Controllable restraint device for tower and beam of long-span cable-stayed bridge and design method thereof

Abstract

This invention discloses a controllable constraint device for the tower and beam of a long-span cable-stayed bridge and its design method. The device includes a fixed base at the tower end, a fixed base at the main beam end, a velocity locking component, and a tower-beam constraint shear key component. The fixed base at the tower end is anchored to the inner wall of the concrete structure of the tower via anchoring steel bars, and the fixed base at the main beam end is anchored to the outer wall of the main beam component via anchoring bars. The velocity locking component is fixedly installed on the outer wall of the fixed base at the tower end and can identify the relative velocity between the tower and the beam. Above a set velocity threshold, it automatically enters a locked state to transmit seismic loads. Under low-speed conditions such as operation and temperature deformation, it remains in a released state and does not participate in force transmission. The tower-beam constraint shear key component is located between the velocity locking component and the fixed base at the main beam end. It is used to provide constraint during minor earthquakes, limiting the relative displacement of the tower and beam. During major earthquakes, it releases the connection through controlled shearing to reduce the seismic internal forces of the structure, achieving "graded control" of the bridge structure's response.

Description

Technical Field

[0001] This invention belongs to the field of vibration reduction technology for bridge engineering structures, and more specifically, relates to a controllable constraint device for towers and beams of long-span cable-stayed bridges and its design method. Background Technology

[0002] Long-span cable-stayed bridges, with their superior spanning capacity, elegant structural design, and excellent mechanical properties, have become a core bridge type in large-scale transportation projects spanning rivers and seas, playing a crucial role in ensuring regional transportation connectivity and promoting the construction of major infrastructure projects. However, during their long service life, the connection between the main girder and the main tower (hereinafter referred to as "tower-girder") of a long-span cable-stayed bridge must continuously withstand various complex working conditions, including: dynamic traffic loads generated by vehicle movement, thermal expansion and contraction effects caused by changes in ambient temperature, wind loads under strong winds (including wind-induced vibrations such as flutter and vortex-induced vibration), and seismic loads faced in earthquake-prone areas (including earthquakes of different levels such as design intensity earthquakes and rare earthquakes).

[0003] In the current design of tower-beam connections for long-span cable-stayed bridges, the mainstream solutions are still limited to two extreme forms: "completely fixed" or "completely free," which makes it difficult to simultaneously meet the dual core requirements of "freedom of relative movement between tower and beam under normal working conditions" and "structural safety under seismic conditions." If a fully rigid tower-beam design is adopted, although it can limit the relative displacement of the tower and beam under small-magnitude earthquakes or conventional loads and reduce the risk of damage to ancillary facilities, the rigid connection will forcibly transmit huge seismic internal forces under large-magnitude earthquakes. This will cause the key stress-bearing parts of the tower and beam (such as the root of the bridge tower and the end of the main beam) to generate stresses far exceeding the design limits, which can easily lead to structural cracking, plastic damage or even overall failure, seriously threatening the seismic safety of the bridge. If a tower-beam fully release design is adopted (such as transmitting vertical force and lateral constraint only through supports, with no rigid connection in the longitudinal direction), although it can meet the longitudinal free deformation requirements of the main beam due to temperature and traffic load under normal working conditions and avoid the accumulation of temperature stress, the lack of effective constraint in the longitudinal direction of the tower-beam under small-scale earthquakes can easily lead to excessive relative displacement, resulting in problems such as expansion joint compression failure and support detachment. At the same time, it may cause vehicles on the bridge to bounce and become unstable, affecting driving safety. Under large-scale earthquakes, the unrestrained relative movement of the tower-beam may also cause the main beam to collide with the bridge tower, further aggravating structural damage.

[0004] In summary, traditional tower-beam connection methods have significant limitations when facing complex working conditions (especially the contradiction between seismic loads and normal deformation), and cannot achieve the graded response objective of "normal free deformation - small earthquake constrained displacement - large earthquake protected structure". Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a controllable constraint device for the tower and beam of a long-span cable-stayed bridge and its design method. Through the coordinated design of a velocity locker and a shear key, an adaptive connection state adjustment mechanism based on the relative motion speed of the tower and beam is constructed. This mechanism enables a graded control process of "release-constraint-release": Under low-speed conditions such as normal operation (traffic load, temperature changes), when the relative motion speed of the tower and beam is less than the locking threshold of the velocity locker, the device maintains a damped release state, satisfying the free deformation requirements of the main beam; under minor earthquake conditions (E1 earthquake), when the relative motion speed of the tower and beam exceeds this threshold, the velocity locker is triggered, and the device switches to a fixed constraint state, transmitting load through the shear key to control displacement; under major earthquake conditions (E2 earthquake), when the constraint force of the tower and beam reaches the design shear force of the shear key, the shear key undergoes controlled failure, and the device releases the tower-beam connection again. This graded control mechanism precisely adapts to the requirements of different working conditions on the tower-beam connection state, balancing the bridge's deformation coordination and structural safety.

[0006] To achieve the above objectives, according to one aspect of the present invention, a controllable constraint device for the tower and beam of a long-span cable-stayed bridge is provided, comprising a fixed base at the tower end, a fixed base at the main beam end, a velocity locking assembly, and a tower-beam constraint shear key assembly; wherein... The bridge tower end fixed base is anchored to the inner wall of the bridge tower concrete structure by anchoring steel bars, and the main beam end fixed base is anchored to the outer wall of the main beam component by anchoring steel bars. The speed locking component is fixedly installed on the outer wall of the fixed base at the end of the bridge tower. It can identify the relative speed between the tower and the beam. When the speed exceeds the set threshold, it automatically enters the locking state to transmit seismic loads. Under low-speed conditions such as operation and temperature deformation, it remains in the released state and does not participate in the transmission of force. The tower-beam constraint shear key assembly is located between the velocity locking assembly and the main beam end fixed base. It is used to provide constraint during minor earthquakes to limit the relative displacement of the tower and beam, and to release the connection through controlled shearing during major earthquakes to reduce the seismic internal forces of the structure, thereby achieving "graded control" of the bridge structure response.

[0007] Furthermore, the locking assembly includes mounting blocks, a main beam end fixing base, a speed lock connector, a speed lock, a bridge tower end fixing groove, and a bridge tower end sliding rail. Mounting blocks are fixedly installed on the inner sidewalls of both ends of the bridge tower end fixing base. The two mounting blocks are arranged opposite to each other, and speed lock connectors are fixedly installed on their opposite sidewalls. The end of the speed lock connector away from the mounting block is fixedly connected to the cylinder of the speed lock. The piston rod ends of the two speed locks are fixedly connected to both ends of the bridge tower end sliding rail. The bridge tower end fixing groove is fixedly installed at the middle position of the outer sidewall of the bridge tower end fixing base.

[0008] Furthermore, the inner cavity of the bridge tower end fixed slide groove has a rectangular structure, and its outer side wall has an opening that communicates with its own inner cavity. The cross-section of the bridge tower end sliding rail is T-shaped, and the end of the T-shaped bridge tower end sliding rail is adapted to be embedded in the inner cavity of the bridge tower end fixed slide groove to form a sliding fit structure, so that the bridge tower end sliding rail can reciprocate along the extension direction of the bridge tower end fixed slide groove.

[0009] Furthermore, the tower-beam constraint shear key assembly includes a main beam end fixed rail, a first shear key mounting seat, a second shear key mounting seat, and shear keys. The first shear key mounting seat is fixedly installed on the other side of the bridge tower end sliding rail, the main beam end fixed rail is fixedly installed on the other side of the main beam end fixed base, and the second shear key mounting seat is fixedly installed on the other side of the main beam end fixed rail. The structural dimensions of the first shear key mounting seat and the second shear key mounting seat are completely identical, and they are symmetrically arranged. Multiple shear keys are detachably connected between the first shear key mounting seat and the second shear key mounting seat by bolts.

[0010] Furthermore, multiple V-grooves are provided on the opposite sidewalls of the first and second shear key mounting seats. The V-grooves are evenly distributed along the length of the mounting seats, and the positions, number, and dimensions of the V-grooves on the two mounting seats correspond one-to-one. The opening of the multiple V-grooves forms multiple continuous trapezoidal protrusions on the opposite sides of the two mounting seats, and the ends of the trapezoidal protrusions are provided with through bolt holes.

[0011] Furthermore, the shear key has V-shaped shear grooves on both sides to form a preset shear section, and through bolt holes are provided at both ends of the shear key. The position, number and diameter of the bolt holes correspond one-to-one with the bolt holes at the ends of the trapezoidal protrusions of the two mounting seats.

[0012] Furthermore, the controllable constraint device is fixedly installed between the inner wall of the bridge tower and the outer wall of the main beam of the cable-stayed bridge, and each bridge tower is provided with a set of the controllable constraint device on each side of the main beam.

[0013] According to a second aspect of the present invention, a design method for a controllable constraint device for a long-span cable-stayed bridge tower and beam is provided, which is implemented using the aforementioned controllable constraint device for a long-span cable-stayed bridge tower and beam, and includes the following steps: S100: Use finite element software to establish a finite element model of the cable-stayed bridge; S200: Based on the finite element model of the cable-stayed bridge structure constructed in step S100, the longitudinal mechanical response of the tower and beam is calculated under two constraint states to obtain the core parameters required for the device design. S300: Based on the calculation results of step S200, determine the maximum stroke L of the speed lock 5 and the locking speed threshold vcr; S400: Based on the maximum constraint force FE1 at the tower-beam connection under minor earthquake E1 and the maximum constraint force FE2 at the tower-beam connection under major earthquake E2 calculated in step S220, calculate the shear strength F of shear key 11. cr， To ensure that shear key 11 achieves controllable failure under preset working conditions, its design parameters include shear tooth thickness t, shear tooth width a, and the number of shear teeth n, and the design shear force F. cr The calculation formula is: F cr =t•a•n•τ cr ; S500: Calculate the strength of the first shear key mounting base 9 and the second shear key mounting base 10. The ultimate bearing strength of the mounting base must be more than three times the design shear strength Fcr of the shear key, ensuring that the bearing capacity of the mounting base is much higher than the design shear strength Fcr of the shear key. The ultimate bearing capacity of the first shear key mounting base 9 and the second shear key mounting base 10 shall be designed according to the following requirements: F base ≥3×F cr ; Wherein: F base F represents the ultimate bearing capacity of the first shear key mounting base 9 and the second shear key mounting base 10. cr The design shear force for the shear key.

[0014] Furthermore, step S200 specifically includes the following steps: S210: Establish the floating model state of the tower and beam without longitudinal constraints, and apply wind load combination F respectively. w Traffic load combination F q The acceleration time histories a1(t) for minor earthquake E1 and a2(t) for major earthquake E2 are obtained. Using corresponding nonlinear analysis methods, the maximum relative displacement and maximum relative velocity response of the tower and beam along the longitudinal direction of the bridge under each working condition are calculated. This model is then used to evaluate the displacement and velocity threshold requirements that the device needs to adapt to under normal operating loads and seismic action. The specific steps are as follows: Longitudinal modal analysis was performed on the floating model to obtain the first-order vibration frequency f1 in the longitudinal direction of the bridge, which serves as a key basic parameter for subsequent velocity conversion. Apply wind load combination F to the model w The maximum displacement d of the main girder along the longitudinal direction of the bridge was calculated by nonlinear static analysis. w Based on the vibration frequency, the maximum longitudinal velocity of the main beam under the corresponding wind load is calculated: v w =2πf1d w ; Apply traffic load combination F to the model q The maximum displacement d of the main girder along the longitudinal direction of the bridge was calculated through dynamic response analysis. qSimilarly, the maximum longitudinal velocity of the main beam under traffic load can be calculated: v q =2πf1d q ; Input the acceleration time history a1(t) of a small-magnitude earthquake E1 into the model, perform nonlinear time history analysis, and calculate the maximum relative displacement dE1 and the maximum relative velocity vE1 of the tower and beam along the longitudinal direction of the bridge. Input the acceleration time history a2(t) of the large-magnitude earthquake E2 into the model, and use the same nonlinear time history analysis method to calculate the maximum relative displacement dE2 and the maximum relative velocity vE2 of the tower and beam along the longitudinal direction of the bridge. S220: Establish a fixed connection model with longitudinal constraints between the tower and the beam. Input the acceleration time history a1(t) for a small-magnitude earthquake E1 and the acceleration time history a2(t) for a large-magnitude earthquake E2. Using the same analysis logic, calculate the maximum relative displacement and maximum relative velocity response of the tower and beam along the longitudinal direction of the bridge under this constraint state. Use this model to evaluate the magnitude of the constraint force that the shear key needs to bear under different seismic conditions. The specific steps are as follows: Input the acceleration time history a1(t) of a small-magnitude earthquake E1 into the fixed connection model, perform nonlinear time history analysis of the seismic response, and calculate the maximum constraint force FE1 generated at the tower-beam connection. Input the acceleration time history a2(t) of a large-magnitude earthquake E2 into the fixed connection model, and use the same analysis method to calculate the maximum constraint force FE2 generated at the tower-beam connection.

[0015] Furthermore, the speed lock 5 must have sufficient displacement release capability in the unlocked state, and its maximum stroke L should cover the wind load combination F. w Traffic load combination F q The design formula is three times the maximum relative displacement of the tower and girder in the longitudinal direction under the action of minor earthquake E1 and major earthquake E2. This ensures the release requirements of the device in bidirectional displacement scenarios while reserving sufficient safety margin to avoid damage to the device due to excessive displacement. L = 3 × max(d) w ,d q ,dE1,dE2); Where: d w For wind load combination F w Maximum relative displacement of the lower tower beam, d q Traffic load combination F q The maximum relative displacement of the lower tower beam, dE1 is the maximum relative displacement of the lower tower beam in minor earthquake E1, dE2 is the maximum relative displacement of the lower tower beam in major earthquake E2; Lock speed v cr The trigger boundaries between normal operating conditions and seismic conditions need to be precisely defined, and should meet the requirements greater than those of normal operating conditions (wind load combination F).w Traffic load combination F q The maximum relative velocity of the lower tower beam in the longitudinal direction is less than the minimum relative velocity of the lower tower beam in the longitudinal direction under seismic conditions (minor earthquake E1, major earthquake E2), ensuring that the locking function is triggered only during seismic action and does not interfere with the free deformation of the structure during normal operation. The design constraints are as follows: max(v) w ,v q ) <vcr<min(vE1,vE2); Where: v w For wind load combination F w Maximum relative velocity of the lower tower beam, v q Traffic load combination F q The maximum relative velocity of the lower tower beam is given by vE1 (for minor earthquake E1) and vE2 (for major earthquake E2).

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The present invention discloses a controllable constraint device for tower-beam connection of a long-span cable-stayed bridge. Through the coordinated design of a velocity lock and a shear key, an adaptive connection state adjustment mechanism based on the relative motion speed of the tower and beam is constructed, enabling a graded control process of "release-constraint-release": Under low-speed conditions such as normal operation (traffic load, temperature changes), when the relative motion speed of the tower and beam is less than the locking threshold of the velocity lock, the device maintains a damped release state to meet the free deformation requirements of the main beam; under the condition of a minor earthquake (E1 earthquake), when the relative motion speed of the tower and beam exceeds the threshold, the velocity lock is triggered, and the device switches to a fixed constraint state, transmitting load through the shear key to control displacement; under the condition of a major earthquake (E2 earthquake), when the constraint force of the tower and beam reaches the design shear force of the shear key, the shear key undergoes controlled failure, and the device releases the tower-beam connection again. This graded control mechanism accurately adapts to the requirements of different working conditions for the tower-beam connection state, taking into account both the deformation coordination and structural safety of the bridge.

[0017] 2. The present invention provides a controllable constraint device for the tower and beam of a long-span cable-stayed bridge. Through the coordinated design of a velocity-sensitive locker and a controllable shear element, a differentiated response strategy is formed. Under normal conditions, the velocity locker does not trigger locking, and the main beam can freely expand and contract to release temperature deformation, avoiding structural damage caused by temperature stress accumulation and ensuring the comfort of bridge use. Under seismic action, the device locks under minor earthquake conditions to constrain the relative displacement of the tower and beam, and under major earthquake conditions, the shear key is promptly sheared to release the connection. This effectively balances the core requirements of normal bridge operation and earthquake safety, filling the technical gap of traditional solutions.

[0018] 3. The controllable constraint device for towers and beams of a long-span cable-stayed bridge, as described in this invention, significantly improves the seismic performance of cable-stayed bridges through the seismic design logic of "constraint during minor earthquakes and release during major earthquakes." Under minor earthquake conditions, after the device is locked, it provides appropriate stiffness through shear keys, which can effectively limit the longitudinal relative displacement between the main beam and the bridge tower, and prevent damage to ancillary facilities such as expansion joints and supports due to excessive displacement. Under major earthquake conditions, the shear keys are precisely sheared according to the preset load, the tower-beam connection is released, and the bridge as a whole enters the flexible response stage. The main beam can dissipate seismic energy through controllable swinging, which greatly reduces the peak internal forces of the bridge tower and the main beam, avoids catastrophic structural damage caused by concentrated seismic energy, and significantly reduces the risk of structural damage and repair costs.

[0019] 4. The controllable constraint device for towers and beams of long-span cable-stayed bridges of the present invention has a compact overall structure and flexible layout. It can be directly anchored to the inner wall of the bridge tower and the outer wall of the main beam through anchor bars, without the need for large-scale modification of the main structure of the cable-stayed bridge (bridge tower, main beam, and stay cables). It is suitable for the installation requirements of cable-stayed bridges with different spans and structural forms. After a major earthquake, the device function can be restored simply by disassembling the bolts and replacing the damaged shear keys. There is no need to replace other core components. The maintenance process is simple and time-saving, which significantly reduces the later operation and maintenance costs. It is economical and practical.

[0020] 5. The present invention provides a controllable constraint device for the tower and beam of a long-span cable-stayed bridge. By constructing a finite element model of the cable-stayed bridge and calculating the mechanical response of the tower and beam under different constraint states, the key parameters such as the stroke L of the speed lock, the locking speed, and the shear force of the shear key are quantitatively determined. This achieves a precise match between the device performance and the bridge structure response, providing a clear and replicable technical basis for the selection of devices and parameter optimization for cable-stayed bridges of different scales and in different regions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the installation structure on both sides of the bridge tower of a controllable constraint device for a long-span cable-stayed bridge tower beam according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the installation structure of a controllable constraint device for a long-span cable-stayed bridge tower and beam according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a controllable constraint device for a long-span cable-stayed bridge tower and beam according to an embodiment of the present invention; Figure 4 This is an exploded structural diagram of a controllable constraint device for a long-span cable-stayed bridge tower and beam according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the shear key structure of a controllable constraint device for a long-span cable-stayed bridge tower beam according to an embodiment of the present invention; Figure 6 This is a detailed structural diagram of the first shear key mounting base and the second shear key mounting base of a controllable constraint device for a long-span cable-stayed bridge tower beam according to an embodiment of the present invention. Figure 7 This is a flowchart illustrating a design method for a controllable constraint device for a long-span cable-stayed bridge tower and beam, according to an embodiment of the present invention.

[0022] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-bridge tower end fixed base, 2-mounting block, 3-main beam end fixed base, 4-speed locker connector, 5-speed locker, 6-bridge tower end fixed slide groove, 7-bridge tower end sliding rail, 8-main beam end fixed rail, 9-first shear key mounting seat, 10-second shear key mounting seat, 11-shear key. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] In this patent, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0027] Example 1 like Figure 1-6 As shown in the figure, this embodiment of the invention provides a controllable constraint device for the tower and beam of a long-span cable-stayed bridge, including a bridge tower end fixed base 1, a main beam end fixed base 3, a velocity locking component, and a tower-beam constraint shear key component. The bridge tower end fixed base 1 is anchored to the inner wall of the bridge tower concrete structure via anchoring steel bars. The main beam end fixed base 3 is anchored to the outer wall of the main beam component via anchoring steel bars. The velocity locking component is fixedly installed on the outer wall of the bridge tower end fixed base and can identify the relative velocity between the tower and beam. Above a set velocity threshold, it automatically enters a locked state to transmit seismic loads. Under low-speed conditions such as operation and temperature deformation, it remains in a released state and does not participate in force transmission. The tower-beam constraint shear key component is located between the velocity locking component and the main beam end fixed base 3. It is used to provide constraint during minor earthquakes, limiting the relative displacement of the tower and beam. During major earthquakes, it releases the connection through controlled shearing to reduce the structural seismic internal forces, achieving "graded control" of the bridge structure response. This invention, through the coordinated operation of the fixed base at the bridge tower end, the fixed base at the main beam end, the speed locking component, and the tower-beam constraint shear key component, can automatically switch the constraint state according to the speed and load level of the relative motion between the tower and the beam. It effectively balances the freedom of relative motion under normal bridge conditions and the safety under seismic conditions, and solves the problems that traditional tower-beam fixed connection is prone to structural damage in large earthquakes and that fully released connection is prone to excessive displacement of the main beam and damage to auxiliary facilities under small earthquakes. Further, the locking assembly includes mounting blocks 2, speed lock connectors 4, speed locks 5, bridge tower end fixing grooves 6, and bridge tower end sliding rails 7. Mounting blocks 2 are fixedly installed on the inner walls of both ends of the bridge tower end fixing base 1. The two mounting blocks 2 are arranged opposite each other, and speed lock connectors 4 are fixedly installed on their opposite side walls. The end of the speed lock connector 4 away from the mounting block is fixedly connected to the cylinder of the speed lock 5 to achieve a stable assembly of the speed lock in the locking assembly. The piston rod ends of the two speed locks 5 are jointly fixedly connected to both ends of the bridge tower end sliding rail 7, forming the power transmission link of the locking assembly. The bridge tower end fixing groove 6 is fixedly installed at the middle position of the outer wall of the bridge tower end fixing base. The inner... The cavity has a rectangular structure, and its outer wall has an opening that communicates with its inner cavity, providing space for the assembly and movement of the bridge tower end sliding rail. The cross-section of the bridge tower end sliding rail 7 is T-shaped, and the end of the T-shaped bridge tower end sliding rail is adapted to be embedded in the inner cavity of the bridge tower end fixed sliding groove, forming a sliding fit structure, so that the bridge tower end sliding rail 7 can slide back and forth along the extension direction of the bridge tower end fixed sliding groove 6 to adapt to the relative displacement requirements between the tower and the beam under different working conditions. The speed lock device 5 accurately identifies the relative speed between the tower and the beam, and keeps it in the released state during normal operation to adapt to low-speed displacement caused by temperature deformation, vehicle load, etc., and avoid additional structural stress. Under small earthquake conditions, the speed lock device 5 is triggered and locked, and works with the tower and beam constraint shear key assembly to assume the constraint role, limit the relative displacement between the tower and the beam, and protect expansion joints and other auxiliary facilities.

[0028] Furthermore, the inner cavity end face of the bridge tower end fixed slide groove 6 can be selected from elliptical, rhomboid, or figure-eight shaped structures; correspondingly, the end face shape of the bridge tower end sliding rail 7 is elliptical, rhomboid, or figure-eight shaped to match the inner cavity end face of the bridge tower end fixed slide groove 6, so as to ensure that the end of the bridge tower end sliding rail 7 can be stably embedded in the inner cavity of the bridge tower end fixed slide groove 6 and achieve smooth sliding along the extension direction of the bridge tower end fixed slide groove 6, while ensuring the stress stability and motion reliability of the two mating structures.

[0029] Further, the tower-beam constraint shear key assembly includes a main beam end fixed rail 8, a first shear key mounting seat 9, a second shear key mounting seat 10, and a shear key 11; wherein, the first shear key mounting seat 9 is fixedly installed on the other side of the bridge tower end sliding rail 7, forming a stable connection with the bridge tower end sliding rail, providing one-sided installation support for the shear key; the main beam end fixed rail 8 is fixedly installed on the other side of the main beam end fixed base 3, and the second shear key mounting seat 10 is fixedly installed on the other side of the main beam end fixed rail 8, together with the main beam end fixed rail 8, forming the other side installation support structure of the shear key; the first The shear key mounting base 9 and the second shear key mounting base 10 have completely identical structural dimensions and are arranged symmetrically. Multiple shear keys 11 are detachably connected between the first and second shear key mounting bases via bolts. The shear keys are made of mild steel and are assembled with the two mounting bases via bolts to achieve force transmission connection between the shearing component and the bridge tower end sliding rail and the main beam end fixed rail. They can bear constraint loads to limit the relative displacement of the tower and beam under minor earthquake conditions, and perform controlled shearing according to the preset design under major earthquake conditions, thereby releasing the tower and beam connection and adapting to the structural stress requirements under different seismic conditions.

[0030] Furthermore, the first shear key mounting base 9 and the second shear key mounting base 10 of the present invention are provided with a plurality of spaced V-shaped grooves on their opposite sidewalls. The V-shaped grooves are evenly distributed along the length of the mounting base, and the positions, number and size of the V-shaped grooves on the two mounting bases correspond one-to-one. The opening of the plurality of V-shaped grooves forms a plurality of continuous trapezoidal protrusions on the opposite sides of the two mounting bases, and the ends of the trapezoidal protrusions are provided with through bolt holes.

[0031] Furthermore, the shear key 11 has V-shaped shear grooves on both sides to form a preset shear section, ensuring that the shear key 11 undergoes controlled shearing along this section under strong earthquake conditions. At the same time, the shear key 11 has through bolt holes at both ends. The position, number, and diameter of the bolt holes correspond one-to-one with the bolt holes at the ends of the trapezoidal protrusions of the two mounting seats, so that the shear key 11 and the mounting seats can be detachably connected by bolts, which not only ensures the reliability of the connection but also provides convenience for later maintenance and replacement.

[0032] Furthermore, the controllable constraint device is fixedly installed between the inner wall of the bridge tower and the outer wall of the main beam of the cable-stayed bridge, and each bridge tower has a set of the controllable constraint device arranged on both sides of the main beam. The device is stably assembled between the tower and the beam by anchoring the fixed base 1 at the bridge tower end to the anchor bar of the inner wall of the bridge tower and the fixed base 3 at the main beam end to the anchor bar of the outer wall of the main beam, so as to ensure the reliability of force transmission and structural stability under various working conditions, while adapting to the relative movement space requirements between the tower and the beam.

[0033] Specifically, during normal operation of a cable-stayed bridge, the main girder experiences longitudinal displacement due to traffic loads, but the velocity of this displacement is relatively low. Simultaneously, changes in ambient temperature cause longitudinal deformation of the main girder due to thermal expansion and contraction. Under these conditions, the longitudinal displacement of the main girder caused by traffic loads is typically controlled within the allowable displacement range of the expansion joints at the ends of the main girder, meeting usage requirements without additional constraints. However, if the deformation of the main girder caused by temperature changes is forcibly constrained, it can easily lead to temperature stresses within the main girder exceeding the material's tolerance limits, thereby causing structural cracking or damage. Therefore, during normal operation, the controllable constraint device of this tower-girder must maintain a damped constraint state.

[0034] At this time, the relative speed between the tower and the beam is less than the locking speed threshold of the speed locker. The speed locker does not trigger the locking function, but only provides moderate damping force through its own damping characteristics, which effectively reduces the longitudinal vibration displacement of the bridge under dynamic loads such as traffic flow and wind load, and reduces structural vibration fatigue damage. The device as a whole maintains the integrity of the structure, with no component failure, ensuring the stability and safety of the bridge's normal operation.

[0035] When a cable-stayed bridge encounters a minor earthquake (i.e., a design intensity of E1), the differences in mass and stiffness between the bridge towers and the main girder suspended by the cables result in different natural vibration characteristics, leading to significant relative longitudinal movement. Although the relative displacement between the towers and the girder is small due to the low intensity of the E1 earthquake, it may still cause damage to bridge expansion joints and other ancillary facilities due to excessive displacement if not properly restrained. Furthermore, the relative movement between the towers and the girder caused by the earthquake can easily cause vehicles traveling on the bridge to experience bumps and instability, affecting driving safety.

[0036] Under this condition, the relative speed between the tower and the beam exceeds the locking speed threshold of the speed lock, and the speed lock quickly triggers the locking function. The device switches from the normal damping constraint state to the fixed constraint state. At this time, the shear key of the tower-beam constraint bears the load required to coordinate the relative displacement of the tower and the beam, and the stress actually borne by the shear key is less than the stress safety threshold corresponding to its design shear force. The shear key maintains the structural integrity and does not fail to shear. The fixed constraint of the device effectively controls the relative displacement of the tower and the beam, thereby protecting the bridge's ancillary facilities and traffic safety.

[0037] When a cable-stayed bridge encounters a major earthquake (i.e., a rare earthquake E2), according to the seismic design principle, the main girder suspended by the cable stays is in a controlled swing state. Through the kinetic energy dissipation and vibration attenuation during the swing process, the seismic internal forces borne by the main girder and the bridge tower can be effectively reduced. If the tower and the girder remain in a fixed state at this time, the seismic energy will be concentrated and transferred to the key stress-bearing parts of the bridge tower and the main girder, which will aggravate the seismic response of the structure and even cause serious damage such as the tilting of the bridge tower and the fracture of the main girder, which will have an extremely adverse effect on the overall seismic performance of the cable-stayed bridge.

[0038] Under E2 seismic loading, the relative velocity between the tower and the girder is much greater than the locking velocity threshold of the velocity locker. The velocity locker has already triggered its locking function and maintained a fixed constraint state. At this point, the constraint force between the tower and the girder rapidly reaches the design shear force of the shear key. The shear key undergoes controlled shearing along the preset shear section, thereby releasing the fixed constraint between the tower and the girder. After the constraint is released, the main girder can swing controllably under the suspension of the stay cables. By swinging, a large amount of seismic energy is dissipated, significantly reducing the peak seismic internal forces of the main girder and the bridge tower. Ultimately, the core seismic resistance objective of protecting the main structure of the bridge and avoiding catastrophic damage is achieved.

[0039] Example 2 Combination Figure 1-6 ,like Figure 7 As shown, this invention provides a design method for a controllable constraint device for the tower and beam of a long-span cable-stayed bridge. The method utilizes the aforementioned controllable constraint device for the tower and beam of a long-span cable-stayed bridge, and the specific steps are as follows: S100: Use finite element software to establish a finite element model of the cable-stayed bridge; Using finite element analysis software, a finite element model of the cable-stayed bridge structure with parameters consistent with the actual cable-stayed bridge structure is constructed. The model must accurately reproduce the geometric dimensions, material properties, connection methods, and boundary conditions of core components such as bridge towers, main beams, and stay cables to ensure that the model can realistically reflect the mechanical response characteristics of the bridge under different loads and seismic actions. All input parameters required for the design of this device are clearly defined, specifically including the wind load combination F. w Traffic load combination F q The input acceleration time history a1(t) for a minor earthquake (design intensity earthquake) E1 and the input acceleration time history a2(t) for a major earthquake (rare earthquake); wherein, the wind load combination F w The parameters must include basic wind pressure, wind-induced flutter and vortex-induced vibration of the main girder, and other wind load-related parameters for the area where the structure is located, and must be corrected for wind pressure height variation coefficients based on the terrain conditions of the bridge; the traffic load combination F q The load combination coefficients should be determined based on the actual traffic flow and vehicle type distribution, taking into account the uniformly distributed live load, concentrated live load, and dynamic impact effects during vehicle movement. The input acceleration time histories a1(t) and a2(t) of the small-magnitude earthquake E1 and the large-magnitude earthquake E2 should be selected or synthesized in conjunction with the seismic motion parameter zoning results of the area where the bridge is located to ensure the rationality and relevance of the seismic input. All the above load data and seismic input data must strictly comply with the specific requirements of relevant national standards and industry specifications such as the "Code for Seismic Design of Highway Bridges" (JTG / T2231-2020) or the "Code for Design of Urban Bridges" (CJJ11-2019) to provide accurate and reliable basic data support for subsequent structural dynamic response calculations and device parameter design.

[0040] S200: Based on the finite element model of the cable-stayed bridge structure constructed in step S100, the longitudinal mechanical response of the tower and beam is calculated under two constraint states to obtain the core parameters required for the device design. S210: Establish the floating model state of the tower and beam without longitudinal constraints, and apply wind load combination F respectively. w Traffic load combination F q The acceleration time histories a1(t) for minor earthquake E1 and a2(t) for major earthquake E2 are obtained. Using corresponding nonlinear analysis methods, the maximum relative displacement and maximum relative velocity response of the tower and beam along the longitudinal direction of the bridge under each working condition are calculated. This model is then used to evaluate the displacement and velocity threshold requirements that the device needs to adapt to under normal operating loads and seismic action. The specific steps are as follows: Longitudinal modal analysis was performed on the floating model to obtain the first-order vibration frequency f1 in the longitudinal direction of the bridge, which serves as a key basic parameter for subsequent velocity conversion. Apply wind load combination F to the model w The maximum displacement d of the main girder along the longitudinal direction of the bridge was calculated by nonlinear static analysis. w Based on the vibration frequency, the maximum longitudinal velocity of the main beam under the corresponding wind load is calculated: v w =2πf1d w ; Apply traffic load combination F to the model q The maximum displacement d of the main girder along the longitudinal direction of the bridge was calculated through dynamic response analysis. q Similarly, the maximum longitudinal velocity of the main beam under traffic load can be calculated: v q =2πf1d q ; Input the acceleration time history a1(t) of a small-magnitude earthquake E1 into the model, perform nonlinear time history analysis, and calculate the maximum relative displacement dE1 and the maximum relative velocity vE1 of the tower and beam along the longitudinal direction of the bridge. Input the acceleration time history a2(t) of the large-magnitude earthquake E2 into the model, and use the same nonlinear time history analysis method to calculate the maximum relative displacement dE2 and the maximum relative velocity vE2 of the tower and beam along the longitudinal direction of the bridge. S220: Establish a fixed connection model with longitudinal constraints between the tower and the beam. Input the acceleration time history a1(t) for a small-magnitude earthquake E1 and the acceleration time history a2(t) for a large-magnitude earthquake E2. Using the same analysis logic, calculate the maximum relative displacement and maximum relative velocity response of the tower and beam along the longitudinal direction of the bridge under this constraint state. Use this model to evaluate the magnitude of the constraint force that the shear key needs to bear under different seismic conditions. The specific steps are as follows: Input the acceleration time history a1(t) of a small-magnitude earthquake E1 into the fixed connection model, perform nonlinear time history analysis of the seismic response, and calculate the maximum constraint force FE1 generated at the tower-beam connection. Input the acceleration time history a2(t) of a large-magnitude earthquake E2 into the fixed connection model, and use the same analysis method to calculate the maximum constraint force FE2 generated at the tower-beam connection. Based on the calculation results of the above floating model and fixed model, the displacement / velocity range and shear key bearing requirements of the device are clarified, providing direct quantitative basis for the subsequent design of the locking threshold, stroke parameters, shear force, and structural dimensions of the velocity locker.

[0041] S300: Based on the calculation results of step S200, determine the maximum stroke L of the speed lock and the locking speed threshold vcr; Speed ​​locker maximum stroke L design: The speed locker must have sufficient displacement release capacity in the unlocked state, and its maximum stroke L should cover the wind load combination F. w Traffic load combination F q The design formula is three times the maximum relative displacement of the tower and girder in the longitudinal direction under the action of minor earthquake E1 and major earthquake E2. This ensures the release requirements of the device in bidirectional displacement scenarios while reserving sufficient safety margin to avoid damage to the device due to excessive displacement. L = 3 × max(d) w ,d q ,dE1,dE2); Where: d w For wind load combination F w Maximum relative displacement of the lower tower beam, d q Traffic load combination F q The maximum relative displacement of the lower tower beam, dE1 is the maximum relative displacement of the lower tower beam in minor earthquake E1, dE2 is the maximum relative displacement of the lower tower beam in major earthquake E2; Lock speed v cr The trigger boundaries between normal operating conditions and seismic conditions need to be precisely defined, and should meet the requirements greater than those of normal operating conditions (wind load combination F). w Traffic load combination F q The maximum relative velocity of the lower tower beam in the longitudinal direction is less than the minimum relative velocity of the lower tower beam in the longitudinal direction under seismic conditions (minor earthquake E1, major earthquake E2), ensuring that the locking function is triggered only during seismic action and does not interfere with the free deformation of the structure during normal operation. The design constraints are as follows: Max(v) w ,v q ) <vcr<min(vE1,vE2); Where: v w For wind load combination F w Maximum relative velocity of the lower tower beam, vq Traffic load combination F q The maximum relative velocity of the lower tower beam, vE1 is the maximum relative velocity of the lower tower beam during minor earthquake E1, vE2 is the maximum relative velocity of the lower tower beam during major earthquake E2; S400: Based on the maximum constraint force FE1 at the tower-beam connection under minor earthquake E1 and the maximum constraint force FE2 at the tower-beam connection under major earthquake E2 calculated in step S220, calculate the shear strength F of the shear key. cr， Ensure that the shear key achieves controllable failure under preset working conditions; Shear key design with shear force F cr It needs to meet the functional requirements of "bearing under minor earthquakes and shearing under major earthquakes". It should be greater than the tower-beam constraint force FE1 under minor earthquake E1 and less than the tower-beam constraint force FE2 under major earthquake E2, so as to achieve graded controllable failure under seismic conditions. like Figure 5-6 As shown, the shear key 11 is made of mild steel. V-shaped shear grooves are formed on both sides of the shear key 11 to create a pre-defined shear cross-section. Its design parameters include the shear tooth thickness t, the shear tooth width a, and the number of shear teeth n. The design shear force F is... cr The calculation formula is: F cr =t•a•n•τ cr； In actual design, under the premise of satisfying this equation, the thickness t, width a, and number n of the shear teeth can be optimized by taking into account the feasibility of processing technology, installation space requirements, and manufacturing convenience, so as to ensure that the shear key structure meets both mechanical performance requirements and engineering practicality.

[0042] Furthermore, the possible values ​​are the average of FE1 and FE2, i.e., F cr =0.5×(FE1+FE2), this value can balance the reliability of small earthquake constraint and the timeliness of large earthquake shear.

[0043] S500: Calculate the strength of the first shear key mounting base and the second shear key mounting base to ensure that the load-bearing capacity of the mounting base is much higher than the design shear force Fcr of the shear key, so as to realize the preset failure mode of "only the shear key is sheared first and the mounting base remains intact" under seismic conditions, and avoid the mounting base being damaged prematurely due to insufficient strength, thus affecting the function of the device. The ultimate bearing capacity of the first shear key mounting base and the second shear key mounting base shall be designed according to the following requirements: F base ≥3×F cr ; Wherein: F base F represents the ultimate bearing capacity of the first shear key mounting base and the second shear key mounting base. cr Design shear force for shear key; Structural strength design was carried out for the first and second shear key mounting seats. The core design principle is that the ultimate bearing strength of the mounting seat must be more than three times the design shear strength Fcr of the shear key. When the tower-beam constraint force reaches Fcr under a major earthquake, the shear key will preferentially undergo controlled shear failure, while the mounting seat will remain structurally intact due to sufficient strength redundancy. This avoids damage to other critical parts of the device (such as the bridge tower end sliding rail and the main beam end fixed rail) due to the failure of the mounting seat. At the same time, it provides a stable structural foundation for the later replacement of only the shear key, which greatly reduces operation and maintenance costs and construction difficulty.

[0044] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A controllable constraint device for the tower and beam of a long-span cable-stayed bridge, characterized in that, This includes a bridge tower end fixed base (1), a main beam end fixed base (3), a velocity locking assembly, and a tower-beam constraint shear key assembly; among which, The bridge tower end fixed base (1) is anchored to the inner wall of the bridge tower concrete structure by anchoring steel bars, and the main beam end fixed base (3) is anchored to the outer wall of the main beam component by anchoring steel bars. The speed locking component is fixedly installed on the outer wall of the fixed base at the end of the bridge tower. It can identify the relative speed between the tower and the beam. When the speed exceeds the set threshold, it automatically enters the locking state to transmit seismic loads. Under low-speed conditions such as operation and temperature deformation, it remains in the released state and does not participate in the transmission of force. The tower-beam constraint shear key assembly is located between the velocity locking assembly and the main beam end fixed base (3). It is used to bear the constraint effect and limit the relative displacement of the tower-beam during minor earthquakes. During major earthquakes, it releases the connection through controlled shearing to reduce the seismic internal force of the structure and realize the "graded control" of the bridge structure response.

2. The controllable constraint device for the tower and beam of a long-span cable-stayed bridge according to claim 1, characterized in that, The locking assembly includes a mounting block (2), a speed lock connector (4), a speed lock (5), a bridge tower end fixing groove (6), and a bridge tower end sliding rail (7). The inner walls of both ends of the bridge tower end fixing base (1) are fixedly provided with mounting blocks (2). The two mounting blocks (2) are arranged opposite to each other, and the speed lock connector (4) is fixedly installed on the opposite side walls of both. The end of the speed lock connector (4) away from the mounting block is fixedly connected to the cylinder of the speed lock (5). The piston rod ends of the two speed locks (5) are fixedly connected to both ends of the bridge tower end sliding rail (7). The bridge tower end fixing groove (6) is fixedly installed in the middle of the outer wall of the bridge tower end fixing base.

3. The controllable constraint device for the tower and beam of a long-span cable-stayed bridge according to claim 2, characterized in that, The inner cavity of the bridge tower end fixed slide groove (6) is rectangular, and its outer side wall has an opening that communicates with its own inner cavity. The cross-section of the bridge tower end sliding rail (7) is T-shaped. The end of the T-shaped bridge tower end sliding rail is adapted to be embedded in the inner cavity of the bridge tower end fixed slide groove to form a sliding fit structure, so that the bridge tower end sliding rail (7) can slide back and forth along the extension direction of the bridge tower end fixed slide groove (6).

4. The controllable constraint device for the tower and beam of a long-span cable-stayed bridge according to claim 1, characterized in that, The tower-beam constraint shear key assembly includes a main beam end fixed rail (8), a first shear key mounting seat (9), a second shear key mounting seat (10), and shear keys (11). The first shear key mounting seat (9) is fixedly installed on the other side of the bridge tower end sliding rail (7). The main beam end fixed rail (8) is fixedly installed on the other side of the main beam end fixed base (3). The second shear key mounting seat (10) is fixedly installed on the other side of the main beam end fixed rail (8). The structural dimensions of the first shear key mounting seat (9) and the second shear key mounting seat (10) are completely consistent. They are arranged symmetrically. Multiple shear keys (11) are detachably connected between the first shear key mounting seat (9) and the second shear key mounting seat (10) by bolts.

5. The controllable constraint device for the tower and beam of a long-span cable-stayed bridge according to claim 4, characterized in that, The first shear key mounting base (9) and the second shear key mounting base (10) each have multiple spaced V-shaped grooves on their opposite sidewalls. The V-shaped grooves are evenly distributed along the length of the mounting base, and the position, number and size of the V-shaped grooves on the two mounting bases correspond one-to-one. The opening of the multiple V-shaped grooves makes the opposite sides of the two mounting bases form multiple continuous trapezoidal protrusions. The ends of the trapezoidal protrusions are all provided with through bolt holes.

6. The controllable constraint device for the tower and beam of a long-span cable-stayed bridge according to claim 5, characterized in that, The shear key (11) has V-shaped shear grooves on both sides to form a preset shear section. The shear key (11) has through bolt holes at both ends. The position, number and diameter of the bolt holes correspond one-to-one with the bolt holes at the ends of the trapezoidal protrusions of the two mounting seats.

7. A controllable constraint device for the tower and beam of a long-span cable-stayed bridge according to any one of claims 1-6, characterized in that, The controllable constraint device is fixedly installed between the inner wall of the bridge tower and the outer wall of the main beam of the cable-stayed bridge, and each bridge tower has a set of the controllable constraint device arranged on both sides of the main beam.

8. A design method for a controllable constraint device for the tower and beam of a long-span cable-stayed bridge, characterized in that, The controllable constraint device for the tower and beam of a long-span cable-stayed bridge as described in any one of claims 1-7 is characterized by comprising the following steps: S100: Use finite element software to establish a finite element model of the cable-stayed bridge; S200: Based on the finite element model of the cable-stayed bridge structure constructed in step S100, the longitudinal mechanical response of the tower and beam is calculated under two constraint states to obtain the core parameters required for the device design. S300: Based on the calculation results of step S200, determine the maximum stroke L of the speed lock (5) and the locking speed threshold vcr; S400: Calculate the maximum constraint force FE1 at the tower-beam connection under minor earthquake E1 and the maximum constraint force FE2 at the tower-beam connection under major earthquake E2. Calculate the shear strength F of the shear key (11). cr， To ensure that the shear key (11) achieves controllable failure under preset working conditions, its design parameters include shear tooth thickness t, shear tooth width a, and the number of shear teeth n, and the design shear force F. cr The calculation formula is: F cr =t•a•n•τ cr ; S500: Calculate the strength of the first shear key mounting base (9) and the second shear key mounting base (10). The ultimate bearing strength of the mounting base must be more than 3 times the design shear strength Fcr of the shear key to ensure that the bearing capacity of the mounting base is much higher than the design shear strength Fcr of the shear key. The ultimate bearing capacity of the first shear key mounting base (9) and the second shear key mounting base (10) shall be designed according to the following requirements: F base ≥3×F cr ; Wherein: F base F represents the ultimate bearing capacity of the first shear key mounting base (9) and the second shear key mounting base (10). cr The design shear force for the shear key (11).

9. The design method of a controllable constraint device for a long-span cable-stayed bridge tower and beam according to claim 8, characterized in that, S200 specifically includes the following steps: S210: Establish the floating model state of the tower and beam without longitudinal constraints, and apply wind load combination F respectively. w Traffic load combination F q The acceleration time histories a1(t) for minor earthquake E1 and a2(t) for major earthquake E2 are obtained. Using corresponding nonlinear analysis methods, the maximum relative displacement and maximum relative velocity response of the tower and beam along the longitudinal direction of the bridge under each working condition are calculated. This model is then used to evaluate the displacement and velocity threshold requirements that the device needs to adapt to under normal operating loads and seismic action. The specific steps are as follows: Longitudinal modal analysis was performed on the floating model to obtain the first-order vibration frequency f1 in the longitudinal direction of the bridge, which serves as a key basic parameter for subsequent velocity conversion. Apply wind load combination F to the model w The maximum displacement d of the main girder along the longitudinal direction of the bridge was calculated by nonlinear static analysis. w Based on the vibration frequency, the maximum longitudinal velocity of the main beam under the corresponding wind load is calculated: v w =2πf1d w ; Apply traffic load combination F to the model q The maximum displacement d of the main girder along the longitudinal direction of the bridge was calculated through dynamic response analysis. q Similarly, the maximum longitudinal velocity of the main beam under traffic load can be calculated: v q =2πf1d q ; Input the acceleration time history a1(t) of a small-magnitude earthquake E1 into the model, perform nonlinear time history analysis, and calculate the maximum relative displacement dE1 and the maximum relative velocity vE1 of the tower and beam along the longitudinal direction of the bridge. Input the acceleration time history a2(t) of the large-magnitude earthquake E2 into the model, and use the same nonlinear time history analysis method to calculate the maximum relative displacement dE2 and the maximum relative velocity vE2 of the tower and beam along the longitudinal direction of the bridge. S220: Establish a fixed connection model with longitudinal constraints between the tower and the beam. Input the acceleration time history a1(t) for a small-magnitude earthquake E1 and the acceleration time history a2(t) for a large-magnitude earthquake E2. Using the same analysis logic, calculate the maximum relative displacement and maximum relative velocity response of the tower and beam along the longitudinal direction of the bridge under this constraint state. Use this model to evaluate the magnitude of the constraint force that the shear key needs to bear under different seismic conditions. The specific steps are as follows: Input the acceleration time history a1(t) of a small-magnitude earthquake E1 into the fixed connection model, perform nonlinear time history analysis of the seismic response, and calculate the maximum constraint force FE1 generated at the tower-beam connection. Input the acceleration time history a2(t) of a large-magnitude earthquake E2 into the fixed connection model, and use the same analysis method to calculate the maximum constraint force FE2 generated at the tower-beam connection.

10. The design method of a controllable constraint device for a long-span cable-stayed bridge tower and beam according to claim 8, characterized in that, The speed lock (5) must have sufficient displacement release capability in the unlocked state, and its maximum stroke L should cover the wind load combination F. w Traffic load combination F q The design formula is three times the maximum relative displacement of the tower and girder in the longitudinal direction under the action of minor earthquake E1 and major earthquake E2. This ensures the release requirements of the device in bidirectional displacement scenarios while reserving sufficient safety margin to avoid damage to the device due to excessive displacement. L=3×max(d w ,d q ,dE1,dE2); Where: d w For wind load combination F w Maximum relative displacement of the lower tower beam, d q Traffic load combination F q The maximum relative displacement of the lower tower beam, dE1 is the maximum relative displacement of the lower tower beam in minor earthquake E1, dE2 is the maximum relative displacement of the lower tower beam in major earthquake E2; Lock speed v cr The trigger boundaries between normal operating conditions and seismic conditions need to be precisely defined, and should meet the requirements greater than those of normal operating conditions (wind load combination F). w Traffic load combination F q The maximum relative velocity of the lower tower beam in the longitudinal direction is less than the minimum relative velocity of the lower tower beam in the longitudinal direction under seismic conditions (minor earthquake E1, major earthquake E2), ensuring that the locking function is triggered only during seismic action and does not interfere with the free deformation of the structure during normal operation. The design constraints are as follows: max(v w ,v q )<vcr<min(vE1,vE2); Where: v w For wind load combination F w Maximum relative velocity of the lower tower beam, v q Traffic load combination F q The maximum relative velocity of the lower tower beam is given by vE1 (for minor earthquake E1) and vE2 (for major earthquake E2).

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