Friction swing type pier capable of resetting after collision

Abstract

The invention discloses a friction pendulum type pier capable of resetting after collision, and belongs to the technical field of improvement of anti-collision toughness of swinging piers, linear unbonded prestressed steel strands are arranged in the pier in a full-length mode, the pier bottom of the pier is in friction pendulum type interface contact with a foundation platform, and the pier bottom of the pier is connected with the foundation platform through an external energy dissipater. The prestressed steel strands are arranged in a manner of penetrating through the pier body by adopting a post-tensioning process to form a longitudinal pre-pressure field, and the prestressed steel strands and the whole pier are subjected to unbonded treatment. The friction pendulum type interface is adopted at the pier bottom of the pier to replace a traditional plane interface, large displacement can be generated under the action of impact loads, most energy is absorbed through the external energy dissipater, damage to the pier is effectively reduced, restoring force is provided through the prestress steel strand and structural gravity, residual displacement of the pier is reduced, and the service life of the pier is prolonged. And the anti-collision performance and the function restorability of the swing bridge in the service period are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of improving the anti-collision toughness of a rocking pier, and particularly relates to a post-impact resettable friction pendulum type pier and a construction method. BACKGROUND

[0002] With the popularization of the concept of seismic toughness design, rocking bridges, as a new type of seismic structure, not only can achieve the design goal of "not falling in a major earthquake", but also can quickly restore traffic function after the earthquake, significantly improving the seismic performance and repairability of the bridge, and becoming an important progress in the seismic technology of bridges in China. Rocking bridges can effectively dissipate seismic energy and reduce structural damage by allowing controllable rotation between the pier body and the foundation, thereby achieving rapid recovery of function after the earthquake. However, in addition to bearing seismic loads, rocking bridges may also face extreme actions such as vehicle impact and rock impact in actual use. These impact loads have characteristics such as large amplitude, short action time, and significant local effect, which can cause spatial dislocation of the rocking interface and even overall instability, thereby losing the controllability of bridge damage and the recoverability of function, and failing to achieve the anti-collapse and rapid function recovery goals under impact action.

[0003] Currently, the design of rocking bridges mainly targets seismic loads, and the rocking interface of the pier is usually arranged in a planar manner. This arrangement can effectively provide restoring force through the opening and closing of the interface and the stretching and compression of the energy dissipation device under seismic loads, but has obvious deficiencies under impact loads. Impact action is mainly represented by shear loads, so the planar arrangement is difficult to adapt to the complex deformation caused by impact, and cannot provide sufficient equivalent restoring force to achieve post-impact resetting, resulting in reduced controllability of the rocking interface and affecting the overall safety and function recovery capability of the bridge.

[0004] Therefore, the present application proposes an innovative post-impact resettable friction pendulum type pier and a construction method. By using a friction pendulum type interface instead of a traditional planar interface, uniform distribution of axial pressure can be provided under impact loads, effectively adapting to the spatial dislocation and complex deformation of the rocking interface, and improving the anti-impact performance and function recoverability of the rocking bridge during the service period. SUMMARY

[0005] Therefore, the present application aims to provide a post-impact resettable friction pendulum type pier, especially for rocking bridges, which can provide greater elastic restoring force in pier impact damage, has excellent shear resistance and does not affect the bending resistance of the pier, while maintaining the anti-cracking and bending performance similar to the widely used planar interface rocking pier, and greatly improving the pier resetting function.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The application provides a post-collision resettable friction pendulum type bridge pier, which comprises, from top to bottom, a pier top cover beam, a pier body and a foundation slab, a prestressed steel strand in a linear shape is embedded in the bridge pier, the prestressed steel strand is arranged at the center of the cross section of the bridge pier, the prestressed steel strand is arranged through the pier body by using a post-tensioning process to form a longitudinal pre-compression stress field, the pier body and the foundation slab are connected by using an external energy dissipation device, the prestressed steel strand and the bridge pier are not bonded to adapt to the controllable rotation of the pier body, the two ends of the prestressed steel strand are anchored on anchor plates in the pier top cover beam and the foundation slab respectively, and the prestressed steel strand is subjected to pre-tightening force by using an over-tensioning process, a sliding spherical surface is arranged on the foundation slab, the pier body is arranged on the foundation slab, and the center of the sliding spherical surface coincides with the connecting point of the pier body and the pier top cover beam.

[0007] Further, arc-shaped steel plates are fixedly arranged on the foundation slab, two arc-shaped steel plates are symmetrically arranged on opposite sides of the sliding spherical surface, anchor plates are fixedly connected to opposite side walls of the pier body, and energy dissipation devices are fixedly connected between the anchor plates and the arc-shaped steel plates.

[0008] Further, an adjustable anchor plate is arranged at the top end of the pier top cover beam, a guide hole corresponding to the prestressed steel strand is arranged on the adjustable anchor plate, and a wear-resistant nylon bushing is arranged on the inner wall of the guide hole.

[0009] Further, the construction method of the post-collision resettable friction pendulum type bridge pier comprises the following steps. S1: during the concrete pouring stage of the foundation slab and the pier body, a PCV pipe is used to reserve a 50mm-diameter hole in the foundation slab, and an energy dissipation device is fixedly connected between the arc-shaped steel plate and the anchor plate; S2: after the pier top cover beam and the pier body are connected, an intelligent tensioning system is used to implement staged tensioning: first, 10% of pre-tightening force is applied to eliminate the gap between the steel strands, and then formal tensioning is performed: the pre-tightening force is loaded in three stages to 105%, each stage is held for 5 minutes, and then the pre-tightening force is reduced to 100% after over-tensioning, and finally, the pre-tightening force is locked. is the designed tensioning control stress.

[0010] The application has the following beneficial effects: By using a friction pendulum type interface at the bottom of the bridge pier to replace a traditional plane interface, the application can generate a large displacement under the action of impact load, can absorb most of the energy by using an external energy dissipation device, can effectively reduce the damage of the bridge pier, can reduce the residual displacement of the bridge pier by using the prestressed steel strand and the gravity of the structure to provide restoring force, and can improve the anti-collision performance and functional recoverability of the swing bridge during the service period.

[0011] ​​​Additional advantages, objects, and features of the application will be set forth in part by the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or can be learned from practice of the application. The objects and other advantages of the application can be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0012] To make the objectives, technical solutions and beneficial effects of the present application clearer, the present application is described below with the help of the following drawings: Figure 1 It is a schematic diagram of prestressed tendon arrangement structure of the embodiment of the present application; Figure 2 It is a schematic diagram of prestressed tendon arrangement model of the embodiment of the present application; Figure 3 It is a restoring force model of a plane interface pier; Figure 4 It is a restoring force model of the embodiment of the present application; Figure 5 It is a schematic diagram of left swing of a pier bottom of a plane interface swing pier; Figure 6 It is a schematic diagram of right swing of a pier bottom of a plane interface swing pier; Figure 7 It is a schematic diagram of left swing of a pier bottom of a post-impact resettable friction pendulum type pier of the embodiment of the present application; Figure 8 It is a schematic diagram of right swing of a pier bottom of a post-impact resettable friction pendulum type pier of the embodiment of the present application; Figure 9 It is a prestress time history curve diagram of a pier bottom of a plane interface swing pier and a post-impact resettable friction pendulum type pier under impact load; Figure 10 It is a curve diagram of pier bottom displacement changing with time of a plane interface swing pier and a post-impact resettable friction pendulum type pier under impact load.

[0013] In the drawings, the following marks are used: foundation pile cap 1, pier body 2, pier top cap beam 3, prestressed steel strand 4, sliding spherical surface 5, external energy dissipater 6, arc-shaped steel plate 7, anchoring plate 8, adjustable anchoring plate 9. DETAILED DESCRIPTION

[0014] As Figures 1-10As shown, this invention provides a post-impact reversible friction pendulum pier, comprising a pier cap beam 3, a pier body 2, and a foundation cap 1, which are fixedly connected from top to bottom. A prestressed steel strand 4, arranged in a straight line, is pre-embedded within the pier and positioned at the center of the pier's cross-section. The prestressed steel strand 4 is installed through the pier body 2 using a post-tensioning process to form a longitudinal prestress field. The pier body 2 and the foundation cap 1 are connected by an external energy dissipator 6. The prestressed steel strand 4 and the pier are treated without bonding to accommodate the controllable rotation of the pier body 2. Both ends of the prestressed steel strand 4 are anchored to anchor plates in the pier cap beam 3 and the foundation cap 1, respectively, and a prestressing force is applied to the prestressed steel strand 4 using an over-tensioning process. A sliding spherical surface 5 is provided on the foundation cap 1, and the pier body 2 is slidably mounted on the sliding spherical surface 5. The center of the sliding spherical surface 5 coincides with the connection point between the pier body 2 and the pier cap beam 3.

[0015] Among them, an arc-shaped steel plate 7 is fixedly installed on the foundation platform 1, and two arc-shaped steel plates 7 are symmetrically arranged on opposite sides of the sliding spherical surface 5. Anchor plates 8 are fixedly connected to the opposite side walls of the pier body 2, and an energy dissipator 6 is fixedly connected between the anchor plate 8 and the arc-shaped steel plate 7. An adjustable anchor plate 9 is provided at the top of the pier cap beam 3. The adjustable anchor plate 9 is provided with guide holes corresponding to the prestressed steel strands 4. The inner wall of the guide holes is provided with wear-resistant nylon bushings.

[0016] The construction method includes the following steps: S1: During the concrete pouring stage of the foundation cap 1 and the pier body 2, the foundation cap 1 uses PVC pipe to reserve a 50mm diameter channel, and the energy dissipator 6 is fixedly connected between the arc-shaped steel plate 7 and the anchor plate 8. The arc-shaped steel plate 7 is provided with steel bars anchored in the foundation cap 1 and connected to the energy dissipator 6 through pre-embedded screws. S2: After connecting the pier cap beam 3 to the pier body 2, a staged tensioning system is used to implement tensioning: first apply 10%... Pre-tensioning to eliminate gaps in the steel strands; formal tensioning: applied in three stages to 105%. After each load level is held for 5 minutes, the tension is reduced to 100%. Locked; among which, To design the tension control stress.

[0017] Regarding this invention, the prestressing time history curves and pier bottom displacement curves of a conventional planar bridge pier and the post-impact restorable friction pendulum bridge pier of this invention are simulated and compared under impact loads. Figure 9 — Figure 10 ; Ordinary planar bridge piers: (1) Axial resultant force N : The pier is tilted on one side and contacts on the other side at point O. The coordinate along the contact width is assumed to be x , the pressure can be approximated as a triangular linear distribution: The bending moment caused by the uneven pressure distribution: The point of action of the resultant force is at , the total width of the rectangular base plate is b , and the eccentricity relative to the center of the cross section is The additional bending moment caused by the eccentricity of the axial force: For a rectangular cross-section with eccentric axial force, in order to ensure that the entire cross-section is free of cracking / seam, the eccentricity must satisfy: Substituting we get ， That is, only when the entire cross-section is in contact does the eccentricity condition hold; when the contact width is less than the base plate width , the eccentricity will exceed , indicating that once partial contact occurs, the axial pressure will necessarily be unevenly distributed and significantly eccentric.

[0018] (2) According to the balance of forces: where is the impact force, is the axial resultant force, is the prestressed steel strand force, is the energy dissipation force, is the bridge pier gravity, is the height of the foundation slab 1, is the initial height of the impact force from the top surface of the foundation slab 1, is the initial height of the prestressed steel strand from the bottom surface of the foundation slab 1, is the initial height of the energy dissipation from the top surface of the foundation slab 1, is the rotation angle, is the angle between and the horizontal direction, is the angle between and the horizontal direction, is the horizontal displacement of the point of action of the gravity from point O, is the moment of inertia of the bridge pier, is the angular acceleration of the bridge pier, I represents the moment of inertia, which represents the contribution of the inertial force to rotation.

[0019] Although the total vertical force is constant, the contact width c changes continuously with the pier angle, and the resultant point deviates from the center of the section, resulting in uneven axial pressure, which cannot effectively disperse energy and is prone to cause local damage and residual displacement.

[0020] Post-crash resettable friction pendulum pier: (1) Loading process According to the balance of forces, take the distance from the center: (2) Unloading process Assume that the position of the restoring force is still at the loading point position: For this system, when the system rotates counterclockwise, the angle is positive, and , the force formula at the impact point is: When the system is subjected to dynamic action: Introducing to evaluate the contribution of the inertial force to the shear force on the pier.

[0021] In the formula, is the impact force, is the prestressed steel strand force, is the energy dissipation force, D is the horizontal displacement of the pier bottom, is the gravity of the pier, R is the pier height (rotational radius), is the initial height of the impact force from the arc bottom surface, is the initial height from the arc bottom surface, is the rotation angle, is the angle with the horizontal direction, is the angle with the horizontal direction, is the friction coefficient, is the moment of inertia of the pier, is the angular acceleration of the pier, I represents the moment of inertia, which represents the contribution of the inertial force to rotation.

[0022] The post-crash resettable friction pendulum pier realizes double optimization through the arc interface, has excellent shear performance and does not affect the pier's bending and cracking resistance, such as Figures 7-8, Based on LS-DYNA platform, the simulation comparison found that the rotation of the post-crash reset friction pendulum type pier always keeps a relatively symmetrical contact state with the arc contact interface, and the normal pressure is uniformly distributed along the contact surface under the impact load without eccentric contact . Therefore, uniform distribution of axial pressure can be provided, and energy can be effectively dispersed to reduce local damage and adapt to spatial dislocation and complex deformation of the rocking interface; the anti-seismic performance is not affected, the anti-shear impact performance is good, the residual displacement is low, and the pier reset capability after impact is significantly improved compared with the pier with a planar interface.

[0023] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A post-impact reversible friction pendulum pier, comprising: The bridge structure consists of a pier cap beam, pier body, and foundation cap, which are fixedly connected sequentially from top to bottom. The key feature is that a prestressed steel strand is pre-embedded in the pier in a straight line at the center of the pier's cross-section. The prestressed steel strand is installed through the pier body using a post-tensioning process to form a longitudinal prestress field. The pier body and foundation cap are connected by an external energy dissipator. The prestressed steel strand and pier are treated without bonding to accommodate the controllable rotation of the pier body. Both ends of the prestressed steel strand are anchored to anchor plates in the pier cap beam and foundation cap, respectively. Prestressing is applied to the prestressed steel strand using an over-tensioning process. A sliding spherical surface is provided on the foundation cap, and the pier body is located on the foundation cap. The center of the sliding spherical surface coincides with the connection point between the pier body and the pier cap beam.

2. The impact-recoverable friction pendulum pier according to claim 1, characterized in that: An arc-shaped steel plate is fixedly installed on the foundation platform. Two arc-shaped steel plates are symmetrically arranged on opposite sides of the sliding spherical surface. Anchor plates are fixedly connected to the opposite side walls of the pier body. Energy dissipators are fixedly connected between the anchor plates and the arc-shaped steel plates.

3. The impact-recoverable friction pendulum pier according to claim 1, characterized in that: An adjustable anchor plate is provided at the top of the pier cap beam. The adjustable anchor plate is provided with guide holes corresponding to the prestressed steel strands. The inner wall of the guide holes is provided with wear-resistant nylon bushings.

4. The impact-recoverable friction pendulum pier according to any one of claims 1-3, characterized in that, The construction method of the impact-recoverable friction pendulum pier includes the following steps: S1: During the concrete pouring stage of the foundation cap and pier body, the foundation cap uses PVC pipe to reserve a 50mm diameter channel, and the energy dissipator is fixedly connected between the arc steel plate and the anchor plate. S2: After connecting the pier cap beam to the pier body, a smart tensioning system is used to implement staged tensioning: first apply 10%... Pre-tensioning to eliminate gaps in the steel strands; formal tensioning: applied in three stages to 105%. After each load level is held for 5 minutes, the tension is reduced to 100%. Locked; among which, To design the tension control stress.

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