A comprehensive experimental method for obtaining maximum load of a load-bearing member

Abstract

The application discloses a comprehensive experimental method for obtaining maximum load of a load-bearing component and relates to the field of load-bearing component maximum load measurement. For a removable component: a cutting range is determined on a load-bearing component in a building to be demolished or a building to be reinforced and repaired, and a first strain and a second strain of the load-bearing component are measured during the cutting process; a loading test is conducted on the cut load-bearing component, and an acoustic emission signal is collected; a first load and a second load of the load-bearing component are determined according to the first strain and the second strain; a third load of the load-bearing component is determined according to the acoustic emission signal; if the errors between the first load, the second load and the third load are all within a preset range, the average value of the three loads can be taken as the maximum load of the load-bearing component. For a non-removable component: a loading test is conducted on a core sample of the load-bearing component by using a pressure testing machine, an acoustic emission signal is collected, and the maximum load of the load-bearing component is determined. The accuracy of the load-bearing component maximum load measurement is improved.

Description

Technical Field

[0001] This invention relates to the field of measuring the maximum load of load-bearing components, and in particular to a comprehensive experimental method for obtaining the maximum load of load-bearing components. Background Technology

[0002] Currently, China's urban population is growing rapidly, and land resources are becoming increasingly scarce. While tall buildings effectively alleviate land shortages, they also bring challenges related to resilience and disaster prevention and mitigation. For example, fires and gas explosions are common problems. It is reported that in recent years, China experiences as many as 40,000 fires annually, causing numerous casualties and property losses. Furthermore, numerous gas explosions have occurred in various parts of China in recent years, drawing significant public attention. After a fire or explosion, timely structural inspection and assessment are essential prerequisites for determining whether and how to repair the affected tall buildings. For frame (shear wall) structure buildings, the load-bearing components are reinforced concrete columns, reinforced concrete shear walls, and beams. These components experience a decrease in load-bearing capacity after being subjected to high temperatures and explosive loads. Objectively understanding the stress changes in these components is beneficial for subsequent damage assessment and repair work.

[0003] Meanwhile, with the accelerating pace of urbanization and the advancement of urban renewal activities in China, an increasing number of tall buildings and structures need to be demolished. Currently, controlled blasting demolition is gradually becoming the dominant method for demolishing and renovating urban buildings and structures. However, the increasing height of buildings to be demolished and the increasing complexity of the surrounding environment have brought many limitations to blasting demolition work. Most blasting targets are located in densely populated areas such as urban districts and residential areas, inevitably surrounded by other buildings and structures. Therefore, in order to achieve the expected blasting effect and reduce the impact of blasting demolition on surrounding buildings and structures, it is necessary to strictly control the direction of building collapse, the degree of fragmentation, and the harmful effects of blasting debris, blasting noise, and air shock waves. Therefore, understanding the internal forces, load distribution, and bearing capacity of the building's load-bearing components is a necessary prerequisite for the scientific design of blasting parameters and blasting schemes, and also a necessary prerequisite for achieving the expected blasting effect.

[0004] In conclusion, whether it's the reinforcement and repair of tall buildings or the demolition by explosives, it's essential to employ advanced scientific methods to obtain the initial stress state of load-bearing components during their service life. Currently, the initial stress state is primarily obtained through building structural design or numerical simulation software, the scientific validity and rationality of which are questionable. Therefore, this invention, based on the principle of initial stress release and the acoustic emission principle during concrete sample strength testing, proposes a comprehensive field testing method for measuring the maximum load of load-bearing components through strain gauge measurement, DIC observation, and acoustic emission testing of concrete samples. Summary of the Invention

[0005] The purpose of this invention is to provide a comprehensive experimental method for obtaining the maximum load of load-bearing components, thereby improving the accuracy of measuring the maximum load of load-bearing components.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A comprehensive experimental method for obtaining the maximum load of a load-bearing component, for removable components, includes:

[0008] Determine the cutting range on the first load-bearing component of the building to be demolished or reinforced; the first load-bearing component is a removable component;

[0009] The first load-bearing component is cut according to the cutting range, and the strain of the first load-bearing component is measured during the cutting process; the strain includes a first strain and a second strain; the first strain is obtained by measuring the strain of the first load-bearing component using a non-contact full-field strain measurement system; the second strain is obtained by measuring the strain of the first load-bearing component using a strain gauge.

[0010] A load test was conducted on the cut-off load-bearing component using a pressure testing machine, and the first acoustic emission signal of the cut-off load-bearing component was collected using a first acoustic emission sensor.

[0011] The first load on the first load-bearing component is determined based on the first strain, and the second load on the first load-bearing component is determined based on the second strain.

[0012] The third load on the first load-bearing component is determined based on the first acoustic emission signal;

[0013] Determine whether the errors between the first load and the second load, the errors between the first load and the load, and the errors between the second load and the third load are all within a preset range;

[0014] If so, the average value of the first load, the second load, and the third load shall be taken as the maximum load of the first load-bearing component;

[0015] If not, return to the step of "determine the cutting range on the first load-bearing component in the building to be demolished or reinforced and repaired" until the errors of the first load and the second load, the first load and the third load, and the second load and the third load are all within the preset range.

[0016] or

[0017] Core samples were obtained by taking core samples from the second load-bearing component of the building to be demolished or reinforced; the second load-bearing component is a non-removable component.

[0018] The core sample was subjected to a loading test using a pressure testing machine, and a second acoustic emission signal was collected using a second acoustic emission sensor.

[0019] The maximum load of the second load-bearing component is determined based on the second acoustic emission signal.

[0020] Optionally, a pressure testing machine is used to perform a loading test on the cut-off load-bearing component, and a first acoustic emission sensor is used to collect the first acoustic emission signal of the cut-off load-bearing component, specifically including:

[0021] The cut-off load-bearing components are processed to obtain standard test pieces; the standard test pieces are cylinders.

[0022] The standard specimen was subjected to a loading test using a pressure testing machine, and the first acoustic emission signal of the standard specimen was collected using a first acoustic emission sensor.

[0023] Optionally, determining the third load on the first load-bearing component based on the first acoustic emission signal specifically includes:

[0024] Using the Kessel effect, the third load on the first load-bearing component is determined based on the first acoustic emission signal.

[0025] Optionally, the loading test is stopped when the load reaches 80% of the ultimate bearing capacity of the standard specimen.

[0026] Optionally, the first strain of the strain gauge is acquired using a static strain gauge.

[0027] Optionally, before cutting the first load-bearing member according to the cutting range and measuring the strain of the first load-bearing member during the cutting process, the method further includes:

[0028] Speckle patterns are evenly distributed within the cutting range; the speckles are used to measure the strain of the first load-bearing component using a non-contact full-field strain measurement system.

[0029] The strain gauge is attached at the designated position on the first load-bearing component.

[0030] Optionally, the strain gauge is attached to a designated position on the first load-bearing component, specifically including:

[0031] The preset position is subjected to plaster removal and sanding to obtain the processed preset position;

[0032] The strain gauge is attached to the preset position after the treatment.

[0033] Optionally, core samples may be taken from the middle interior of the second load-bearing component, with a minimum of three core samples.

[0034] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] This invention provides a comprehensive experimental method for obtaining the maximum load of load-bearing components. For removable components, the load is measured using strain gauges, a non-contact full-field strain measurement system, and a combination of loading tests and acoustic emission technology. The measurement results are compared pairwise. When the errors are all within a preset range, it indicates that the measurement structure of the three methods is accurate and effective, and the average value can be taken as the maximum load of the load-bearing component. For non-removable components, the maximum load is obtained using a combination of loading tests and acoustic emission technology. This invention provides data support for the design of blasting parameters and blasting schemes to control demolition blasting, in order to achieve the expected blasting effect, or provides a basis for the design of cross-sectional dimensions and material selection for building repair and reinforcement, thus improving the accuracy of measuring the maximum load of load-bearing components. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The flowchart shows the application of the comprehensive experimental method for obtaining the maximum load of a load-bearing component according to the present invention.

[0038] Figure 2 A flowchart of the comprehensive experimental method for obtaining the maximum load of a load-bearing component provided by the present invention;

[0039] Figure 3 A schematic diagram of the strain gauges and speckle arrangement of the column;

[0040] Figure 4 This is a schematic diagram of the loading of a standard specimen.

[0041] Symbol explanation:

[0042] A1~A8 - Transverse strain gauges, B1~B8 - Longitudinal strain gauges, C - Speckle pattern, D - Static strain gauge, E - Camera observation point, 1 - Pressure head of pressure testing machine, 2 - Axial deformation sensor, 3 - Standard specimen, 4 - Circumferential deformation sensor, 5 - Acoustic emission sensor, 6 - Pressure testing machine base. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The purpose of this invention is to provide a comprehensive experimental method for obtaining the maximum load of load-bearing components, thereby improving the accuracy of measuring the maximum load of load-bearing components and enhancing the quality of repair and reinforcement work on damaged buildings (structures) in resilient urban construction or the collapse and damage effect on buildings to be demolished in urban renewal activities.

[0045] To address the problems in existing technologies, this invention provides a comprehensive method for obtaining the initial stress of load-bearing components of tall buildings (a comprehensive experimental method for obtaining the maximum load of load-bearing components) based on the principles of stress relief method for measuring initial stress and acoustic emission technology for measuring initial stress.

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] The non-contact three-dimensional full-field strain measurement system combines digital image correlation (DIC) technology with binocular stereo vision technology to achieve three-dimensional full-field strain measurement of the object's surface during deformation by tracking speckle images on the object's surface.

[0048] Currently, the XTDIC-CONST-HR non-contact three-dimensional full-field strain measurement system has been widely used in the measurement of material mechanical properties and is a strain and deformation measurement solution that has been widely recognized and praised in the industry.

[0049] The method of this invention varies depending on the specific circumstances, such as... Figure 1 As shown, for removable load-bearing components, stress is released by cutting the column. Strain data is collected and the entire process is recorded during cutting. After cutting, the separated parts are processed, and then a pressure testing machine and acoustic emission device are used to conduct loading tests, obtain acoustic emission signals, and analyze the experimental data to determine the maximum load the column will bear during its service life. For non-removable load-bearing components, core samples are first taken from the damaged components. Then, a loading test is conducted using a pressure testing machine and acoustic emission device to obtain acoustic emission signals. The Kaiser effect point is analyzed to obtain the maximum load the structure will bear during its service life and the crack development. At the same time, the core sample strength is obtained. Based on the core sample situation, a damage assessment is conducted, and a reinforcement and repair method or a removal plan is selected.

[0050] Example 1

[0051] like Figure 2 As shown, the comprehensive experimental method for obtaining the maximum load of a load-bearing component provided by this invention includes:

[0052] Step 201: Determine the cutting range on the first load-bearing component of the building to be demolished or reinforced. The first load-bearing component is a removable component. In practical applications, for frame (shear) structure buildings, the load-bearing components are reinforced concrete columns, reinforced concrete shear walls, and beams. In this embodiment, reinforced concrete columns are selected as the experimental object.

[0053] Obtain the building's structural plan layout, determine the reinforced concrete columns to be tested, and obtain the column's dimensions, concrete strength grade, and reinforcement details. Select a certain length in the middle of the column as the test object.

[0054] Specifically: For buildings slated for demolition, considering the varying stresses on load-bearing columns at different locations within a frame structure, the central column is generally selected as the test object; for damaged buildings requiring reinforcement, the columns requiring reinforcement or modification are selected as the test objects. To facilitate subsequent strain data analysis, the cutting range can be relatively large, for example, around 1 meter.

[0055] Step 202: Cut the first load-bearing component according to the cutting range, and measure the strain of the first load-bearing component during the cutting process. The strain includes a first strain and a second strain; the first strain is obtained by measuring the strain of the load-bearing component using a non-contact full-field strain measurement system; the second strain is obtained by measuring the strain of the load-bearing component using a strain gauge. The non-contact full-field strain measurement system consists of a CCD camera, lens, analysis software, graphics workstation, support, and lamp.

[0056] Before step 202, the following is also included:

[0057] Speckle patterns are evenly distributed within the cutting range; the speckles are used to measure the strain of the first load-bearing component using a non-contact full-field strain measurement system.

[0058] The strain gauge is attached to a designated position on the first load-bearing component, specifically including:

[0059] The preset position is then subjected to plaster removal and sanding to obtain the processed preset position.

[0060] The strain gauge is attached to the preset position after the treatment.

[0061] In practical applications, speckle patterns are evenly distributed within the cutting range along the observation direction of the column, strain gauges are attached within the testing range, and a static strain gauge is used to collect strain data throughout the cutting process. At the same time, a GoPro camera (CCD camera) is used to record the changes in speckle patterns.

[0062] like Figure 3 As shown, with the observation surface facing forward, transverse and longitudinal strain gauges are attached to the center of the four sides of the test object. Transverse and longitudinal strain gauges are also attached to the center of the left and right sides at a distance of 0.3m from the cutting line, for a total of 16 strain gauges. Before attaching the strain gauges, the column surface should be pre-treated by removing the plaster layer and grinding the areas where the gauges will be attached to ensure a smooth and flat surface. In this embodiment, the strain values ​​of the transverse strain gauges are not used when calculating the stress.

[0063] The front of the test object is the observation surface. Speckle pattern C is sprayed onto the observation surface, and transverse strain gauges A1-A8 and longitudinal strain gauges B1-B8 are attached. After attachment, the strain gauges are waterproofed. The strain gauges are connected to the static data acquisition instrument D via strain acquisition lines. Changes in the speckle pattern are recorded at camera observation point E.

[0064] Step 203: Perform a loading test on the cut-off load-bearing component using a pressure testing machine, and collect the first acoustic emission signal of the cut-off load-bearing component using a first acoustic emission sensor. In practical applications, loading is performed using a pressure testing machine, while the acoustic emission signal is monitored using an acoustic emission device (first acoustic emission sensor).

[0065] Step 203 specifically includes:

[0066] The cut-off load-bearing components are processed to obtain standard specimen 3; the standard specimen 3 is a cylinder with a diameter of 50mm and a height of 100mm.

[0067] The standard specimen was subjected to a loading test using a pressure testing machine, and the first acoustic emission signal of the standard specimen was collected using a first acoustic emission sensor. Loading was stopped when the standard specimen reached 80% of its ultimate bearing capacity.

[0068] After measuring the diameter and height of the standard specimen 3, a thin layer of coupling agent is applied to both ends of the standard specimen 3. The acoustic emission sensor 5 is then fixed to the standard specimen 3 with tape. Figure 4 As shown, the standard specimen 3 is placed on the base 6 of the pressure testing machine, and pressure is applied through the pressure head 1 of the pressure testing machine. The axial deformation sensor 2 and the circumferential deformation sensor 4 are adjusted, and the loading system and acoustic emission system are debugged.

[0069] After completing the preparations, begin loading and stop the experiment when the load reaches 80% of the ultimate bearing capacity of standard specimen 3.

[0070] In practical applications, the field experimental data (i.e., the first strain and the second strain) and the loading experimental data (i.e., the first acoustic emission signal) are saved and preliminarily analyzed to ensure the validity of the data. The specific analysis steps are as follows:

[0071] Step 204: Determine the first load on the first load-bearing component based on the first strain, and determine the second load on the first load-bearing component based on the second strain.

[0072] Specifically, the first and second initial stresses are calculated using the stress calculation formula σ=E·ε; where σ is the stress, E is the elastic modulus of the reinforced concrete (component), and ε is the strain.

[0073] Then, calculate the first load based on the first initial stress, and calculate the second load based on the second initial stress.

[0074] Step 205: Determine the third load on the first load-bearing component based on the first acoustic emission signal. In practical applications, the Kessel effect is used to determine the third load on the first load-bearing component based on the first acoustic emission signal. The value corresponding to the Kessel effect point is the third load.

[0075] Step 206: Determine whether the errors between the first load and the second load, the first load and the third load, and the second load and the third load are all within a preset range. If yes, proceed to step 207; otherwise, proceed to step 208.

[0076] Step 207: Take the average value of the first load, the second load, and the third load as the maximum load of the first load-bearing component.

[0077] Step 208: Return to "Step 201" until the errors between the first load and the second load, the first load and the third load, and the second load and the third load are all within the preset range.

[0078] Example 2

[0079] Core samples are taken from the secondary load-bearing components of buildings to be demolished or reinforced. These secondary load-bearing components are non-removable. In practical applications, core samples should ideally be taken from the middle of the component. Core sampling is not recommended at joints and edges where concrete stress is complex, and core sampling should be avoided on beams whenever possible. Reinforcing steel bars should be avoided during core sampling. At least three core samples should be taken from each secondary load-bearing component, and at least two from smaller components. The core sample dimensions are 50mm in diameter and 100mm in height.

[0080] The core sample was subjected to a loading test using a pressure testing machine, and the second acoustic emission signal of the standard specimen was collected using a second acoustic emission sensor.

[0081] The maximum load of the second load-bearing component is determined based on the second acoustic emission signal.

[0082] The comprehensive experimental method for obtaining the maximum load of load-bearing components proposed in this invention can be flexibly applied. Under certain circumstances, it can accurately obtain the initial stress state inside the load-bearing components without affecting the safe use of the building. The combination of multiple measurement methods makes the results more reliable, providing a new method for obtaining the maximum load of load-bearing components of tall buildings.

[0083] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0084] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A comprehensive experimental method for obtaining the maximum load of a load-bearing component, characterized in that, For removable components, including: Determine the cutting range on the first load-bearing component of the building to be demolished or reinforced; the first load-bearing component is a removable component; The first load-bearing component is cut according to the cutting range, and the strain of the first load-bearing component is measured during the cutting process; the strain includes a first strain and a second strain; the first strain is obtained by measuring the strain of the first load-bearing component using a non-contact full-field strain measurement system; the second strain is obtained by measuring the strain of the first load-bearing component using a strain gauge. A load test was conducted on the cut-off load-bearing component using a pressure testing machine, and the first acoustic emission signal of the cut-off load-bearing component was collected using a first acoustic emission sensor. The first load on the first load-bearing component is determined based on the first strain, and the second load on the first load-bearing component is determined based on the second strain. The third load on the first load-bearing component is determined based on the first acoustic emission signal; Determine whether the errors between the first load and the second load, the errors between the first load and the third load, and the errors between the second load and the third load are all within a preset range; If so, the average value of the first load, the second load, and the third load shall be taken as the maximum load of the first load-bearing component; If not, return to the step of "determine the cutting range on the first load-bearing component in the building to be demolished or reinforced and repaired" until the errors of the first load and the second load, the first load and the third load, and the second load and the third load are all within the preset range.

2. The comprehensive experimental method for obtaining the maximum load of a load-bearing component according to claim 1, characterized in that, A load test is performed on the cut-off load-bearing component using a pressure testing machine, and the first acoustic emission signal of the cut-off load-bearing component is collected using a first acoustic emission sensor, specifically including: The cut-off load-bearing components are processed to obtain standard test pieces; the standard test pieces are cylinders. The standard specimen was subjected to a loading test using a pressure testing machine, and the first acoustic emission signal of the standard specimen was collected using a first acoustic emission sensor.

3. The comprehensive experimental method for obtaining the maximum load of a load-bearing component according to claim 1, characterized in that, The third load on the first load-bearing component is determined based on the first acoustic emission signal, specifically including: Using the Kessel effect, the third load on the first load-bearing component is determined based on the first acoustic emission signal.

4. The comprehensive experimental method for obtaining the maximum load of a load-bearing component according to claim 2, characterized in that, The loading test is stopped when the load reaches 80% of the ultimate bearing capacity of the standard specimen.

5. The comprehensive experimental method for obtaining the maximum load of a load-bearing component according to claim 1, characterized in that, The first strain of the strain gauge was acquired using a static strain gauge.

6. The comprehensive experimental method for obtaining the maximum load of a load-bearing component according to claim 1, characterized in that, Before cutting the first load-bearing member according to the cutting range and measuring the strain of the first load-bearing member during the cutting process, the method further includes: Speckle patterns are evenly distributed within the cutting range; the speckles are used to measure the strain of the first load-bearing component using a non-contact full-field strain measurement system. The strain gauge is attached at the designated position on the first load-bearing component.

7. The comprehensive experimental method for obtaining the maximum load of a load-bearing component according to claim 6, characterized in that, The strain gauge is attached to a designated position on the first load-bearing component, specifically including: The plaster layer was removed and the area was sanded to obtain the processed preset location. The strain gauge is then attached to the designated position after the treatment.

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