A method for detecting the bearing capacity of floor slabs

Abstract

The present invention relates to a method for detecting the bearing capacity of a floor slab, and belongs to the field of structural detection technology. First, a vibrator is used to vibrate the floor slab according to the frequency corresponding to the first-order formation, and the vertical deformation time history curve of the floor slab is collected to obtain the potential energy change E1 of the floor slab caused by the vibration; then, the equivalent static uniformly distributed load q is calculated, and the equivalent static uniformly distributed load-deformation value curve is drawn; finally, the bearing capacity of the floor slab is determined according to the equivalent static uniformly distributed load-deformation value curve. The present invention utilizes sensors and vibrators, and utilizes scientific calculation methods to accurately measure the dynamic deformation of the vibrated floor slab, which can effectively evaluate the structural bearing capacity of the floor slab and can quickly detect the floor slab in construction projects.

Description

Technical Field

[0001] The invention relates to a method for detecting the bearing capacity of a floor slab, and belongs to the technical field of structure detection. Background Art

[0002] There are two methods for assessing the bearing capacity of existing structures: the first is to calculate the bearing capacity based on structural inspection results, and the second is to verify the structural performance. Currently, the first method is mostly used, as structural performance verification methods are relatively rare and not yet fully developed. Floor slab load testing is a structural performance test of floor slabs, and while it has some application in engineering, this method is difficult and time-consuming to implement, limiting its widespread use.

[0003] The existing floor load test method is as follows: based on the design load of the floor and different load combination conditions, a step-by-step unloading system and unloading method are adopted. After each level of loading, the deformation of the floor is measured and a deformation measurement curve is drawn. However, this method has the following problems:

[0004] 1. It requires a lot of loading and unloading, a lot of counterweights and manpower;

[0005] 2. The upper surface of the floor needs to be loaded, and the lower surface needs to be equipped with displacement meters, which places high demands on the site.

[0006] 3. The test time is long.

[0007] Therefore, it is urgent to develop a method that does not require stacking, can effectively reduce manpower and counterweights, and can quickly perform floor bearing capacity testing. Summary of the Invention

[0008] In order to solve the above problems in the prior art, the present invention proposes a floor slab bearing capacity detection method for realizing rapid detection of the floor slab.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions

[0010] A method for detecting the bearing capacity of a floor slab, characterized by comprising the following steps:

[0011] Step 1: Detect the frequency corresponding to the first-order formation of the floor;

[0012] Step 2: Use an exciter to vibrate the floor slab according to the frequency corresponding to the first-order formation. Use at least five different excitation forces to vibrate the floor slab until it reaches a stable vibration state, and collect the vertical deformation time history curves of the floor slab respectively.

[0013] Step 3: Based on the magnitude of the exciting force in step 2 and the maximum speed of the floor during vibration, the potential energy change E1 of the floor caused by the excitation is obtained. At this time, the maximum deformation corresponding to E1 is s1;

[0014] Before vibration excitation begins, the floor slab is deformed under the existing load and has initial potential energy. Furthermore, the plane where the floor slab is located is in equilibrium before vibration excitation. After vibration excitation forms a steady state, the kinetic energy of the measuring point is maximum when it passes through the equilibrium position, and the potential energy is maximum at the maximum deformation s1. The difference between the potential energy at this time and the initial potential energy at the equilibrium position is converted from the maximum kinetic energy, which is the change in floor slab potential energy E1 caused by this vibration excitation.

[0015] Step 4: Considering that the formation at this time is a first-order formation, the potential energy change is the same as that under the action of static load. Assume that under the action of an equivalent static uniformly distributed load q, the same deformation under the action of static load can be produced. Under this deformation, the potential energy change of the floor slab is also E1;

[0016] At this time, the equivalent static uniformly distributed load q is calculated as follows:

[0017] Assume that after the equivalent static uniformly distributed load q is applied, the floor slab deforms, with the maximum deformation being s1. The work done by the equivalent static uniformly distributed load q is as follows:

[0018] W=∫∫qwdxdy=qΩ

[0019] Where: W is the work done by the external load, that is, the work done by the equivalent static uniformly distributed load q, in kN·m; q is the equivalent static uniformly distributed load, in kN / m 2 ; w is the displacement of the load point caused by unit rotation, unit is m; Ω is the volume between the position where the floor sags due to vibration and the original plane, unit is m 3 ;

[0020] Let E1 = W, and q = E1 / Ω, so we can get the equivalent static uniformly distributed load q under this excitation. The maximum displacement measured by this excitation is the maximum deformation s1 corresponding to the equivalent static uniformly distributed load.

[0021] Step 5: According to step 4, the equivalent static uniformly distributed load q is calculated for the above-mentioned at least 5 different exciting forces. Based on the calculation results, a curve of the equivalent static uniformly distributed load q and the maximum deformation s1 is plotted, i.e., the equivalent static uniformly distributed load-deformation value curve;

[0022] Step 6: Determine the floor slab bearing capacity based on the equivalent static uniformly distributed load-deformation value curve.

[0023] Furthermore, a vibration exciter and a vibration pickup are used when vibrating the floor slab, and the vibration exciter and the vibration pickup are connected to the control and receiving devices respectively.

[0024] Furthermore, the exciter is a DH40500 exciter.

[0025] Furthermore, the vibration pickup is a 941B ultra-low frequency vibration pickup.

[0026] Furthermore, the control and receiving device includes a power amplifier, a sweep frequency signal generator and a data acquisition instrument.

[0027] Furthermore, the sweep frequency signal generator is a DH1301 sweep frequency signal generator, which can generate a sine signal, a linear sweep frequency signal, a logarithmic sweep frequency signal, and a pseudo-random signal.

[0028] Furthermore, the power amplifier is a DH5874 power amplifier, which is used to drive the exciter as a high-power excitation source for vibration testing and vibration measurement.

[0029] Furthermore, the data acquisition instrument adopts a universal dynamic signal test and analysis system with more than 8 independent sampling channels, and the sampling rate of each sampling channel is up to 256kHz.

[0030] The technical solution of the present invention has achieved the following beneficial effects:

[0031] The present invention utilizes sensors and vibrators and scientific calculation methods to accurately measure the dynamic deformation of the excited floor slab, can effectively evaluate the structural bearing capacity of the floor slab, can quickly detect the floor slab during construction projects, improve the quality of construction projects, is simple to operate, non-destructive, and has good social and economic benefits.

[0032] This method does not require stacking, reduces manpower and counterweights, and can quickly detect the bearing capacity of the floor slab. At the same time, it only requires the arrangement of sensors on the surface of the floor slab, which reduces the requirements on the site. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the equivalent static uniformly distributed load-deformation value curve obtained by the present invention;

[0034] Figure 2 is the equivalent static uniformly distributed load-deformation value curve. DETAILED DESCRIPTION

[0035] Combined with attachment Figure 1-2 The embodiments of the present invention are described in detail.

[0036] A floor slab bearing capacity detection method of the present invention specifically comprises the following steps:

[0037] Step 1: Detect the frequency corresponding to the first-order formation of the floor.

[0038] Step 2: Use an exciter to vibrate the floor slab according to the frequency corresponding to the first-order formation. Use at least 5 times of exciting forces of different magnitudes to vibrate the floor slab to achieve a stable vibration state, and collect the vertical deformation time history curves of the floor slab respectively.

[0039] Step 3: Based on the magnitude of the exciting force in step 2 and the maximum speed of the floor during vibration, the potential energy change E1 of the floor caused by the excitation is obtained. At this time, the maximum deformation corresponding to E1 is s1.

[0040] Before vibration excitation begins, the floor slab is deformed under the existing load and has initial potential energy. The floor slab is in equilibrium before vibration excitation. After vibration reaches a steady state, the kinetic energy of the measurement point is maximum when it passes through the equilibrium position, and the potential energy is maximum at maximum deformation s1. The difference between this potential energy and the initial potential energy at the equilibrium position is the conversion of the maximum kinetic energy, which is the change in floor slab potential energy E1 caused by this vibration excitation.

[0041] Step 4: Considering that the formation at this time is a first-order formation, the potential energy change is the same as that under the action of static load. Assuming that under the action of an equivalent static uniformly distributed load q, the same deformation under the action of static load can be produced. Under this deformation, the potential energy change of the floor slab is also E1.

[0042] At this time, the equivalent static uniformly distributed load q is calculated as follows:

[0043] Assume that after the equivalent static uniformly distributed load q is applied, the floor slab deforms, with the maximum deformation being s1. The work done by the equivalent static uniformly distributed load q is as follows:

[0044] W=∫∫qwdxdy=qΩ

[0045] Where: W is the work done by the external load, i.e. the work done by the equivalent static uniformly distributed load q, in kN·m. q is the equivalent static uniformly distributed load, in kN / m 2 w is the displacement of the load point caused by unit rotation, unit is m. Ω is the volume between the position where the floor sags due to the excitation and the original plane, unit is m 3 .

[0046] Let E1 = W, and q = E1 / Ω, so we can get the equivalent static uniformly distributed load q under this excitation, and the maximum displacement measured by this excitation is the maximum deformation s1 corresponding to the equivalent static uniformly distributed load.

[0047] Step 5: According to step 4, calculate the equivalent static uniformly distributed load q for at least 5 different exciting forces mentioned above, and draw the equivalent static uniformly distributed load q according to the calculation results. Figure 1 The curve of equivalent static uniformly distributed load q and maximum deformation s1 shown is the equivalent static uniformly distributed load-deformation value curve.

[0048] Step 6: Determine the floor slab bearing capacity based on the equivalent static uniformly distributed load-deformation value curve.

[0049] When vibrating the floor slab, a combination of existing equipment is used, including an exciter and a pickup, which are connected to the control and receiving devices respectively. In this embodiment, the exciter is a DH40500 exciter, which can be used for environmental vibration and fatigue testing of large parts and for measuring the dynamic response of large structures. The pickup is a 941B ultra-low frequency pickup. The 941B ultra-low frequency pickup is a dynamic reciprocating pickup. Due to the use of passive servo feedback technology, it can achieve ultra-low frequency (as low as 0.17Hz) and large displacement (600mm) vibration measurement. It has the characteristics of wide bandwidth, high resolution, large dynamic range, and good impact resistance, and is suitable for vibration testing and monitoring of various structures, such as pulsation testing and vibration monitoring of the ground and various structures. It can also be used for pulsation testing of general engineering structures such as bridges, buildings, docks, dams, offshore platforms, etc., and vibration measurement and monitoring in various vibration tests. It can also be used to measure weak vibrations of isolation platforms. It can also be used to measure ultra-low frequency and large amplitude values ​​of highly flexible structures such as suspension bridges. The control and receiving device consists of a power amplifier, a swept frequency signal generator, and a data acquisition device. The swept frequency signal generator is a DH1301, capable of generating sinusoidal, linear, logarithmic, and pseudo-random signals, with a peak output power of 60W. This generator can vibrate test specimens to measure their natural oscillation frequency, and is widely used in vibration measurement applications in machinery manufacturing and transportation. The power amplifier is a DH5874, which drives the vibrator. This high-power source is widely used in vibration research and experiments in the aviation, aerospace, machinery, construction, and transportation sectors. The data acquisition device utilizes a general-purpose dynamic signal test and analysis system with over eight independent sampling channels, each with a sampling rate of up to 256kHz. Its wide range of applications includes testing and analyzing various physical quantities, including strain, vibration (acceleration, velocity, and displacement), shock, torque, and pressure. It has over eight independent sampling channels, each with a sampling rate of up to 256kHz.

[0050] The specific embodiments are as follows:

[0051] The floor slab measures 4000mm*4000mm, is 130mm thick, is fixed on all four sides, and has a concrete strength grade of C30. Steady-state excitation is performed using excitation forces of 0.5kN, 1kN, 1.5kN, 2kN, and 2.5kN, respectively.

[0052] Step 1: Simulate in the software and find that the frequency corresponding to the first-order formation of the floor is 10.2HZ;

[0053] Step 2: Excite the floor slab using a first-order frequency, using excitation forces of 0.5 kN, 1 kN, 1.5 kN, 2 kN, and 2.5 kN for steady-state excitation. Collect the maximum velocity and maximum vertical displacement s1 of the floor slab.

[0054] The steady-state amplitudes (i.e., maximum deformation s1) of the structure are 0.8 mm, 1.5 mm, 2.4 mm, 3.3 mm, and 4.0 mm, respectively. At the same time, the maximum velocities of the floor slabs at the equilibrium position under steady-state excitation are 0.101 m / s. 2 , 0.211m / s 2 , 0.309m / s 2 , 0.412m / s 2 , 0.52m / s 2 .

[0055] Step 3: Based on the velocity obtained in step 2, calculate the kinetic energy of the floor, which is equal to the potential energy of the floor. Under different excitations, the values ​​are 6.6 J, 28.9 J, 62.1 J, 110.3 J, and 175.8 J, respectively.

[0056] Step 4: Considering that the formation at this time is a first-order formation, the potential energy change is the same as that under the action of static load. Assume that under the action of an equivalent static uniformly distributed load q, the same deformation under the action of static load can be produced. Under this deformation, the potential energy change of the floor slab is also E1;

[0057] At this time, the equivalent static uniformly distributed load q is calculated as follows:

[0058] Assume that after the equivalent static uniformly distributed load q is applied, the floor slab deforms, with the maximum deformation being s1. The work done by the equivalent static uniformly distributed load q is as follows:

[0059] W=∫∫qwdxdy=qΩ

[0060] Where: W is the work done by the external load, that is, the work done by the equivalent static uniformly distributed load q, in kN·m; q is the equivalent static uniformly distributed load, in kN / m 2 ; w is the displacement of the load point caused by unit rotation, unit is m; Ω is the volume between the position where the floor sags due to vibration and the original plane, unit is m 3 .

[0061] According to the above formula, the equivalent static load of the floor slab under different potential energies is calculated to be 1.6kN,

[0062] 3.6kN, 4.8kN, 6.3kN and 8.2kN.

[0063] Step 5: Draw the equivalent static uniformly distributed load q under different exciting forces for 5 times and calculate the equivalent static uniformly distributed load q and the maximum deformation s1 according to the calculation results, that is, the equivalent static uniformly distributed load-deformation value curve, as shown in the figure. Figure 2 shown.

[0064] Step 6: According to the above equivalent static uniformly distributed load-deformation value curve, the maximum floor bearing capacity can reach 8.24kN / m 2 , can carry the floor load in general design.

[0065] In summary, although the embodiments of the present invention have been described, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments without departing from the principles and purpose of the present invention.

Claims

1. A method for detecting the bearing capacity of a floor slab, characterized in that: The steps include: Step 1: Detect the frequency corresponding to the first-order formation of the floor; Step 2: Use an exciter to vibrate the floor slab according to the frequency corresponding to the first-order formation. Use at least five different excitation forces to vibrate the floor slab until it reaches a stable vibration state, and collect the vertical deformation time history curves of the floor slab respectively. Step 3: Based on the magnitude of the exciting force in step 2 and the maximum speed of the floor during vibration, the potential energy change E1 of the floor caused by the excitation is obtained. At this time, the maximum deformation corresponding to E1 is s1; Before vibration excitation begins, the floor slab is deformed under the existing load and has initial potential energy. Furthermore, the plane where the floor slab is located is in equilibrium before vibration excitation. After vibration excitation forms a steady state, the kinetic energy of the measuring point is maximum when it passes through the equilibrium position, and the potential energy is maximum at the maximum deformation s1. The difference between the potential energy at this time and the initial potential energy at the equilibrium position is converted from the maximum kinetic energy, which is the change in floor slab potential energy E1 caused by this vibration excitation. Step 4: Considering that the formation at this time is a first-order formation, the potential energy change is the same as that under the action of static load. Assume that under the action of an equivalent static uniformly distributed load q, the same deformation under the action of static load is generated. Under this deformation, the potential energy change of the floor slab is also E1; At this time, the equivalent static uniformly distributed load q is calculated as follows: Assume that after the equivalent static uniformly distributed load q is applied, the floor slab deforms, with the maximum deformation being s1. The work done by the equivalent static uniformly distributed load q is as follows: W=∫∫qwdxdy=qΩ Where: W is the work done by the external load, that is, the work done by the equivalent static uniformly distributed load q, in kN·m; q is the equivalent static uniformly distributed load, in kN / m 2 ; w is the displacement of the load point caused by unit rotation, unit is m; Ω is the volume between the position where the floor sags due to vibration and the original plane, unit is m 3 ; Let E1 = W, and q = E1 / Ω, thus obtaining the equivalent static uniformly distributed load q under this excitation. The maximum displacement measured by this excitation is the maximum deformation corresponding to the equivalent static uniformly distributed load, s1; Step 5: According to step 4, calculate the equivalent static uniformly distributed load q for the above-mentioned at least five different excitation force conditions. Based on the calculation results, draw a curve of the equivalent static uniformly distributed load q and the maximum deformation s1, i.e., the equivalent static uniformly distributed load-deformation value curve; Step 6: Determine the floor slab bearing capacity based on the equivalent static uniformly distributed load-deformation value curve.

2. A floor slab bearing capacity detection method according to claim 1, characterized in that: When the floor slab is excited, a vibration exciter and a vibration pickup are used, and the vibration exciter and the vibration pickup are connected to the control and receiving devices respectively.

3. A floor slab bearing capacity detection method according to claim 2, characterized in that: The exciter is a DH40500 exciter.

4. A floor slab bearing capacity detection method according to claim 2, characterized in that: The vibration pickup is a 941B ultra-low frequency vibration pickup.

5. A floor slab bearing capacity detection method according to claim 2, characterized in that: The control and receiving device includes a power amplifier, a sweep frequency signal generator and a data acquisition instrument.

6. A floor slab bearing capacity detection method according to claim 5, characterized in that: The sweep frequency signal generator is a DH1301 sweep frequency signal generator, which can generate sinusoidal signals, linear sweep frequency signals, logarithmic sweep frequency signals, and pseudo-random signals.

7. A floor slab bearing capacity detection method according to claim 5, characterized in that: The power amplifier is a DH5874 power amplifier, which is used to drive the exciter and serve as a high-power excitation source for vibration testing and vibration measurement.

8. A floor slab bearing capacity detection method according to claim 5, characterized in that: The data acquisition instrument adopts a universal dynamic signal test and analysis system, has more than 8 independent sampling channels, and the sampling rate of each sampling channel is up to 256kHz.

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