During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction ...During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.展开更多
The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce s...The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce some high-tech dynamic control devices to reduce dynamic response for double-deck cable-stayed bridges under earthquakes.A(90+128)m-span double-deck cable-stayed bridge with a steel truss beam is taken as the prototype bridge.A 3D finite element model is built to conduct the nonlinear time-history analysis of different site categories in fortification intensityⅨ(0.40 g)degree area.Two new types of dynamic control devices-cable sliding friction aseismic bearings(CSFABs)and elasticity fluid viscous dampers composite devices(EVFDs)are introduced to reduce the dynamic responses of double-deck cable-stayed bridges with steel truss beam.The parametric optimization design for the damping coefficient C and the elastic stiffness of spring K of EVFDs is conducted.The following conclusions are drawn:(1)The hybrid support system by EVFDs and CSFABs play a good function under both seismic and regular work,especially in eliminating the expansion joints damage;(2)The hybrid support system can reduce the beam-end displacement by 75%and the tower-bottom bending moment by 60%under the longitudinal seismic excitation.In addition,it can reduce the pier-bottom bending moment by at least 45%under transverse seismic and control the relative displacement between the pier and beam within 0.3 m.(3)Assuming the velocity indexα=0.3,the parametric optimization suggests the damping coefficient C as 2000 kN·s·m-1in siteⅠ0,4000kN·s·m-1in siteⅡ,6000 kN·s·m-1in siteⅣ,and the elastic stiffness of spring K as 10000 kN/m in siteⅠ0,50000 kN/m in siteⅡ,and 100000 kN/m in siteⅣ.展开更多
基金Ministry of Science and Technology of China Under Grant No. SLDRCE09-B-08Kwang-Hua Fund for College of Civil Engineering, Tongji Universitythe National Natural Science Foundation of China Under Grants No.50978194 and No.90915011
文摘During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.
文摘The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce some high-tech dynamic control devices to reduce dynamic response for double-deck cable-stayed bridges under earthquakes.A(90+128)m-span double-deck cable-stayed bridge with a steel truss beam is taken as the prototype bridge.A 3D finite element model is built to conduct the nonlinear time-history analysis of different site categories in fortification intensityⅨ(0.40 g)degree area.Two new types of dynamic control devices-cable sliding friction aseismic bearings(CSFABs)and elasticity fluid viscous dampers composite devices(EVFDs)are introduced to reduce the dynamic responses of double-deck cable-stayed bridges with steel truss beam.The parametric optimization design for the damping coefficient C and the elastic stiffness of spring K of EVFDs is conducted.The following conclusions are drawn:(1)The hybrid support system by EVFDs and CSFABs play a good function under both seismic and regular work,especially in eliminating the expansion joints damage;(2)The hybrid support system can reduce the beam-end displacement by 75%and the tower-bottom bending moment by 60%under the longitudinal seismic excitation.In addition,it can reduce the pier-bottom bending moment by at least 45%under transverse seismic and control the relative displacement between the pier and beam within 0.3 m.(3)Assuming the velocity indexα=0.3,the parametric optimization suggests the damping coefficient C as 2000 kN·s·m-1in siteⅠ0,4000kN·s·m-1in siteⅡ,6000 kN·s·m-1in siteⅣ,and the elastic stiffness of spring K as 10000 kN/m in siteⅠ0,50000 kN/m in siteⅡ,and 100000 kN/m in siteⅣ.
