A prestressed threaded rod-angled steel active constraint reinforcement device and method for a column with lapping anchorage defects

Abstract

The present invention provides a prestressed threaded rod - angle steel active restraint reinforcement device and method for columns with lapping and anchoring defects, belonging to the field of structural engineering. The reinforcement device is arranged in multiple layers according to actual conditions. Each layer of structure includes four fine rolling threaded rod systems arranged on the four side faces of a square-section column, rod system attached high-strength bolts arranged at the ends of the fine rolling threaded rod systems, and position adjustment sleeves arranged on the fine rolling threaded rod systems; a pair of high-strength bolts is provided on each fine rolling threaded steel, and the positions of the high-strength bolts are adjusted through the position adjustment sleeves. It also includes four restraint modules, which are fixed on the four top surfaces of the square-section column and used to transmit lateral active restraint forces. The present invention can greatly improve the seismic performance of the reinforced object. It can be finely customized according to columns of different sizes, and according to the given design process, it can reinforce old concrete columns of different ages and different situations.

Description

Technical Field

[0001] The present invention belongs to the field of structural engineering and relates to a reinforcement device and design method for square-section columns, which can be used for the renovation and reinforcement of lapped and anchored square-section columns. Background Art

[0002] Existing reinforced concrete column components mostly connect longitudinal stressed steel bars in a lapped manner. Such construction measures may not meet the requirements of revised and upgraded building codes; in addition, the bottom reinforcement requirements of column components also change with the continuous upgrade of current codes. Therefore, it is necessary to reinforce and transform such components. Applying lateral restraint to components as an effective method to improve the seismic performance of reinforced concrete components has become the mainstream of reinforcement and transformation. Current reinforcement techniques can be divided into two categories: passive restraint and active restraint. The difference between them is that the binding force of passive restraint techniques appears after the component has a lateral deformation, and internal damage has occurred inside the component at this time; the binding force of active restraint techniques appears before the component has a lateral deformation, which can cause a certain degree of pre-strain in the component, thereby offsetting part of the lateral deformation caused by the axial pressure. It can be seen that the service time of the active restraint device is earlier and the effect is better.

[0003] Common active restraint reinforcement methods can be divided into four categories, namely, carbon fiber cloth (FRP) reinforcement under prestress, steel plate (hoop) reinforcement, shape memory metal SMA reinforcement, and other composite reinforcement methods. These methods are applicable to most building structures such as steel-concrete and steel structures, can improve the seismic performance of test pieces and improve the cracking condition, but have limitations such as complex construction and affecting the stiffness of the test pieces themselves. Therefore, an active restraint reinforcement method with simple operation and little impact on the structure itself is needed in engineering. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides an active restraint method for defective columns with lapped and anchored square sections, including an active restraint reinforcement device and a supporting design method. The present invention can be used for rectangular-section beams and columns with binding lapping technology and full-length lapping. The device can be installed in the lapped and anchored area, and its characteristics are: (1) it can be distributed and installed flexibly without affecting the stiffness of the component itself; (2) it can be produced modularly, and users can independently select the required device size and quantity according to the supporting design method of the device.

[0005] In order to achieve the above technical purpose, the technical solution of the present invention is as follows:

[0006] A threaded rod-angled steel active restraint reinforcement device for the reinforcement of square-section columns. The reinforcement device can be arranged in multiple layers according to the design method. Each layer structure includes four rolled thread steel rod systems 1 arranged on the four sides of the square-section column, rod system-attached high-strength bolts 5 arranged at the ends of the rolled thread steel rod systems 1, and position-adjusting sleeves 6 arranged on the rolled thread steel rod systems 1. The rolled thread steel rod system 1 (threaded rod) is a hollow rod-shaped structure with external threads, and a pair of high-strength bolts 5 are carried on each rolled thread steel rod system 1. The position-adjusting sleeve 6 is used to adjust the position of the high-strength bolt 5.

[0007] Furthermore, the threaded rod-angled steel active restraint reinforcement device further includes four restraint modules 2, which are fixed on the four top surfaces of the square-section column and are used to transmit lateral active restraint forces. The contact module 2 is composed of an L-shaped corner contact angle steel 3 and two connecting angle steels 4 fixed on the two outer end faces of the corner contact angle steel 3. Specifically: the inner side surface of the corner contact angle steel 3 is fixedly connected to the square-section column, and the outer side surface is connected to the rolled thread steel rod system 1 through the connecting angle steel 4.

[0008] Furthermore, the connecting angle steel 4 is an L-shaped structure, and one end face is provided with a threaded hole 8 for passing through the rolled thread steel rod system 1, and a structural stiffening rib 7 is provided between the two end faces to ensure the strength of the connecting angle steel 4.

[0009] Furthermore, the number of the position-adjusting sleeves 6 is confirmed according to the design method and actual situation, as long as the high-strength bolt 5 can adjust the prestress through a wrench.

[0010] A threaded rod-angled steel active restraint reinforcement method for the reinforcement of square-section columns, which is realized based on the above reinforcement device. The specific implementation steps are as follows:

[0011] The first step: Determine the lateral restraint force required for reinforcement.

[0012] 1.1: According to the corresponding design manual when designing the lap anchorage defective column that needs to be reinforced, determine the lap length L of the reinforcement object (lap anchorage defective column) s .

[0013] 1.2: After clarifying L s , according to formula (1), calculate the total lateral restraint force F required for reinforcement l .

[0014]

[0015] In the formula, F l is the total lateral restraint force that needs to be applied by the n-layer device, n s is the number of anchoring lap steel bars, and the design method takes the value of 1, L s is the existing lap length of the reinforcement object, d bThe diameter of the longitudinal reinforcement of the object to be strengthened. A b The cross-sectional area of the longitudinal reinforcement, f y The design value / measured value of the yield strength of the longitudinal reinforcement, f’ c The compressive strength of the concrete of the concrete column, and c is the concrete cover thickness. The above formula 1 is from: Harajli M H, Dagher F. Seismic Strengthening of Bond-Critical Regions in Rectangular Reinforced Concrete Columns Using Fiber-Reinforced Polymer Wraps[J]. ACI Structural Journal, 2008, 105(1): 68-77.

[0016] Step 2: Determine the installation position, quantity and size of the constraint module of the device.

[0017] 2.1: Determine the number of installation layers n of the device. The device is installed within the lapping section L s Inside, one layer is arranged at the lap joint, and the remaining arrangement positions are determined according to the project situation. The effective constraint area of the device should cover the entire lap area. The number of installation layers n is determined according to the project situation, and generally n is taken as 2 or 3.

[0018] 2.2: Determine the height B of the device constraint module, and the height can be obtained according to the following formula;

[0019] n(B + 4c) ≥ L s

[0020] Specifically, the value range of B is:

[0021]

[0022] In the formula, n is the number of installation layers, B is the height of the constraint module, c is the concrete cover thickness of the concrete column, and L s is the lap length of the object to be strengthened.

[0023] Furthermore, after determining the number of installation layers n and the height B of the constraint module, the following formula can be used for checking and iterating repeatedly to obtain the optimal solution.

[0024] nB / L s ≤ 0.55

[0025] 2.3: Determine the width of the constraint module. The width w of the constraint module is determined according to the following formula;

[0026] w ∈ [0.2a, 0.5a], a > 0

[0027] Wherein, a is the width of the concrete column.

[0028] 2.4: Determine the thickness t of the constraint module. The thickness of the angle steel of the constraint module is determined according to the following formula;

[0029]

[0030] Wherein, σ s is the yield strength of the material of the constraint module, n is the number of installation layers of the device, B is the height of the constraint module, n and B have been determined in the above steps, and σ s can be obtained by referring to the material parameter table; F T is the tensile force borne by a single precision rolled threaded rod.

[0031] Step 3: Determine the dimensions of the connection module.

[0032] 3.1: Determine the diameter of the threaded rod;

[0033]

[0034] Wherein, F l is the total lateral restraint force required for n sets of devices, n is the number of device layers, F l / n is the required tensile force of each threaded rod on each set of devices, d is the diameter of the threaded rod, and σ b is the yield strength of the material of the threaded rod.

[0035] 3.2: Determine the detailed dimensions of the connection module;

[0036] Furthermore, the detailed dimensions of the connection module need to satisfy the following formula:

[0037]

[0038] Wherein, F l is the total lateral restraint force that needs to be applied for n layers of devices; β f is the increase coefficient of the strength design value of the fillet weld in the front view; d1, b2, b3, h2 are the detailed dimensions of the connection module. Specifically: d1 is the diameter of the threaded hole, b1 is the thickness of the bottom plate of the connection module, b2 is the width of the connecting angle steel, b3 is the length of the connecting angle steel, h1 is the height of the connection module, and h2 is the height from the lower edge of the threaded hole to the lower bottom plate of the connecting angle steel; f f w is the strength design value of the fillet weld. In the design, it is recommended to approximately take h1 = b2 = b3.

[0039] Stage by stage, after completing the above four steps, the device can be processed.

[0040] Step 4: Calculate the required torque.

[0041]

[0042] Wherein, μ' is the friction coefficient. When the processing surface is a dry processing surface, its value is 0.1 - 0.16; when the processing surface is a lubricated processing surface, its value is 0.06 - 0.10. L s is the existing lap length of the object to be strengthened; d b is the diameter of the longitudinal reinforcement of the object to be strengthened; A b is the cross-sectional area of the longitudinal reinforcement; f y is the design value / measured value of the yield strength of the longitudinal reinforcement; f c ' is the compressive strength of the concrete of the concrete column; c is the concrete cover thickness.

[0043] Step 5: Install the device.

[0044] According to the various parameters determined in steps 1 - 3, process and install the device. The steps are as follows:

[0045] 5.1: Clean the raised parts on the surface of the strengthening position to ensure that the corner contact angle steel 3 of the device fits closely with the surface of the object to be strengthened, so as to obtain the best strengthening effect;

[0046] 5.2: Pass the precision rolled threaded steel rod system 1 through the threaded hole 8 on the connecting angle steel 4, and install the displacement adjustment sleeve 6 and the high-strength bolt 5 outside the precision rolled threaded steel rod system 1. At the connection position of the displacement adjustment sleeve 6, connect the four groups of constraint modules of one layer of the device through the precision rolled threaded steel rod system 1 at the specified position. Use a wrench to turn the high-strength bolt 5, and apply the pre-tightening force in two stages. In the first stage, apply 20% of the target torque to each bolt to ensure that the device does not fall off due to gravity at the specified position; in the second stage, apply torque evenly to the four precision rolled threaded steel rods. When the torques on the four threaded rods all reach the target torque, the installation work of the device is completed.

[0047] The beneficial effects of the present invention are:

[0048] (1) It can greatly improve the seismic performance of the object to be strengthened. This device can enhance the bonding ability between the reinforcement and the concrete, thereby greatly improving the ductility of the object to be strengthened, improving the stiffness degradation situation, and finally enhancing the ability of the object to be strengthened to resist damage under earthquake action.

[0049] (2) It can be finely customized according to columns of different sizes. According to the given design process, it can strengthen old concrete columns of different ages and different situations. Description of the Drawings

[0050] Figure 1 is the overall structural schematic diagram of the present invention;

[0051] Figure 2It is the plan view of the device of the present invention;

[0052] Figure 3 It is the schematic diagram of connecting the finish-rolled threaded bar system;

[0053] Figure 4 It is the schematic diagram of the constraint module;

[0054] Figure 5 It is the schematic diagram of the connecting angle steel;

[0055] Figure 6 It is the parameter schematic diagram of the second step 2.1 in the implementation steps;

[0056] Figure 7 It is the parameter schematic diagram of the second steps 2.2 and 2.3 in the implementation steps;

[0057] Figure 8 It is the parameter schematic diagram of the third step in the implementation steps;

[0058] In the figure: 1 Finish-rolled threaded bar system, 2 Constraint module, each constraint module 2 is composed of 3 angle contact angle steels and 4 connecting angle steels; 5 High-strength bolts; 6 Adjusting sleeve; 7 Structural stiffening rib; 8 Thread hole. Specific implementation method

[0059] The following combines the attached drawings and technical solutions, and through design examples, further illustrates the specific implementation method of the device of the present invention.

[0060] A threaded bar-angle steel active constraint reinforcement device for square-section column reinforcement, the reinforcement device can be arranged in multiple layers according to the design method, and the structure of each layer includes four finish-rolled threaded bar systems 1 arranged on the four sides of the square-section column, rod system attached high-strength bolts 5 arranged at the ends of the finish-rolled threaded bar systems 1, and adjusting sleeves 6 arranged on the finish-rolled threaded bar systems 1; the finish-rolled threaded bar system 1 (threaded bar) is a hollow rod-shaped structure with external threads, and a pair of high-strength bolts 5 are provided on each finish-rolled threaded bar system 1; the adjusting sleeve 6 is used to adjust the position of the high-strength bolts 5.

[0061] Design parameters: A square-section reinforced concrete anchorage lap column with a section width of 400 mm, a concrete strength grade of C30, steel bars of HRB400 ribbed steel bars with a diameter of 20 mm, and a lap length of 700 mm. Further, for the above design example, f’ c = 24 Mpa, L s = 700 mm, d b = 20 mm, f y = 360 Mpa, A b = 314.5 mm 2 . The concrete cover thickness C = 40 mm.

[0062] The installation and usage steps are as follows:

[0063] Step 1: Determine the lateral restraint force required for reinforcement.

[0064]

[0065] Step 2: Determine the installation location, quantity of the device and the size of the restraint module.

[0066] The length of the lap joint area is 700 mm. Select three layers for reinforcement, one layer for the lap joint, one layer for the column root, and one layer in the middle. At this time, n = 3.

[0067] According to the formula given in Step 2, calculate the value range of B

[0068] B ∈ [73, 128]

[0069] Take B = 120 mm.

[0070] Check B and n.

[0071] n(B + 4c) = 3×(120 + 4×40) = 840 ≥ L s = 700

[0072] The size is reasonable.

[0073] The value range of the width w of the restraint module is:

[0074] w ∈ [80, 200], a > 0

[0075] Take w = 100 mm.

[0076] The value range of the thickness of the restraint module is

[0077]

[0078] Specifically, n = 3, B = 120 mm, select the common No. 45 steel in the market, σ s = 405.430 Mpa, F T = F l / 3 = 47.91 kN.

[0079] Obtain t ≥ 1.09 mm

[0080] Take t = 20 mm.

[0081] Step 3: Confirm the size of the connection module.

[0082] 3.1: Determine the diameter of the threaded rod;

[0083]

[0084] In the formula, n is the number of installation layers of the device, Fl The total binding force required for the n-layer device, d is the diameter of the threaded rod, and σ b is the yield strength of the material used for the threaded rod, generally taken to be the same as the material of the device. It can be calculated that d ≥ 12.26 mm. For safety, d is taken as 32 mm.

[0085] 3.2: Determine the detailed dimensions of the connection module;

[0086] According to the formula

[0087]

[0088] Take b2 = b3 = h1 = 80 mm, b1 = 10 mm, d1 = d = 32 mm, h2 = 24 mm. Substitute the above parameters into the verification, and it meets the requirements.

[0089] Step 4: Calculate the required torque.

[0090] According to the formula, the required torque is:

[0091]

[0092] Step 5: Carry out the installation work of the device.

[0093] As determined in the first step, the installation layer of the device is 3 layers, and the installation positions are determined as one layer at the joint of the lapping area, one layer at the column root, and one layer in the middle of the lapping area. After determining the installation positions, the specific installation operations can be carried out according to the above steps.

[0094] This device can be applied to the anchored lapped concrete columns designed and constructed according to the old specifications. The test verification results are as follows:

[0095] The reinforced object is a concrete column with a 30d lap joint (d is the diameter of the longitudinal reinforcement, taken as 20 mm in the verification test), and the lap length is 700 mm. After being reinforced by the device, the displacement ductility coefficient of the concrete is increased by 114%. Under different loading levels, the stiffness ratio of the reinforced specimen / unreinforced specimen is up to 1.6 at most, indicating that this device can effectively improve the ductility of the concrete column with insufficient lap length, improve the stiffness degradation situation, and thus improve the seismic performance of the concrete column.

[0096] The above-described embodiments only represent the implementation modes of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for actively constraining and strengthening square-section columns using threaded rods and angle steels, characterized in that The reinforcement method is realized based on a reinforcement device. The reinforcement device arranges a multi-layer structure according to the actual situation. Each layer of the structure includes four sets of high-strength threaded steel bars (1) arranged on the four side surfaces of a square-section column, rod system attached high-strength bolts (5) arranged at the ends of the high-strength threaded steel bar systems (1), displacement adjustment sleeves (6) arranged on the high-strength threaded steel bar systems (1), and four constraint modules (2) fixed on the four top surfaces of the square-section column; the high-strength threaded steel bar systems (1) are hollow rod-shaped structures with external threads, and a pair of high-strength bolts (5) are provided on each high-strength threaded steel bar system (1); the displacement adjustment sleeves (6) are used to adjust the positions of the high-strength bolts (5). The described constraint module (2) is composed of an L-shaped corner contact angle steel (3) and two connecting angle steels (4) fixed on the two outer end faces of the corner contact angle steel (3); the inner side surface of the corner contact angle steel (3) is fixedly connected to the square-section column, and the outer side surface is connected to the high-strength threaded steel bar system (1) through the connecting angle steel (4). The described connecting angle steel (4) is an L-shaped structure, and a threaded hole (8) for passing through the high-strength threaded steel bar system (1) is provided on one end face, and a structural stiffening rib (7) is provided between the two end faces to ensure the strength of the connecting angle steel (4). The reinforcement method includes the following steps: The first step: Determine the lateral restraint force required for reinforcement. 1.1: Determine the strengthening object, i.e., the lap length L of the column with lap and anchorage defects, according to the actual situation s ; 1.2: Confirm L s After that, calculate the total lateral binding force F required for reinforcement l ; Calculate the total lateral binding force F required for reinforcement according to the following formula l : Where, F l is the total lateral restraint force to be applied to the n-layer device, and n s is the number of lapped anchor bars, and the design method takes the value of 1. L s is the existing lap length of the object to be strengthened, and d b is the diameter of the longitudinal reinforcement of the object to be strengthened; A b is the cross-sectional area of the longitudinal reinforcement, and f y is the design value / measured value of the yield strength of the longitudinal reinforcement, and f’ c is the compressive strength of the concrete of the concrete column, and c is the concrete cover thickness; The second step: Determine the installation positions, quantities, and constraint module dimensions of the device. 2.1: Determine the number of installation layers n of the device; the device is installed in the lapping section L s Inside, one layer is arranged at the lapping joint, and the remaining arrangement positions are determined according to the project situation. The effective constraint area of the device should cover the entire lapping area, and the number of installation layers n is determined according to the project situation 2.2: Determine the height B of the device constraint module. The height is obtained according to the following formula; n(B + 4c) ≥ L s Specifically, the value range of B is: In the formula, n is the number of installation layers, B is the height of the restraint module, c is the concrete cover thickness of the concrete column, and L s is the lap length of the object to be strengthened; After determining the installation layer number n and the constraint module height B, perform a check calculation according to the following formula, and iterate repeatedly to obtain the optimal solution; nB / L s ≤0.55 2.3: Determine the width of the constraint module. The width w of the constraint module is determined according to the following formula; w ∈ [0.2a, 0.5a], a > 0 In the formula, a is the width of the concrete column. 2.4: Determine the thickness t of the constraint module. The thickness of the angle steel of the constraint module is determined according to the following formula; Where, σ s is the yield strength of the constraint module material, n is the number of device installation layers, and B is the height of the constraint module; F T is the tensile force on a single precision rolled threaded rod; The third step: Determine the dimensions of the connection module. 3.1: Determine the diameter of the threaded rod. Where, F l is the total lateral restraint force required for n sets of devices, n is the number of device layers, and F l / n is the required tensile force for each threaded rod on each set of devices, d is the diameter of the threaded rod, and σ b is the yield strength of the threaded rod material; 3.2: Determine the detailed dimensions of the connection module. The detailed dimensions of the connection module need to meet the following formula: In the formula, F l is the total lateral restraint force that needs to be applied to the n-layer device; β f is the increase coefficient of the strength design value of the fillet weld in the front; d1, b2, b3, h2 are the detailed dimensions of the connection module. Specifically: d1 is the diameter of the threaded hole, b1 is the thickness of the bottom plate of the connection module, b2 is the width of the connecting angle steel, b3 is the length of the connecting angle steel, h1 is the height of the connection module, and h2 is the height from the lower edge of the threaded hole to the lower bottom plate of the connecting angle steel; f f w is the strength design value of the fillet weld; The fourth step: Calculate the required torque. Wherein, μ' is the friction coefficient, which takes a value of 0.1 - 0.16 when the machining surface is a dry machining surface, and takes a value of 0.06 - 0.10 when the machining surface is a lubricated machining surface; L s is the existing lap length of the object to be strengthened; d b is the diameter of the longitudinal reinforcement of the object to be strengthened; A b is the cross-sectional area of the longitudinal reinforcement; f y is the design value / measured value of the yield strength of the longitudinal reinforcement; f c ′ is the compressive strength of the concrete of the concrete column; c is the concrete cover thickness; The fifth step: Install the device. 5.1: Clean the convex parts on the surface of the reinforcement position to ensure that the L-shaped corner contact angle steel (3) of the device fits tightly with the surface of the reinforcement object to obtain the best reinforcement effect; 5.2: Pass the high-strength threaded steel bar system (1) through the threaded hole (8) on the connecting angle steel (4), and install the displacement adjustment sleeve (6) and the high-strength bolt (5) on the outside of the high-strength threaded steel bar system (1). Connect the four groups of constraint modules of one layer of the device through the high-strength threaded steel bar system (1) at the specified positions. Use a wrench to turn the high-strength bolt (5), and apply the pre-tightening force in two stages: the first stage applies 20% of the target torque to each bolt to ensure that the device does not fall off due to gravity at the specified position; the second stage evenly applies torque to the four high-strength threaded steel bars. When the torques on the four high-strength threaded steel bars all reach the target torque, the device installation work can be completed.

2. The active restraint reinforcement method of threaded rod - angle steel for the reinforcement of square - section columns according to claim 1, wherein, In the step 2.1 described above, the value of n is 2 or 3.

3. The prestressed threaded rod - angle steel active constraint reinforcement method for a lapped and anchored defective column according to claim 1, characterized in that The number of the positioning sleeves (6) described above is determined according to the design method and actual situation.

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