;
The values of the maximum displacements and deformations;
The nature of the distribution of deformations in the displacement trough;
The total duration of the displacement process and the period of dangerous deformations.
Instrumental observations of the displacement of the earth's surface and the objects located on it are carried out in order to obtain information about the change in the geomechanical state of the rock mass, on the basis of which the necessary preventive and protective measures can be taken in a timely manner.
Instrumental observations of the displacement of the earth's surface and structures are carried out using a system of benchmarks laid in the ground and structures of buildings and structures, and for the movement of a rock mass - using deep benchmarks laid in wells. In built-up areas, in order to exclude the possibility of damage to underground utilities, the places for laying benchmarks must be agreed with the local executive authorities. The laying of benchmarks and initial observations on them should be carried out before the start of construction. The procedure for breaking down the observation network of benchmarks is presented in Appendix T GOST 31937-2011.
Simultaneously with the breakdown of the observational network of benchmarks, places should be outlined for laying three initial benchmarks, with the help of which the position of the reference benchmarks of the profile line in height will be determined in the future and their immobility will be monitored.
To observe individual buildings (structures) falling into the zone of influence of new construction and natural-man-made impacts, wall and ground benchmarks are laid. Before the start of observations, the technical condition of buildings (structures) is examined, dynamic parameters are measured, and passports are drawn up.
Observations of the displacement of the earth's surface, as well as the deformations of buildings and structures falling into the zone of influence of construction underground structure, consist in the periodic instrumental determination of the position of the benchmarks with the fixation of visible violations, as well as all factors affecting the values and nature of displacements and deformations. For buildings (structures), measurements of their dynamic parameters are also carried out.
Observations of the deformations of the foundations of buildings (structures) are carried out in accordance with GOST 24846. When observing buildings, the uneven subsidence of the foundations is determined, cracks and other damage to structures, the reliability of their support units, the presence of the necessary gaps in the seams and hinged supports are recorded. For industrial buildings also determine the relative horizontal displacements of the separately standing foundations of the columns, the rolls of the foundations of technological equipment, and in the presence of bridge cranes - deviations from the design position of the crane runways: transverse and longitudinal slopes, changes in track width and the approach of the crane to buildings.
Determination of the measurement accuracy of vertical and horizontal deformations is carried out depending on the expected calculated value of the displacement. In the absence of data on the calculated values of deformations of foundations and foundations, it is allowed to establish an accuracy class for measuring vertical and horizontal displacements:
I - for buildings (structures): unique, in operation for more than 50 years, erected on rocky and semi-rocky soils;
II - for buildings (structures) erected on sandy, clayey and other compressible soils;
III - for buildings (structures) erected on bulk, subsidence, peat and other highly compressed soils;
IV - for earth structures.
Limit errors in measuring the roll, depending on the height H of the building (structure) should not exceed the following values, mm:
For civil buildings (structures) - 0.0001H;
For industrial buildings (structures) - 0.0005H;
For foundations for machines and units - 0.00001Н.
Geodetic methods and instruments are used to measure vertical and horizontal displacements of the earth's surface and, if necessary, the bottom of the excavation. When cracks appear on the earth's surface within the slope zone, additional systematic observations of their development along the length, width and depth are organized.
Simultaneously with instrumental observations on the earth's surface, surveying observations are carried out directly in the underground structure.
Based on the materials of measurements, calculations and geological surveying documentation, a conclusion is drawn up containing the necessary information about the state of buildings and structures falling into the zone of influence of large new construction and natural-man-made impacts, changes in the geomechanical state of the rock mass; the degree of danger and the rate of development of negative processes (if necessary). The conclusion is accompanied by documentation confirming the conclusions drawn in it.
The form of a conclusion on the technical condition of an object falling into the zone of influence of new construction and natural and man-made impacts is presented in Appendix U GOST 31937-2011.
Appendix U
(required)
Form of conclusion (current) on monitoring the technical condition of buildings (structures) falling into the zone of influence of new construction and
natural and man-made impacts
It is compiled by the head organization based on the results of the stage of monitoring the technical condition of buildings (structures) falling into the zone of influence of new construction and natural and man-made impacts.
| Conclusion on the stage of monitoring the technical condition of objects falling into the zone of influence of new construction and natural and man-made impacts | |
| 1 Information defining the location and type of impact (epicenter of natural and technogenic impact, address of the construction site) | |
| 2 Monitoring stage number | |
| 4 Radius of the zone of influence | |
| 5 List of objects falling into the impact zone | |
| 6 Lead organization of the monitoring phase | |
| 7 List of organizations that carried out the stage of monitoring the technical condition of facilities, indicating which facility was surveyed and which organization | |
| 8 List of objects, the category of technical condition of which corresponds to a limited working condition | |
| 9 The list of objects, the category of technical state of which corresponds to the emergency state | |
| 10 General assessment of the situation | |
| 11 Information requiring urgent solutions to emerging safety problems |
Appendices - Conclusions on the stage of monitoring the technical state of each object that is in a limited operational or emergency state (see Appendix H).
Conclusions on the stage of monitoring the technical state of each object that is not in a limited operational or emergency state (see Appendix L).
Combined plan of the observation system of benchmarks and the underground structure.
Vertical geological sections along profile lines.
Records of the displacements of benchmarks in the vertical and horizontal planes in the direction of the profile line.
Sheets of the rates of displacement of the benchmarks.
Records of the settlement of benchmarks and the measured lengths of the intervals between them.
Calculation results for each of the land subsidence benchmarks for all calculated intervals between benchmarks:
Slopes, curvatures, radii of curvature, horizontal deformations;
Typical points of the trough of displacement relative to the boundaries of the underground structure (boundaries of the zone of influence, points with maximum stretching and compression, points with maximum slopes, points with maximum curvature;
Areas of the earth's surface on which concentrated deformations have formed in the form of cracks, steps and ledges).
General Provisions
Geotechnical monitoring is a set of works based on field observations of the behavior of structures of a newly erected or reconstructed structure, its foundation, including the soil mass surrounding (containing) the structure, and structures of structures of the surrounding buildings.
The purpose of geotechnical monitoring is to ensure the safety of construction and the operational reliability of new construction or reconstruction facilities and structures of surrounding buildings by timely detection of changes in the controlled parameters of structures and soils of foundations, which can lead to a transition of facilities to a limited working or emergency state.
The tasks to be solved during geotechnical monitoring are determined by SP22.13330.2011 (clause 12.2).
Objects of new construction and reconstruction subject to geotechnical monitoring are established by SP 22.13330.2011 (clause 12.4) depending on the uniqueness of the object, the level of responsibility of the structures, the category of complexity of the geotechnical conditions and the depth of the pit. The uniqueness of the object and the level of responsibility of the structure are established in accordance with Federal law of December 30, 2009 N384-FZ "Technical regulations on the safety of buildings and structures", the Urban Planning Code of the Russian Federation of December 29, 2004 N190-FZ and the instructions of GOST 27751.
Structures of the surrounding buildings of the levels of responsibility KS-3 (increased) and KS-2 (normal), incl. underground engineering communications are subject to geotechnical monitoring when they are located in the zone of influence of new construction or reconstruction, the dimensions of which are determined based on the results of a geotechnical forecast. In the absence of the results of the geotechnical forecast of the impact of the structure under construction, the objects of geotechnical monitoring of the surrounding buildings are assigned according to the preliminary zone of influence determined in accordance with the instructions of SP22.13330.2011 (paragraph 9.36).
Geotechnical monitoring of new construction and reconstruction facilities, as well as construction of surrounding buildings, incl. underground utilities are carried out in accordance with the program, which is developed and approved as part of the project documentation.
For structures of the level of responsibility KS-3 (increased) with III category of engineering and geological conditions or on a special assignment in other cases, on the basis of the program, a project of geotechnical monitoring (observation station) is developed.
An observation station for geotechnical monitoring during the construction period should provide the possibility of its subsequent inclusion in a structured monitoring and control system engineering systems facilities (SMIS) if a monitoring system is provided for the facility during operation. In this case, the instruments and equipment used are recommended to be selected based on the conditions for ensuring the design life of the monitoring system during the operation period, the required accuracy and resistance to external influences, the possibility of remote reading
The development of the program and project of geotechnical monitoring, as well as its implementation, is carried out by specialized organizations, the main activity of which is the implementation of complex engineering surveys and the design of foundations, foundations and underground parts of structures, which have qualified and experienced personnel, appropriate certified equipment and software.
Building structures
The systems for monitoring the stress-strain state of building structures considered above are developed on the basis of various sensors: strain gauges, fiber-optic, piezoelectric and string. Therefore, in order to select a monitoring system, it is necessary to analyze the sensors on the basis of which it is built.
CJSC "Triada-Holding"
String voltage sensor.
A string voltage sensor is used to measure voltages. Consists of a coil and string element with metal rods outlets at both ends. The sensors are welded to the reinforcement cage or attached to the surface of a metal structure. The sensors are distinguished by increased strength, reliability and tightness. Data from sensors can be read both individually and as part of a data collection system.
Advantages: robust, reliable, easy to operate, suitable for use when reading and accumulating data in a remote mode, sealed (waterproof), individually calibrated, long cable length does not affect signal stability, does not react to bending, built-in thermistor.
Rice. 1.12 General view of the voltage sensor.
Casting string strain gauge.
Soil Instruments' cast-in string strain gauges are designed to measure deformations in reinforced concrete structures. The measuring sensor of the sensor consists of a string element attached to special flanges at the ends of the sensor body and a secondary transducer in the form of an electromagnetic coil.
The sensor body is made of stainless steel. The measuring base is 150 mm. Before the concrete is poured, the sensor can be attached to the reinforcement with a conventional tying wire or a 2-, 3- or 4-way rosette can be created, thus providing the ability to measure deformations in multiple directions. In addition, the sensor can be embedded in a concrete block for subsequent embedding of the entire block (with the sensor installed inside) into a new structure or into pre-cut holes in an existing structure. After embedding the sensor, a block with an electromagnetic coil, mounted on the sensor body, fixes any deformations in the structure.
Sensors can be polled individually or automatically remotely (if they are part of a data collection system).
The cables from the sensors are laid to the reading device or measuring point, and they, like the sensor, must be protected from damage during the pouring of concrete.
Rice. 1.13 Casting string strain gauge.
Wireless tilt sensor for measuring relative displacements of a structure.
Electrical levels are fluid sensors with no moving parts. They are powered by a bridge or half-bridge circuit, and their output power depends on the magnitude and direction of the sensor deflection. A rectifier and a digital radio receiver are built into the sensor. The range of the receiver is up to 1000 m (depending on model and installation conditions). A signal coding system is used to transmit data in digital format.
The sensor is compact in size. The sensor should be installed so that it is not subject to temperature influences, and also so that during installation and during operation it is possible to zero it.
The design of the sensor assumes installation directly on the surface of the structure. The sensor consumes very little power and does not generate electromagnetic interference.
Advantages of the device: wireless communication between the sensor and the data accumulator, a service life of 10 years (when reading data every hour), data transmission in digital format ensures high quality and safety of work, the ability to build a complete profile of vertical displacements, the ability to automate work using software " I-Site ".
Rice. 1.14 Wireless tilt sensor.
String load cell.
The string load cell consists of a steel cylindrical body with built-in string sensors (up to 6 pieces) for measuring the compression of the cylinder under load. A sturdy PVC braided multicore cable is used to connect the sensor to the reader via the terminal. Alternatively, it is possible to connect sensors directly to the reader. To distribute the load and compensate for inaccuracies in alignment, a base plate is placed under the sensor during installation. Another base plate is positioned between the sensor and the anchor or bolt tensioner. To ensure reliable results, the slab is cast in such a way that its top edge is flat and perpendicular to the bolt or cable.
A terminal is required to connect each sensor element of the sensor. (Readings are averaged by the reader and the value is displayed in engineering units).
Rice. 1.15 String load cell.
String ground pressure sensor.
String soil pressure sensors are designed to measure pressure in soil massifs or bulk structures. The round flat element consists of two stainless steel plates welded around the periphery, the narrow gap between which is filled with hydraulic oil; the string transducer is connected to the flat element by a short steel tube to form a closed hydraulic system.
The sensor (element and transducer) is installed in the monitored environment and an armored cable connects it to a terminal, portable reader, or data storage device. The accuracy of the readings is independent of the cable length.
Rice. 1.16 String soil pressure sensor.
Crack sensor BCD-5B.
The Crack Sensor is designed to measure cracks that appear in concrete structures and rocky foundations in mines and quarries. Conventional crack sensors have a high measuring force and cannot provide high measurement accuracy if they are not rigidly fixed. Moreover, they are difficult to install on soft rocky ground. Compared to these, the BCD-5B has an extremely low measured force for accurate measurements and is easy to install even on weak rocky ground.
Fiber optic strain gauge (SVOD).
Fiber optic sensors can be used in situations in which electronic devices either cannot be used at all, or such use is accompanied by significant difficulties and costs.
The specialists of NPK "Monitoring-Center" are carrying out intensive work on the creation of construction monitoring systems based on fiber-optic measuring systems. Today NPK Monitoring-Center offers strain and temperature sensors that can be used in a wide class of tasks to ensure control of the building safety level.
Technical characteristics of the complex for measuring deformations based on SVOD
The basic sensor used in the monitoring system is a fiber-optic strain sensor. The sensor has several versions, allowing it to be poured into a reinforced concrete structure or mounted on the surface of building elements. The installation of sensors at the points of a potential source of destruction (heavy loads, moments) is regulated at the project stage. Control can be carried out both during installation and during operation of the structure. The electronic signal processing unit receives continuous information about the state of the structure at internal and external control points. Comparison of this information with design data on a continuous basis allows conclusions to be drawn about the "health" of the structure.
Fiber Optic Sensor Signal Meter (ISVOD)
Specifications.
The electronic signal transmission and processing unit (ISVOD) used in the monitoring system has a unified structure. Signal transmission can be carried out both through fiber-optic communication channels and through existing electrical networks (which does not require additional work on the equipment of communication channels), as well as in a wireless format.
Application of fiber-optic sensors of JSC "Monitoring-Center" in building structures and structures.
Output:
The sensors on the basis of which the monitoring systems are built have a number of advantages and disadvantages.
Load cells. Advantages: small size and weight; low inertia, which allows the use of strain gauges both for static and dynamic measurements; have a linear characteristic; allow to carry out measurements remotely and at many points; the way of their installation on the investigated part does not require complex devices and does not distort the deformation field of the investigated part.
The main disadvantages of strain gauges are temperature sensitivity, which in the conditions of the far north negates all the advantages of strain gages, and a small output signal, which is difficult to measure with high accuracy.
String pickups. Advantages: stable output signal frequency, insensitivity to long cable lengths, less environmental sensitivity compared to strain gauges.
The main disadvantage of single-string sensors is a sharply non-linear static characteristic. Differential string transducers have much less static nonlinearity. The conversion accuracy of string pickups increases if the main component of the rigidity of the mechanical system is the rigidity of the string.
The most suitable type of sensors for use in the Far North and aggressive environment are fiber optic sensors. With a number of advantages:
Immunity to electromagnetic interference;
Resistance to environmental influences;
Solid structure allows to withstand limit levels vibration and shock loads;
High sensitivity and broadband allow measuring and transmitting information over a considerable distance;
No mutual interference;
Explosion safety (guaranteed by the absolute inability of the fiber to be a prerequisite for a spark);
High corrosion resistance, especially to chemical solvents, oils, water;
Virtually no flaws.
The most suitable sensors for monitoring the stress-strain state of building structures are fiber-optic sensors, despite their price (from 45 to 65 thousand rubles), they are best suited for work in aggressive conditions, as well as in the Far North (work at temperatures up to -60 ° C). It is also important that the maximum distance of the sensor from the station is 1000 meters without deterioration of the transmitted signal, which is an unattainable result for sensors of another type.
Examples of design and operation of systems for monitoring structures and foundations of buildings and structures.
TOPIC 3. GENERAL MONITORING OF THE TECHNICAL CONDITION OF BUILDINGS AND STRUCTURES. MONITORING THE TECHNICAL CONDITION OF BUILDINGS AND FACILITIES IN A RESTRICTED OPERATING OR EMERGENCY CONDITION. MONITORING OF THE TECHNICAL CONDITION OF BUILDINGS AND STRUCTURES AFFECTING THE AREA OF INFLUENCE OF NEW CONSTRUCTION, RECONSTRUCTION AND NATURAL-TECHNOGENIC IMPACT. MONITORING OF TECHNICAL CONDITION OF UNIQUE BUILDINGS AND STRUCTURES.
General monitoring of the technical condition of buildings and structures
General monitoring of the technical condition of buildings and structures is a monitoring and control system carried out according to a specific program approved by the customer to identify objects on which significant changes in the stress-strain state of load-bearing structures or tilt have occurred, and for which an examination of their technical condition is required (changes stress-strain states are characterized by a change in existing and the emergence of new deformations or determined by instrumental measurements).
General monitoring of the technical condition of buildings and structures is carried out to identify objects, the change in the stress-strain state of which requires an examination of their technical condition.
In general monitoring, as a rule, they do not conduct a full inspection of the technical condition of buildings and structures, but conduct a visual inspection of structures in order to approximate the category of technical condition, measure the dynamic parameters of specific buildings and structures (see Appendix L GOST 31937-2011) and make up a passport of a building or structure (see Appendix M GOST 31937-2011).
If, according to the results of an approximate assessment, the category of the technical condition of a building or structure corresponds to the standard or operable technical condition, then repeated measurements of the dynamic parameters are carried out after two years.
If, according to the results of repeated measurements of the dynamic parameters, their changes do not exceed 10%, then the next measurements are carried out after another two years.
If, according to the results of an approximate assessment, the category of the technical state of a building or structure corresponds to a limited operational or emergency state, or if, when re-measuring the dynamic parameters of a building or structure, the measurement results differ by more than 10%, then the technical condition of such a building or structure is subject to mandatory unscheduled inspection.
Based on the results of the general monitoring of the technical condition of buildings and structures, the contractor draws up an opinion (see Appendix K GOST 31937-2011) on the stage of general monitoring of the technical condition of buildings and structures and an opinion on the technical condition of each building and structure, for which general monitoring of the technical condition was carried out (see Appendix L GOST 31937-2011).
Appendix K
(required)
Form of conclusion (current) on the stage of general monitoring
technical condition of buildings (structures)
The conclusion is drawn up by the head organization based on the results of the stage of general monitoring of the technical condition of buildings (structures).
| Conclusion on the stage of general monitoring of the technical condition of buildings (structures) | |
| 1 List of object addresses | |
| 2 Monitoring stage number | |
| 3 Time of the monitoring stage | |
| 4 Lead organization of the monitoring phase | |
| 5 List of organizations that carried out the stage of monitoring the technical condition of facilities, indicating which facility was surveyed and which organization | |
| 6 The list of objects, the category of technical condition of which corresponds to a limited working condition | |
| 7 List of objects, the category of technical condition of which corresponds to the emergency state | |
| 8 General assessment of the situation | |
| 9 Information requiring urgent solutions to emerging safety problems |
Appendix - Conclusions on the monitoring of the technical condition of each facility during the general monitoring of the technical condition of buildings and structures of the city, see Appendix L.
Appendix L
(required)
Conclusion form (current) on the stage of monitoring the technical condition of the object
for general monitoring of buildings (structures)
| Conclusion on the stage of monitoring the technical condition of the facility during the general monitoring of the technical condition of buildings and structures | |
| 1 Object address | |
| 2 Monitoring stage number | |
| 3 Time of the monitoring stage | |
| 4 Organization that conducted the monitoring phase | |
| 5 Previous roll value of the object along the major axis | |
| 6 The current roll value of the object along the major axis | |
| 7 Previous roll value of the object along the minor axis | |
| 8 Current roll value of the object along the minor axis | |
| 9 Previous value of the period of the fundamental tone of natural oscillations along the major axis | |
| 10 Current value of the period of the fundamental tone of natural oscillations along the major axis | |
| 11 Previous value of the period of the fundamental tone of natural oscillations along the minor axis | |
| 12 Current value of the period of the fundamental tone of natural oscillations along the minor axis | |
| 13 Previous value of the period of the fundamental tone of natural oscillations along the vertical axis | |
| 14 Current value of the period of the fundamental tone of natural oscillations along the vertical axis | |
| 15 Previous value of the logarithmic decrement of the fundamental tone of natural oscillations along the major axis | |
| 16 Current value of the logarithmic decrement of the fundamental tone of natural oscillations along the major axis | |
| 17 Previous value of the logarithmic decrement of the main |
Where does monitoring begin?
Measures for monitoring the actual state of an architectural object and its ability for further use, in accordance with the provisions of technical standards and other documents, are carried out for buildings and structures commissioned.
Let's list the main goals of these activities.
- tracking any changes in the general condition of existing and operated buildings. This data allows you to develop adequate and timely solutions to counter any negative factors that can lead to an accident or destruction of the building;
- detection of elements and parts of the controlled object that have undergone influences, which have changed the state of the load-bearing parts of building structures. Here it is necessary to find out whether there has been a deformation of the parts or a redistribution of stresses. In this case, there is a need for expert examination of the object;
- guarantee of safe use of construction sites and their trouble-free operation. It is ensured due to the fact that regular inspections make it possible to timely identify potentially dangerous transformations of stresses or deformations in the details of the structure and soil segments, and take the necessary measures in time to prevent the state of the building being inspected from changing from operable to partially operable, or, even worse, to emergency. ;
- constant monitoring of any changes in the actual technical condition of each specific building, an objective assessment of the degree of changes occurring in it and their speed. Possession of such information allows you to quickly take the necessary measures to prevent a sharp deterioration in the state of the entire object.
Industry accepted procedures for the professional monitoring of the condition of construction sites serve one purpose - the identification of altered building structures. If their current state of distribution of tensions and the presence of deformations cause certain concerns among specialists, then an urgent and more thorough examination of the object will be required.
Monitoring of emergency construction sites, as well as buildings in a state of limited working capacity
During the current check of the current state of those used buildings that cannot be recognized as fully operational or are considered emergency, it is required to constantly monitor the natural processes occurring both in the supporting soils and directly in the structural elements of objects. These activities are carried out both before the start of any work aimed at reconstruction, restoration or strengthening of buildings, and on an ongoing basis in the process of repair activities.
Monitoring the actual situation with what is happening in the structures of the object and in the surrounding soil assumes that at each stage of the restoration work carried out in the building, the following measures are taken:
- determination of the dynamic indicators of the object at a given time and their comparison with the figures recorded at the previous stage of work;
- assessment of the degree of how in the course of work the state of damage to the structure and defects of its elements, which were recorded earlier, has changed, as well as fixation of newly discovered flaws;
- repeated measurements of all previously recorded changes, distortions, kinks, rolls, cracks, deformations, etc. and comparison of the obtained measurement data with similar indicators at the previous stage of work;
- a comprehensive analysis of the information obtained in the course of monitoring at this stage;
- formulation of an interim conclusion on the actual technical condition of the building at the moment.
Monitoring of the technical condition of construction objects located in the zone of new development, falling into the area of work on the reconstruction of buildings or in the sphere of influence of natural or man-made influences
The main tasks of monitoring the current state of buildings and structures that are in the zone of current construction or in the area where natural and man-made impacts are recorded can be formulated as follows:
- it is required to determine the absolute indicators of the current deformation of building structures, calculate their standard relative values and compare with standard tolerances and calculated values;
- it is necessary to establish the causes of the appearance of deformations and objectively assess the level of their potential threat to the normal functioning of facilities;
- it is necessary to find out the current characteristics of the physical and mechanical state of soils, and, taking them into account, to clarify the available calculation data;
- it is extremely important to take all the necessary steps both to resist the emergence of new deformations, and to effectively eliminate the consequences of existing damage;
- it is strongly recommended to check the design schemes for buildings, structures, structures and communication facilities of various types that fall into the impact zone;
- it is required to constantly record the degree of effectiveness of measures taken to protect buildings and prevent the deterioration of their condition;
- it is necessary to find out the patterns and vectors along which soil rocks move, and also to establish how the main parameters of this process depend on the main external and internal factors.
Checking the status of unique objects, buildings and structures
In order to ensure trouble-free use and safe functioning of unique architectural or urban planning objects, periodic or continuous technical monitoring of the current state of all elements of their structures is carried out.
The data obtained in the course of such control measurements is the basis that will determine the list of works that can be performed at these facilities. In the course of monitoring the technical condition of unique buildings, all physical and chemical processes that occur deep in the structures of these structures and in the adjacent soil are checked. This allows engineers at the earliest stage to detect any negative tendencies leading to unfavorable changes in the state of the architectural elements of the building, one or another of its supporting structures, fragments of the foundation of one size or another, etc.
Having such information and taking into account its changes in the operational environment, the engineer can easily predict what kind of situation can lead to the fact that the considered urban planning object loses the possibility of operational operation and changes its actual state to "emergency" or to a state of "limited readiness". The same information allows you to develop a plan of necessary measures for timely counteraction to any destructive processes recorded in the course of monitoring.