Function-recoverable pier with built-in limiting device

Abstract

The invention provides a post-earthquake function recoverable pier structure with a built-in limiting device, the post-earthquake function recoverable pier structure comprises a concrete pier, a bearing platform, a longitudinal energy dissipation steel bar and the built-in limiting device, the limiting device is made of high-strength steel and is divided into an upper part and a lower part, the upper part and the lower part are respectively arranged at the bottom of the pier and the top of the bearing platform; when an earthquake acts, the horizontal displacement of the bridge pier enables the two parts to generate relative axial sliding, when the two parts slide by a certain distance, the buckles make contact, the bridge pier is limited to further generate horizontal displacement, residual displacement of the bridge pier is reduced, the bridge pier has certain reset capacity, and the original passing function of the bridge structure is recovered. The function-recoverable pier structure of the built-in limiting device meets the requirement of tough aseismic design, and has the reset capacity of resisting residual deformation. And under the condition of extremely strong earthquake, the problem that the bridge structure loses the original passing function due to collapse of the bridge pier caused by excessive residual displacement is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge structure earthquake resistance, and in particular to a reinforced concrete bridge pier structure with controllable damage and the ability to quickly restore traffic function after an earthquake. Background Art

[0002] As critical infrastructure in modern transportation networks, the seismic performance of bridges is crucial for ensuring smooth traffic flow, emergency rescue, and economic recovery after earthquakes. my country experiences frequent earthquake activity, and bridge piers, as core components that carry and stabilize bridges, are extremely vulnerable to damage. Severe damage can not only lead to the failure or collapse of the entire bridge, but also severely impact post-earthquake emergency access and the operation of regional transportation networks. Current bridge seismic design primarily employs a ductile design approach, dissipating earthquake energy through plastic deformation of piers. While this approach reduces the risk of structural collapse to a certain extent, it also introduces new challenges. For example, large residual deformations after an earthquake make it difficult to quickly restore bridge functionality, and most bridge structures require demolition and reconstruction, resulting in significant economic losses and resource waste. Furthermore, self-resetting pier technology, developed to address the shortcomings of traditional ductile design, while capable of some functional recovery, typically relies on prestressed tendons or external energy dissipation devices. This poses numerous challenges, including structural complexity, construction difficulties, significant cost increases, and limited energy dissipation capacity, hindering its widespread application in engineering projects.

[0003] As the concepts of resilient cities and sustainable development of infrastructure become more popular, the seismic design of bridges is gradually shifting from "structural safety" to "functional recovery", requiring bridges to not only not collapse during earthquakes but also to be able to quickly resume use after the earthquake. This places higher demands on the seismic performance of bridge piers, and the two major goals of "damage controllability" and "functional recoverability" must be achieved simultaneously. The former requires limiting the maximum displacement of bridge piers under earthquakes to prevent structural instability or even collapse; the latter emphasizes controlling residual deformation after an earthquake to ensure that the bridge can resume traffic within a short period of time. Therefore, there is an urgent need to develop a new type of bridge pier that combines the control of maximum residual deformation, economic feasibility, ease of construction, and efficient recovery capabilities, so as to achieve active control of residual deformation while ensuring energy dissipation capacity. Summary of the Invention

[0004] In response to the deficiencies in the above-mentioned prior art, the present invention provides a functionally restorable pier with a built-in limiting device, which solves the problems of the existing reinforced concrete piers, such as the difficult control of residual deformation, high maintenance cost, and limited functional restoration ability. The functionally restorable pier of the present invention has a simple structure, fully considering the concept of building a resilient city, and has the advantages of controllable damage, simple structure, low cost, and low maintenance cost. In the functionally restorable pier with a built-in limiting device of the present invention, the limiting device begins to work after the energy-absorbing longitudinal reinforcement of the pier yields, limiting the further residual displacement of the pier. It can effectively improve the structural stiffness and ensure that the limiting device gradually replaces the reinforcement to bear the force after the longitudinal energy-absorbing reinforcement of the pier yields, so as to avoid the collapse of the pier due to excessive residual deformation of the structure after the reinforcement is damaged.

[0005] In order to solve the technical problem of the present invention, a technical solution is proposed: a function-restoring bridge pier with a built-in limiting device, comprising a concrete bridge pier (1), a concrete cap (2), longitudinal energy-absorbing steel bars of the bridge pier (3), stirrups of the bridge pier (4), longitudinal steel bars of the cap (5), stirrups of the cap (6), and a limiting device (7), wherein the limiting device is divided into an upper part (8), a lower part (9), and a spacing between the limiting devices (10);

[0006] The reinforced concrete pier (1) body includes longitudinal energy-absorbing steel bars (3) and pier stirrups (4); the reinforced concrete cap (2) body includes longitudinal steel bars (5) and cap stirrups (6);

[0007] The upper portion (8) of the limiting device (7) is embedded in the bottom of the concrete pier (1);

[0008] The lower portion (9) of the limiting device (7) is embedded in the top of the concrete cap (2);

[0009] The limiting device (7) is made of high-strength steel and is bound to the inside of the pier together with the steel bars before the reinforced concrete pier is poured, with its upper part (8) located at the bottom of the pier and its lower part (9) located at the top of the pier cap;

[0010] The upper part (8) of the limiting device (7) is composed of a pull rod (11), a top nut (12), and a bottom nut (13), and the first top nut (12), the first bottom nut (13) and the pull rod are screwed in through threads and welded together; the lower part (9) of the limiting device (7) is composed of a sleeve (14), a second top nut (15), and a second bottom nut (16), and the second top nut (15), the second bottom nut (16) and the sleeve (14) are screwed in through threads and welded together; the first bottom nut (13) of the upper part (8) of the limiting device (7) and the second top nut (15) of the lower part (9) of the limiting device form a buckle and form a limiting device spacing (10).

[0011] Preferably, the length of the limiting device (7) needs to be greater than the length of the plastic hinge zone. The calculation formula of the plastic hinge zone is: Lp=0.1L-0.165h+7.32ds, where L is the net height of the concrete pier (1), h is the cross-sectional width of the concrete pier (1), and ds is the diameter of the longitudinal energy-absorbing steel bar (3) of the pier.

[0012] Preferably, the upper portion (8) and the lower portion (9) of the limiting device (7) need to come into contact and generate force after the longitudinal energy-absorbing steel bars (3) of the pier yield. The length setting of the limiting device spacing (10) between the upper and lower portions of the device is the key to regulating the residual displacement of the pier. Therefore, the size of the limiting device spacing (10) is determined according to the residual deformation size requirement of the pier. According to the results of the analysis of ordinary reinforced concrete piers, the plastic residual deformation of the concrete on the tensile side of the pier bottom is 1.5 mm, and thus the limiting device spacing (10) is determined to be 1 mm.

[0013] Preferably, when the limiting device (7) is processed, the surface of the steel material is sandblasted and coated with an anti-rust primer, the rod body of the device pull rod (11) is turned, and the sleeve (14) is cut from a seamless steel pipe; when the limiting device (7) is installed, a bracket is first welded on the base steel frame, and the assembled limiting device (7) is spot welded to the bracket. Before pouring concrete, the limiting device (7) is wrapped with a PE film to prevent concrete from penetrating into the sleeve (14).

[0014] Preferably, the limiting devices (7) are placed inside the pier in parallel with the longitudinal energy-absorbing steel bars (3) of the pier, with three being placed on each of the four sides of the 400mm×400mm cross-section pier, and the distance between each limiting device is 100mm.

[0015] Preferably, under a cyclic displacement load with an amplitude of ±1.5% of the pier height, the residual displacement rate of the pier ηres = δres / H × 100% ≤ 1%; where δres is the horizontal displacement value when the displacement loading node at the top of the pier is unloaded to zero load, and H is the height of the pier.

[0016] Beneficial effects of the present invention:

[0017] 1. The function of the built-in limiter in the present invention can restore the bridge pier and control the residual displacement of the pier compared with traditional reinforced concrete piers. The residual displacement rate of Example 1 is reduced by 33% compared with Comparative Example 1.

[0018] 2. The function of the built-in limit device of the present invention can restore the bridge pier. Compared with the traditional reinforced concrete bridge pier, the structural strength is high and it is not easy to collapse. The maximum load of the structure of Example 1 is increased by 13% compared with that of Comparative Example 1.

[0019] 3. The function of the built-in limiting device of the present invention can restore the bridge pier. Compared with the pier-cap separated self-resetting bridge pier with additional prestressed reinforcement proposed in the performance-based new self-resetting bridge pier anti-seismic theory and experimental research paper, the structural design is simple and the cost is lower.

[0020] 4. The material strength of the limit device of the present invention is greater than the strength of the longitudinal energy-absorbing steel bars of the pier, ensuring that the limit device can function normally after the longitudinal bars yield.

[0021] 5. The function of the built-in limiting device of the present invention can be restored. The bridge pier is an extension of the traditional reinforced concrete bridge pier structure. There is no need to install complex components, and the construction is convenient.

[0022] 6. Compared with existing reinforced concrete bridge piers, the present invention demonstrates significant benefits. The functionally resilient piers with built-in limiters address existing reinforced concrete piers' issues of difficult-to-control residual deformation, high maintenance costs, and limited functional recovery, thereby improving bearing capacity. In these resilient piers, the longitudinal energy-absorbing steel bars and the limiters operate sequentially, effectively controlling the pier's residual displacement and ensuring its functional recoverability.

[0023] 7. Comparative Example 1 demonstrates the importance and necessity of adding limiters. Adding limiters is a prerequisite for limiting residual displacement of bridge piers and improving seismic performance. In Example 1, the limiters are constructed using steel of higher strength than the longitudinal reinforcement to ensure that the longitudinal reinforcement yields before the limiters, ensuring that the limiters fully function to control residual deformation. In terms of studying the seismic performance of bridge piers, Example 1 optimizes and improves Comparative Example 1.

[0024] 8. The present invention relates to the field of seismic resistance for engineering structures and provides a post-earthquake restorable pier structure with a built-in limiter to address the existing problem of controlling excessive residual deformation of pier columns. This post-earthquake restorable pier structure comprises a concrete pier and abutment, longitudinal energy-absorbing steel bars, and a built-in limiter. The limiter is constructed of high-strength steel and consists of two parts, upper and lower, located at the bottom of the pier and top of the abutment, respectively. A latch is formed between the upper and lower parts of the limiter. During an earthquake, the horizontal displacement of the pier causes the two parts to slide axially relative to each other. After sliding a certain distance, the latch contacts, limiting further horizontal displacement of the pier, reducing the residual displacement and providing a certain degree of restorability, allowing the bridge structure to resume its original function. The present invention's restorable pier structure with a built-in limiter meets the design requirements for toughness and has the ability to resist residual deformation. In the event of an extremely strong earthquake, this solves the problem of pier collapse due to excessive residual displacement, which can cause the bridge structure to lose its original function. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] Figure 1 This is a schematic diagram of the overall structure of the bridge pier that can be restored by using the function of the built-in limiting device of the present invention (the outer periphery of the limiting device is hidden by concrete).

[0027] Figure 2 It is a schematic diagram of the front elevation of a bridge pier that can be restored by using the function of the built-in limiting device of the present invention.

[0028] Figure 3 It is a schematic front elevation view of a limiting device in a bridge pier that can restore the function of the built-in limiting device of the present invention.

[0029] Figure 4 1 is a comparison diagram of the hysteresis curves of Example 1 and Comparative Example 1.

[0030] 1-concrete pier; 2-concrete cap; 3-longitudinal energy-absorbing steel bars of pier; 4-stirrups of pier; 5-longitudinal steel bars of cap; 6-stirrups of cap; 7-limiting device; 8-upper part; 9-lower part; 10-spacing of limiting device; 11-pull rod; 12-first top nut; 13-first bottom nut; 14-sleeve; 15-second top nut; 16-second bottom nut. DETAILED DESCRIPTION

[0031] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1-Figure 3 As shown, a built-in limiting device can restore the function of a bridge pier, including a concrete pier 1, a concrete cap 2, pier longitudinal energy-absorbing steel bars 3, pier stirrups 4, cap longitudinal steel bars 5, pier stirrups 6, and a limiting device 7. The limiting device is divided into an upper portion 8, a lower portion 9, and a limiting device spacing 10. The reinforced concrete pier 1 body includes the pier longitudinal energy-absorbing steel bars 3 and the pier stirrups 4; the reinforced concrete cap 2 body includes the cap longitudinal steel bars 5 and the cap stirrups 6.

[0034] The upper portion 8 of the limiting device 7 is embedded in the bottom of the concrete pier 1;

[0035] The lower portion 9 of the limiting device 7 is embedded in the top of the concrete cap 2;

[0036] The limiter 7 is made of high-strength steel and is bound to the inside of the pier together with the steel bars before the reinforced concrete pier is poured, with its upper part 8 located at the bottom of the pier and the lower part 9 located at the top of the cap.

[0037] The upper part 8 of the limiting device 7 is composed of a pull rod 11, a top nut 12, and a bottom nut 13. The first top nut 12, the first bottom nut 13 and the pull rod are screwed in through threads and welded together; the lower part 9 of the limiting device 7 is composed of a sleeve 14, a second top nut 15, and a second bottom nut 16. The second top nut 15, the second bottom nut 16 and the sleeve 14 are screwed in through threads and welded together; the first bottom nut 13 of the upper part 8 of the limiting device 7 and the second top nut 15 of the lower part 9 of the limiting device form a snap and form a limiting device spacing 10.

[0038] The pier components measure 400mm x 400mm x 1700mm, and the abutment components measure 1400mm x 900mm x 500mm. The concrete specification for the pier abutment is C30, and the longitudinal energy-absorbing reinforcement bars 3 are HRB335, with 16 bars of 12mm in diameter. The stirrups 4 are HRB335, with 6 bars of 50mm in diameter. The longitudinal reinforcement bars 5 and stirrups 6 are HRB335, with 16 bars of 16mm in diameter and 6 bars of 150mm in diameter. According to the plastic hinge zone calculation formula: Lp = 0.1L - 0.165h + 7.32ds, where L is the clear height of the pier, h is the cross-sectional width of the pier, and ds is the diameter of the longitudinal energy-absorbing reinforcement bars 3 in the pier, the plastic hinge zone length of the pier in Example 1 is 191mm, which is used to design the limiter length. The pull rod 11 of the upper part 8 of the limiting device has a diameter of 20 mm and a length of 240 mm, which is larger than the length of the plastic hinge zone; the first top nut 12 has a diameter of 30 mm and a length of 20 mm; the first bottom nut 13 has a diameter of 25 mm and a height of 20 mm. The sleeve 14 of the lower part 9 of the limiting device has a diameter of 30 mm and a length of 130 mm; the second top nut 15 and the second bottom nut 16 have a diameter of 30 mm and a length of 20 mm. The limiting device 7 is made of Q420 high-strength steel. In order to ensure that the pull rod 11 and the first bottom nut 13 can be assembled, the outer diameter of the pull rod 11 is 20 mm, the inner diameter of the first bottom nut 12 is 21 mm; the opening size of the second top nut 15 is 20.5 mm, ensuring that the pull rod 11 can pass freely without getting stuck. When installing the upper part 8 and the lower part 9 of the limit device, make the pull rod 11 pass vertically through the inner hole of the second top nut 15, screw the first top nut 12 and the first bottom nut 13 into the pull rod 11 to the reserved welding section, and do the same with the second top nut 15, the second bottom nut 16 and the sleeve 14 to ensure the accuracy of the thread fit; then perform circumferential welding on the nut-rod body / sleeve joint (weld height ≥ 3mm), grind off the spatter after welding to ensure permanent locking of the threaded connection; finally, form a buckle composed of the first bottom nut 13 and the second top nut 15, so that the limit device 7 can slide axially and cannot be separated. Note: Welding is performed immediately after screwing in. During assembly, the components have been welded into a whole, and the buckle connection is completed only by axial sleeve connection.

[0039] When processing the limiting device 7, the steel surface is sandblasted and coated with anti-rust primer. The rod body of the device pull rod 11 is turned, and the sleeve 14 is cut from a seamless steel pipe. When installing the limiting device 7, the bracket is first welded on the base steel frame, and the assembled limiting device 7 is spot welded to the bracket. Before pouring concrete, the limiting device 7 is wrapped with PE film to prevent concrete from penetrating into the sleeve 14.

[0040] The upper and lower portions 8 and 9 of the stopper 7 must contact and generate force after the longitudinal energy-absorbing reinforcement 3 of the pier yields. The length of the spacing 10 between the upper and lower portions of the stopper is crucial for controlling the residual displacement of the pier. Therefore, the size of the spacing 10 is determined based on the required residual deformation of the pier. Based on the analytical results of conventional reinforced concrete piers, which show a plastic residual deformation of 1.5 mm on the tensile side of the pier bottom, the spacing 10 is set to 1 mm.

[0041] The limiting devices 7 are placed inside the pier in parallel with the longitudinal energy-absorbing steel bars 3 , with three placed on each of the four sides of the 400mm×400mm cross-section pier, and the distance between each limiting device is 100mm.

[0042] In order to verify that the function of the built-in limiting device of the present invention can restore the seismic performance of the bridge pier, a finite element simulation of Example 1 was performed using MIADS FEA NX software.

[0043] Model construction:

[0044] Geometric model: Based on the function of the built-in limiting device of Example 1, a three-dimensional solid model of the bridge pier (pier height 1.7m, cross-section 400mm×400mm) can be restored, including the abutment, the pier body, the steel grid and the limiting device (split structure).

[0045] Material Definition:

[0046] Concrete: A smeared crack constitutive model was used, with concrete strength grade C30, elastic modulus of 30 GPa, and Poisson's ratio of 0.2. For nonlinear analysis, the Hordijk function was used for the tensile function, with an Ft input of 2.01 MPa and a fracture energy Gf input of 0.12 N / mm2. The Nakamura function was used for the compression function, with an Fc input of 20.1 MPa. The shear function was automatically generated by the software.

[0047] Reinforcement: Longitudinal reinforcement HRB335 adopts Menegotto-Pinto model, elastic modulus 20.6MPa, yield strength fy input 335MPa, hardening ratio 0.01;

[0048] Limit device: The high-strength steel adopts the Van Messiers ideal plasticity model, and the yield strength input is 420MPa.

[0049] Unit division:

[0050] Hexahedral solid elements are used for concrete, and the mesh size increases linearly from 50 mm in the key research area (around the limit device) to 100 mm in the non-key research area;

[0051] The reinforcement adopts embedded truss elements and is automatically coupled with the concrete.

[0052] Contact elements and boundary conditions:

[0053] Contact setting: a bidirectional sliding contact unit is set between the sliding surfaces connecting the upper and lower parts of the limit device; a general contact unit is set on the contact surfaces at both ends of the gap between the upper and lower parts of the device; a welding contact unit is set on the outer surface of the limit device cast in concrete and the contact surface with the concrete.

[0054] Boundary constraints:

[0055] The bottom surface of the pedestal is fully constrained;

[0056] A horizontal displacement load point is applied on the top of the pier to constrain the direction of displacement.

[0057] Loading conditions:

[0058] A horizontal displacement load of 35 mm is applied to the displacement loading point on the top of the pier.

[0059] Quasi-static analysis: Cyclic reciprocating loads controlled by horizontal displacement are applied to the top of the pier;

[0060] Loading protocol: increasing by displacement amplitude (5 mm per level);

[0061] Loading rate: quasi-static (1 mm / step).

[0062] Finite element analysis results were analyzed to collect data on load and displacement at the pier loading location, contact force of the limiter, concrete strain at the pier bottom, and stress in the longitudinal reinforcement. The primary failure mode of the pier during the initial loading phase was concrete cracking, which spread from the bottom of the pier toward the top. The most common cracks occurred in areas with high bending moments. The longitudinal reinforcement at the pier bottom reached a yield strength of 335 MPa when the horizontal displacement reached approximately 14 mm. The maximum load at the pier loading location was 88.29 kN, with a horizontal displacement of 35 mm. (See [1] for details.) Figure 4 , all the longitudinal reinforcements at the bottom of the pier enter the yield state, and the horizontal stiffness of the model is close to 0. The limit device comes into contact when the horizontal displacement of the pier reaches 17mm. When the horizontal displacement is 35mm, the maximum contact force of a single device reaches 61800N. The function of the built-in limit device of the present invention can restore the pier. After the reinforcement reaches yield, the limit device comes into contact and generates contact force to constrain the pier to further residual displacement. After the reinforcement yields, the model stiffness gradually flattens. After the limit device comes into contact, the horizontal stiffness of the model increases significantly. When the horizontal displacement of the loading position reaches 30mm, the maximum load at the loading position of the pier reaches a maximum value of 91.79kN, after which the horizontal stiffness of the model gradually flattens. The horizontal displacement of the displacement action node at the top of the pier at the end of unloading is extracted, and the displacement value of the x-axis intersection when unloading from the peak load point to zero load at this moment is used as the residual displacement.

[0063] The results of Example 1 show that the residual displacement of the pier under the displacement amplitude of ±1.5%H must satisfy ηres=δres / H×100%≤1%. (wherein δres is the displacement value when the displacement loading node at the top of the pier is unloaded to zero load, and H is the height of the pier). The residual displacement rate of Example 1 is only 0.8%, and the maximum load of the pier is 88.29KN. This shows that the function of the built-in limit device of the present invention can restore the pier, effectively improving the structural stiffness. After the longitudinal energy-absorbing steel bars of the pier yield, the limit device gradually replaces the steel bars to bear the force, so as to avoid excessive residual deformation of the structure after the steel bars are damaged, which may lead to the collapse of the pier. It is verified that the function of the built-in limit device of the present invention can restore the pier and control the residual displacement of the pier.

[0064] Comparative Example 1

[0065] In order to prove the function of the built-in limiting device of the present invention in restoring the importance of the bridge pier and highlight its effect, comparative example 1 was implemented.

[0066] In Comparative Example 1, no internal limiting devices are incorporated into the piers and abutments, unlike in Example 1. Aside from the limiting devices, all other parameters in Comparative Example 1 are identical to those in Example 1: the pier components measure 400mm x 400mm x 1700mm, and the abutment components measure 1400mm x 900mm x 500mm. The pier abutment concrete is constructed of C30, the longitudinal energy-absorbing steel bars are constructed of HRB335, and the number of bars is 16 φ12. The stirrups are constructed of HRB335, and the number of stirrups is φ6@50. The longitudinal steel and stirrups in the abutment are constructed of HRB335, with 16 φ16 longitudinal bars and φ6@150 stirrups. To focus on the impact of internal limiting devices on the seismic performance of the piers, Comparative Example 1 employs the same constraints and loading methods as in Example 1.

[0067] In Comparative Example 1, a finite element model of a bridge pier cap having the same dimensions and material parameters as those of Example 1 was produced.

[0068] Model construction:

[0069] Geometric model: A three-dimensional solid model was established based on the ordinary reinforced concrete bridge pier (1.7m high, 400mm×400mm cross-section) of Comparative Example 1, including the abutment, pier body, and steel grid.

[0070] Material Definition:

[0071] Concrete: A smeared crack constitutive model was used, with concrete strength grade C30, elastic modulus of 30 GPa, and Poisson's ratio of 0.2. For nonlinear analysis, the Hordijk function was used for the tensile function, with an Ft input of 2.01 MPa and a fracture energy Gf input of 0.12 N / mm2. The Nakamura function was used for the compression function, with an Fc input of 20.1 MPa. The shear function was automatically generated by the software.

[0072] Reinforcement: Longitudinal reinforcement HRB335 adopts Menegotto-Pinto model, elastic modulus 20.6MPa, yield strength fy input 335MPa, hardening ratio 0.01;

[0073] Unit division:

[0074] Hexahedral solid elements are used for concrete, and the mesh size increases linearly from 50 mm in the key research area (around the limit device) to 100 mm in the non-key research area;

[0075] The reinforcement adopts embedded truss elements and is automatically coupled with the concrete.

[0076] Boundary conditions:

[0077] Boundary constraints:

[0078] The bottom surface of the pedestal is fully constrained;

[0079] A horizontal displacement load point is applied on the top of the pier to constrain the direction of displacement.

[0080] Loading conditions:

[0081] A horizontal displacement load of 35 mm is applied to the displacement loading point on the top of the pier.

[0082] Quasi-static analysis: Cyclic reciprocating loads controlled by horizontal displacement are applied to the top of the pier;

[0083] Loading protocol: increasing by displacement amplitude (5 mm per level);

[0084] Loading rate: quasi-static (1 mm / step).

[0085] Analyze the results of the finite element analysis and collect data such as the load and displacement at the pier loading position, the concrete strain at the pier bottom, and the stress of the longitudinal reinforcement. The main failure mode of the pier in the initial loading period is concrete cracking, which extends from the bottom of the pier to the top of the pier. The locations with more cracks are where the bending moment is greater. As in Example 1, the longitudinal reinforcement at the bottom of the pier reaches a yield strength of 335MPa when the horizontal displacement is loaded to about 14mm. When the horizontal displacement of the loading position reaches 20mm, the load reaches a maximum value of 77.91kN. Figure 4At this point, the longitudinal reinforcement at the bottom of the pier almost all enters the yield state, and the horizontal stiffness of the model is close to 0. The horizontal displacement of the displacement action node at the top of the pier at the end of unloading is extracted, and the displacement value of the x-axis intersection when unloading from the load peak point to zero load at this moment is taken as the residual displacement.

[0086] The results of Comparative Example 1 show that at a displacement amplitude of ±1.5%H, the residual displacement rate is 1.2%. In Example 1, the maximum pier load is 88.29 kN, while in Comparative Example 1, the maximum load is 77.91 kN, a 13% increase compared to Comparative Example 1. The residual displacement rate is 0.8%, a 33% decrease compared to Comparative Example 1. The difference in residual displacement between the two examples increases with increasing horizontal displacement of the loading point. This demonstrates that the function of the built-in limiter in the present invention can restore the pier, increasing its bearing capacity while also reducing its residual displacement.

[0087] Through comparative example 1, it is verified that the function of the built-in limiting device of the present invention can restore the importance and necessity of the bridge pier. The built-in limiting device in the bridge pier can improve the bearing capacity of the bridge pier and reduce the residual displacement of the bridge pier, thereby effectively improving the seismic performance of the bridge pier.

Claims

1. A function-recoverable bridge pier with a built-in limit device, characterized in that: The invention comprises a concrete bridge pier (1), a concrete cap (2), a bridge pier longitudinal energy-absorbing steel bar (3), a bridge pier stirrup (4), a cap longitudinal steel bar (5), a cap stirrup (6), and a limit device (7), wherein the limit device is divided into an upper part (8), a lower part (9), and a distance between the limit devices (10); The reinforced concrete pier (1) body includes longitudinal energy-absorbing steel bars (3) and pier stirrups (4); the reinforced concrete cap (2) body includes longitudinal steel bars (5) and cap stirrups (6); The upper portion (8) of the limiting device (7) is embedded in the bottom of the concrete pier (1); The lower portion (9) of the limiting device (7) is embedded in the top of the concrete cap (2); The limiting device (7) is made of high-strength steel and is bound to the interior of the reinforced concrete pier (1) together with the steel bars before the reinforced concrete pier (1) is poured, with its upper portion (8) located at the bottom of the concrete pier (1) and its lower portion (9) located at the top of the concrete cap (2); The upper part (8) of the limiting device (7) is composed of a pull rod (11), a first top nut (12), and a first bottom nut (13), and the first top nut (12), the first bottom nut (13) and the pull rod (11) are screwed in through threads and welded together; the lower part (9) of the limiting device (7) is composed of a sleeve (14), a second top nut (15), and a second bottom nut (16), and the second top nut (15), the second bottom nut (16) and the sleeve (14) are screwed in through threads and welded together; the first bottom nut (13) of the upper part (8) of the limiting device (7) and the second top nut (15) of the lower part (9) of the limiting device (7) form a buckle and form a limiting device spacing (10).

2. The function of the bridge pier with built-in limiting device according to claim 1 can be restored, characterized in that: The length of all the limiting devices (7) must be greater than the length of the plastic hinge zone. The calculation formula of the plastic hinge zone is: Lp = 0.1L-0.165h+7.32ds, where L is the net height of the concrete pier (1), h is the cross-sectional width of the concrete pier (1), and ds is the diameter of the longitudinal energy-absorbing steel bar (3) of the pier.

3. The function of the bridge pier with built-in limiting device according to claim 1 can be restored, characterized in that: The upper part (8) and the lower part (9) of the limiting device (7) need to come into contact and generate resistance after the longitudinal energy-absorbing steel bars (3) of the pier yield. The length setting of the limiting device spacing (10) between the upper and lower parts of the device is the key to regulating the residual displacement of the pier. Therefore, the size of the limiting device spacing (10) is determined according to the residual deformation size requirement of the pier. According to the analysis results of ordinary reinforced concrete piers, the plastic residual deformation of the tensile side concrete at the bottom of the pier is 1.5 mm, and thus the limiting device spacing (10) is determined to be 1 mm.

4. The function of the bridge pier with built-in limiting device according to claim 1 can be restored, characterized in that: When the limiting device (7) is processed, the steel surface is sandblasted and coated with anti-rust primer, the rod body of the pull rod (11) is processed by a turning processing device, and the sleeve (14) is cut from a seamless steel pipe; when the limiting device (7) is installed, a bracket is first welded on the longitudinal steel bar (5) skeleton of the base, and the assembled limiting device (7) is spot welded to the bracket. Before pouring concrete, the limiting device (7) is wrapped with a PE film to prevent concrete from penetrating into the sleeve (14).

5. The function of the bridge pier with built-in limiting device according to claim 1 can be restored, characterized in that: The limiting devices (7) are placed inside the pier in parallel with the longitudinal energy-absorbing steel bars (3) of the pier, and three are placed on each of the four sides of the 400mm×400mm cross-section pier, with the distance between each limiting device being 100mm.

6. The function of the bridge pier with built-in limiting device according to claim 1 can be restored, characterized in that: Under a cyclic load with an amplitude displacement of ±1.5% of the pier height, the residual displacement rate of the pier is ηres = δres / H × 100% ≤ 1%; where δres is the horizontal displacement value of the displacement loading node at the top of the pier when it is unloaded to zero load, and H is the pier height.

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