A plate beam detection device using self-balancing theory and a beam mechanics detection method

Abstract

The present invention discloses a plate beam detection device and a beam mechanics detection method using the self-balancing theory. The device includes: a beam for testing the loading force; an I-beam installed on the beam; a jack erected on the I-beam; a steel plate installed on the top surface of the jack; and a steel wire cable connected between the beam and the steel plate. The method of the present invention includes the following steps: evaluating the actual quality based on the total deflection at the mid-span of the beam, the stress at the upper end of the mid-span of the beam, and the stress at the lower end of the mid-span of the beam calculated. The present invention applies the theory of the planar cable-stayed beam to the bending resistance detection of the beam, making the entire detection system of the beam a self-balancing system. The strut is replaced by a jack. During loading, there is no need for an external large-scale lifting machine to lift heavy objects. Only by selecting a suitable steel cable and restricting the elongation of the jack can the force on the beam be achieved, making the loading process simple and convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and particularly relates to a slab beam detection device and a beam mechanics detection method using the self-balancing theory. Background Art

[0002] To ensure the quality of reinforced concrete bridges, on-site test detections are usually required for single precast beams. Limited by the on-site test conditions, for a single slab beam, on-site tests often require cranes, loading counterweights, loading brackets (steel beams), jacks, steel wires, etc. The on-site assembly is rather cumbersome and very inconvenient, making the detection process troublesome and inefficient, and having certain potential safety hazards. Therefore, it is very necessary to develop a simple and convenient loading method. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a slab beam detection device and a beam mechanics detection method using the self-balancing theory.

[0004] The present invention applies the theory of planar cable-stayed beams to the mechanical property detection of beams, making the entire detection system of the beam a self-balancing system. The strut is replaced by a jack. During loading, it is not necessary to use an external large lifting machine to lift heavy objects. Only by selecting appropriate steel cables and controlling the elongation of the jack can the force on the beam be realized, making the loading process simple and convenient.

[0005] A slab beam detection device using the self-balancing theory includes:

[0006] A test beam;

[0007] An I-beam installed on the test beam;

[0008] A jack standing upright on the I-beam;

[0009] A steel plate installed on the top surface of the jack;

[0010] A steel wire cable connecting the test beam and the steel plate.

[0011] In the present invention, the steel wire cable makes this system a self-balancing system. It is not necessary to use an external large lifting machine to lift heavy objects to provide a reaction force for the jack. Instead, the tensile force of the steel wire cable is used to restrict the elongation of the jack. The force exerted by the steel wire cable on the beam makes this system no longer a simple structure with compression in the middle of the beam span. While the beam is subjected to a concentrated force at the mid-span position, it is also subjected to a concentrated force at the beam end by the steel wire cable. This force can be decomposed into two parts, the vertical force and the horizontal force on the beam. The horizontal force is equivalent to a horizontal force acting on the beam axis and a bending moment acting at the beam end. This bending moment will affect the mid-span bending moment and deflection of the beam.

[0012] There are three I-beams, among which two I-beams are placed parallel to each other on the test beam, and the other I-beam is placed on the two parallel I-beams.

[0013] The length direction of the I-beam placed on the two parallel I-beams is perpendicular to the length direction of the two parallel I-beams.

[0014] Hook rings are arranged at both ends of the test beam, and the hook rings are semi-circular ring structures.

[0015] Two mounting holes are arranged at both ends of the steel plate.

[0016] One end of the wire cable is hooked on the hook ring, and the other end of the wire cable is hooked on the mounting hole of the steel plate.

[0017] A beam mechanics detection method for a plate beam detection device using the self-balancing theory includes the following steps:

[0018] 1) Calculate the required area A of the steel cable according to the sizes of the jack, I-beam and test beam and the maximum bending moment to be applied. s ;

[0019] 2) Calculate the maximum force F that the jack needs to apply and the corresponding deflection according to the maximum bending moment corresponding to the mid-span of the test beam. q1 And the corresponding deflection;

[0020] 3) Evaluate the actual quality according to the calculated total deflection y at the mid-span of the test beam, 1 the stress σ at the upper end of the mid-span of the test beam, 上 and the stress σ at the lower end of the mid-span of the test beam. 下 Evaluate the actual quality.

[0021] In step 1), the calculation of the required area A of the steel cable s specifically includes:

[0022] a) The selected elastic modulus of the steel cable is E, s , θ 0 is the included angle between the steel cable and the beam when no force is applied. The vertical displacement between the steel plate and the hook ring on the beam when the beam is not stressed is l, x0 , the length L of the beam, E b is the elastic modulus of the beam, I b is the section coefficient of the beam, A b is the cross-sectional area of the beam, M 1 is the maximum bending moment corresponding to the mid-span of the beam;

[0023] b) Calculate the required length l of the steel cable s0 and the required area A of the steel cable s ;

[0024] The length of the required steel cable

[0025] The area A of the required steel cable s Calculation method

[0026] is as follows: l x1 is the vertical displacement between the steel plate and the hook on the beam after being stressed. To calculate the total area of the steel cable, a l needs to be determined artificially x1 The maximum elongation λ max of l, whose value is between 0 and 0.1. When the jack is loaded, the maximum value l x1,max of l x1,max =(1 + λ max )l x0 . A s The calculation formula of A is:

[0027]

[0028] where h is the cross-sectional height of the test beam, A 1 is the cross-sectional area of a single steel cable, represents rounding up to the nearest integer.

[0029] In step 2), the maximum force F that the jack needs to load is calculated according to the maximum bending moment corresponding to the mid-span of the test beam q1 and the corresponding deflection, specifically including:

[0030]

[0031] l x1 The expression of l

[0032]

[0033] Δ 1 =c 2 -3bd + 12aeΔ 2 =2c 3 -9bcd + 27ad 2 +27b 2 e - 72ace

[0034] Where:

[0035] a = 4t 2 L 2 b = 4t 2 L 2 h - 32M 1 tL c = h 2 t 2 L 2 -16M 1 tLh + 64M 12 +t 2 L 4 -4t 2 L 2 l s0 2

[0036] d = -4ht 2 L 2 l s0 2 +ht 2 L 4 -8M 1 tL 3

[0037] t is

[0038] the total deflection y at the mid-span of the test beam 1 :

[0039]

[0040] the stress σ at the upper end of the mid-span of the test beam 上 and the stress σ at the lower end of the mid-span of the test beam 下 are respectively:

[0041]

[0042]

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] The device of the present invention utilizes the concept of a self-balanced system to achieve the detection of the mechanical properties of a beam. For the conventional detection of the mechanical properties of a beam, a jack is used to apply pressure to the mid-span of the beam to test the maximum deflection and stress at the mid-span. The loading process requires a crane, loading weights, loading brackets (steel beams), etc., making on-site detection extremely inconvenient. Compared with the traditional process, this device uses the connection of steel cables to the beam to make the entire structure a self-balanced structure. By using the restraint of the steel cables and applying load with a jack, large equipment is not required, making the detection of this method convenient. The target parameters (the total deflection y at the mid-span of the beam 1 , the stress σ at the upper end of the mid-span of the beam 上 and the stress σ at the lower end of the mid-span of the beam 下 ) obtained by detecting with the device and method of the present invention are highly accurate, simple and fast, and are beneficial to market promotion and utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic structural diagram of the plate beam detection device using the self-balanced theory in the present invention;

[0046] Figure 2 is the sectional view of the test beam;

[0047] Figure 3 is the structural schematic diagram of the connection between the steel wire cable and the test beam;

[0048] Figure 4 is the structural schematic diagram of the connection between the steel wire cable and the steel plate;

[0049] In the figure: 1 - test beam, 2 - I-beam, 3 - jack, 4 - steel wire cable, 5 - steel plate, 6 - hook loop embedded part. Specific implementation mode

[0050] The following further describes the invention in conjunction with the accompanying drawings and embodiments.

[0051] As Figure 1 shown, a slab beam detection device using the self-balancing theory includes: a test beam 1, three I-beams 2 installed on the test beam 1 and placed under the jacks, two of the three I-beams 2 are placed parallel on the test beam 1, and the other I-beam is placed on the two parallel I-beams, a jack 3 standing upright on the I-beam 2, a steel wire cable 4 connecting the jack 3 and the test beam 1, the steel wire cable 4 is directly hooked on the hook loop embedded part 6 of the test beam 1 (the hook loop embedded part 6 forms a ring structure, forming a semi-circular ring structure hook loop, which is convenient for the steel wire cable 4 to be directly hooked with a hook), a steel plate 5 with holes on both sides is placed on the jack 3, and the steel wire cable 4 is directly hooked on the perforated steel plate. The steel wire cable 4 makes this system a self-balancing system, without the need for an external large lifting machine to lift heavy objects to provide a reaction force for the jack 3, and directly uses the tensile tension of the steel wire cable 4 to restrict the elongation of the jack 3; the force exerted by the steel wire cable 4 on the test beam 1 makes this system no longer a simple structure with the middle of the test beam 1 under compression. When the test beam 1 is subjected to a concentrated force at the mid-span position, it is also subjected to the concentrated force of the steel wire cable 4 on the test beam 1. This force can be decomposed into two parts, the vertical force and the horizontal force on the test beam 1. The horizontal force is equivalent to the horizontal force acting on the beam axis and the bending moment acting at the beam end. This bending moment will affect the mid-span bending moment and deflection of the beam.

[0052] As Figure 2 shown, it is the cross-section of the test beam 1. From the cross-section of the test beam 1, it can be seen that the middle part of the test beam 1 is a hollow structure.

[0053] As Figure 1 、 Figure 2 、 Figure 3As shown, the steel wire ropes 4 are respectively hooked to the holes of the steel plate 5 and the hook ring embedded parts 6 of the test beam 1 to form a self-balanced system, and the elongation of the jack is restricted by the tensile stiffness of the steel wire ropes 4. The steel wire ropes 4 are directly hooked to the hook ring embedded parts 6 of the test beam 1, a steel plate 5 with holes on both sides is placed on the jack 3, and the steel wire ropes 4 are directly hooked to the steel plate 5 with holes.

[0054] The minimum number of steel wire ropes 4 can be calculated according to the sizes of the jack 3, the I-beam 2 and the test beam 1 and the maximum bending moment to be applied.

[0055] A beam mechanical detection method for a plate-beam detection device using the self-balanced theory includes the following steps:

[0056] 1) Calculate the required area A of the steel cables according to the sizes of the jack 3, the I-beam 2 and the test beam 1 and the maximum bending moment to be applied s ;

[0057] In step 1), the required area A of the steel cables s The calculation specifically includes:

[0058] a) The selected elastic modulus of the steel cable is E s , θ 0 is the included angle between the steel cable and the beam. The vertical displacement between the steel plate and the hook ring on the beam 1 when the beam 1 is not stressed is l x0 , the length L of the beam 1, E b is the elastic modulus of the beam 1, I b is the section modulus of the beam 1, A b is the cross-sectional area of the beam 1, M 1 is the maximum bending moment corresponding to the mid-span of the beam 1;

[0059] b) Calculate the length l s0 of the required steel cables (i.e., the steel wire ropes 4) and the required area A s of the required steel cables,

[0060]

[0061] The calculation method of the required area A s of the steel cables is as follows: l x1 is the vertical displacement between the steel plate and the hook ring on the beam after being stressed. To calculate the total area of the steel cables, a maximum elongation rate λ x1 of l needs to be determined artificially. Its value is between 0 and 0.1. When the jack is loaded, the maximum value l max of l x1,max =(1 + λ x1,max )l max x0 .

[0062] A s The calculation formula of is:​

[0063]

[0064] Among them, h is the cross-sectional height of the test beam, and A 1 is the cross-sectional area of a single steel cable, denotes rounding up to the nearest integer;

[0065] 2) Calculate the maximum force F that the jack needs to apply according to the maximum bending moment corresponding to the mid-span of the test beam q1 and the corresponding deflection;

[0066]

[0067] l x1 The expression of

[0068]

[0069] Δ 1 = c 2 - 3bd + 12aeΔ 2 = 2c 3 - 9bcd + 27ad 2 + 27b 2 e - 72ace

[0070] Among them:

[0071] a = 4t 2 L 2 b = 4t 2 L 2 h - 32M 1 tL c = h 2 t 2 L 2 - 16M 1 tLh + 64M 1 2 + t 2 L 4 - 4t 2 L 2 l s0 2

[0072] d = - 4ht 2 L 2 l s0 2 + ht 2 L 4 - 8M 1 tL 3

[0073] t is

[0074] Total mid-span deflection y of Test Beam 1 1 :

[0075]

[0076] Upper-end stress σ at the mid-span of Test Beam 1 上 and lower-end stress σ at the mid-span of the test beam 下 are respectively:

[0077]

[0078]

[0079] 3) Based on the calculated total mid-span deflection y of Test Beam 1 1 , upper-end stress σ at the mid-span of Test Beam 1 上 and lower-end stress σ at the mid-span of Test Beam 1 下 evaluate the actual quality.

[0080] This embodiment is a beam with a length of 13m, and the cross-section is as Figure 2 , the elastic modulus of the beam is 3.45×10 10 Pa. When the maximum bending moment is 360 kN·m, find the deflection of Beam 1 under the action of the corresponding Jack 3. Use a jack with a length of 0.34m and a 12.6a I-beam. The placement method is shown in Figure 1 as shown, l x0 = 0.126 + 0.126 + 0.34 - 0.02 = 0.572m. (0.02 is because the connection between the cable and the beam is not on the beam but on the steel bars fixed on the beam. For the accuracy of the calculation, it needs to be subtracted). The original length l s0 of the cable is 6.525m, and the elastic modulus E s of the cable is 1.15×10 5 MPa, and the diameter is 6cm. A 1 = 2.83×10 -3 m 2 . Assume λ max = 0.0874 < 0.1.

[0081] Calculate the number of steel cables using the formula:

[0082]

[0083] Select an appropriate number of steel cables. Since the selected steel cable area is larger than the required area, the elongation rate of the jack must be less than 0.1.

[0084] To further prove the correctness of the example, perform a calculation and analysis using ABAUQS. The two-dimensional finite element analysis based on ABAUQS is as follows:

[0085] The model of ABAUQS is similar to the theoretical calculation model. The steel cable is simplified to one with an area of 5.66×10 -3 m 2 , and the rest of the data is the same as that in the theoretical analysis part. The steel cable is a truss structure that only bears tension and not compression, and the test beam is a beam structure.

[0086] Since the steel cable acts on the upper part of test beam 1 instead of the central axis, two steel arms are rigidly connected to both ends of test beam 1 respectively. The stiffness of the steel arms and jack 3 is 100 times that of the test beam, and the rotation angle of jack 3 is fixed. Two forces F with the same magnitude and opposite directions are applied to the two points at the bottom of jack 3 and the mid-span of the test beam.

[0087] The theoretical mid-span deflection calculated using the above formula and the lower deflection simulated by ABAUQS are shown in Table 1. The theoretical mid-span bending moment, beam axial force and the mid-span bending moment, beam axial force simulated by ABAUQS are shown in Table 2. The theoretical upper and lower stress values at the mid-span and the upper and lower stress values at the mid-span simulated by ABAUQS are shown in Table 3, and the percentage of relative error between the ABAUQS value and the theoretical calculation is attached.

[0088] Table 1 Comparison table of theoretical mid-span deflection and lower deflection simulated by ABAUQS

[0089]

[0090] Table 2 Comparison table of theoretical mid-span bending moment, beam axial force and mid-span bending moment, beam axial force simulated by ABAUQS

[0091]

[0092] Table 3 Comparison table of theoretical upper and lower stress values at the mid-span and upper and lower stress values at the mid-span simulated by ABAUQS

[0093]

[0094] It can be proved by the example that the relative error between the calculation results of the formula studied in this patent and the calculation results simulated by ABAUQS is within 3%. It shows that the method and formula of this patent are simple and effective.

[0095] The implementation method of the present invention has been described in detail above in combination with the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present invention. The content not described in detail in the specification of the present invention can all adopt the existing technology.

Claims

1. A beam mechanics detection method for a plate - beam detection device using the self - balancing theory, characterized in that, the plate - beam detection device using the self - balancing theory includes: a test beam; I - shaped steel installed on the test beam; a jack standing upright on the I - shaped steel; a steel plate installed on the top surface of the jack; a wire rope connected between the test beam and the steel plate; there are three I - shaped steels. Among them, two I - shaped steels are placed parallel on the test beam, and the other I - shaped steel is placed on the two parallel I - shaped steels. The length direction of the I - shaped steel placed on the two parallel I - shaped steels is perpendicular to the length direction of the two parallel I - shaped steels; the beam mechanics detection method includes the following steps: 1) Calculate the required area A of the steel cable according to the dimensions of the jack, I-beam and test beam and the maximum bending moment to be applied s ; 2) Calculate the maximum force F that the jack needs to apply according to the maximum bending moment corresponding to the mid-span of the beam q1 and the corresponding deflection, specifically including: M 1 is the maximum target bending moment required to be applied at the mid-span of the beam; L is the length of the beam; l x1 The expression of Wherein: t is E s is the elastic modulus of the steel cable, and θ 0 is the initial angle between the steel cable and the beam, and l s0 is the length of the required steel cable, and E b is the elastic modulus of the beam, and I b is the section modulus of the beam, and A b is the cross-sectional area of the beam, and h is the cross-sectional height of the test beam; Total mid-span deflection y of the test beam 1 : The stress σ at the upper end of the mid-span of the test beam 上 and the stress σ at the lower end of the mid-span of the test beam 下 are respectively l x1 is the vertical displacement between the steel plate and the hook on the beam after being stressed; 3) Evaluate the actual quality based on the calculated total mid-span deflection y of the beam 1 , the stress σ at the upper end of the mid-span of the beam 上 and the stress σ at the lower end of the mid-span of the beam 下 .

2. The beam mechanics detection method for a plate - beam detection device using the self - balancing theory according to claim 1, characterized in that, In step 1), the area A of the required steel cable s The calculation specifically includes: a) The selected elastic modulus of the steel cable is E s , θ 0 is the initial angle between the steel cable and the beam. When the beam is not stressed, the vertical displacement between the steel plate and the hook on the beam is l x0 , the length of the beam is L, and E b is the elastic modulus of the beam, and I b is the section modulus of the beam, and A b is the cross-sectional area of the beam, and M 1 is the maximum target bending moment required at the mid-span of the beam; b) Calculate the length l of the required cable s0 and the area A of the required cable s ; Length of the required cable The area A of the required steel cable s The calculation method of the area A of the required steel cable is as follows s The calculation method is as follows: l x1 is the vertical displacement between the steel plate and the hook on the beam after being stressed. To calculate the total area of the steel cable, a l x1 with a maximum elongation rate λ max needs to be artificially determined. Its value is between 0 and 0.

1. When the jack is loaded, l x1,max reaches its maximum value l x1,max =(1 + λ max )l x0 ; A s The calculation formula is as follows: Among them, h is the cross-sectional height of the test beam, and A 1 is the cross-sectional area of a single steel cable, represents rounding up to the nearest integer.

3. The beam mechanics detection method for a plate - beam detection device using the self - balancing theory according to claim 1, characterized in that, hook rings are provided at both ends of the test beam.

4. The beam mechanics detection method for a plate - beam detection device using the self - balancing theory according to claim 3, characterized in that, the hook ring is of a semi - circular ring structure.

5. The beam mechanics detection method for a plate - beam detection device using the self - balancing theory according to claim 3, characterized in that, two mounting holes are provided at both ends of the steel plate.

6. The beam mechanics detection method for a plate - beam detection device using the self - balancing theory according to claim 5, characterized in that, one end of the wire rope is hooked on the hook ring, and the other end of the wire rope is hooked on the mounting hole of the steel plate.

Images