Study On Transverse Displacement Control Of Simply-supported Bridges Supported By Laminated Rubber Bearings Under Ground Motions

Small and medium girder bridges plate type elastomeric pad bearings are widely distributed in China,this type of bearing is usually directly on the stone pier,there is no fixed measures between the bearing and the cushion stone,main girder,only through the contact surfaces of friction to prevent the occurrence of the three relative displacement,usually set in reinforced concrete retainers on both sides of the cap or grider to enhanced horizontal contact structure.This kind of bridge under strong earthquake are often in the transverse direction of the bridge are severely damaged,the specific performance of the reinforced concrete retainer is cut off,transverse displacement of girder is too large,bearing damage,so the transverse displacement of bridge control has become a hotspot at home and abroad.In this paper,a series of systematic studies are carried out on the transverse displacement control method of the plate type rubber beam bridge.1?Taking the Minjiang River Bridge as an example which seriously damaged in the Wenchuan earthquake,the whole process of bridge damage is systematically demonstrated by IDA method,and the damage state and damage index of support and pier are evaluated.The main conclusions are as follows:(1)The displacement of the main girder and the deformation of the support increase with the increase of PGA,in which the support is gradually transited from the non damage state until serious damage or complete damage occurs;(2)The internal force response of the pier increases with the increase of PGA when the PGA is not large.When the PGA is large,the internal force response of the pier increase very slowly,and the pier only has slight damage.2?Through the arrangement of the reinforced concrete retainer of Yingxiu Minjiang Bridge carried out a series of transverse displacement control research,focuses on the research of reinforced concrete retainer retaining strength parameters and deformation parameters,retainer and grider gap parameters and the friction coefficient parameters under different grider transverse displacement response,bearing deformation,internal force response and the response of bridge pier the mechanical properties of the retaining retainer,the main conclusions are:(1)The traditional reinforced concrete retainer as the structure itself causes the seismic capacity is limited,it will serious damage under the earthquake,whether improve the strength of retainer or change the deformation ability of the retainer or i ncrease gap with the main grider are not makes the transverse displacement of bridge get better control;(2)Set the reinforced concrete retainers increase the seismic response of the pier,the internal force response improves of the pier with the strength and deformation of the retainers increase,while increase the retainers gap get eased,although with the bearing friction coefficient increase the displacement of girder and bearing deformation have certain restrictions,but the " burden" of the pier increased;(3)Through comprehensive analysis,put forward reasonable design method of reinforced concrete retainer,while the strength of the retainer is constant load force 20% of each pier bearing,deformation of the retainer is 0.1,retainer and grider gap is 6cm,the friction coefficient is 0.2,reinforced concrete retainer comprehensive resist earthquake effect is best.3?A series of tranverse displacement control research on Yingxiu Minjiang River Bridge by setting elastic-plastic steel shear key.Focus on the strength parameters of the elastic-plastic steel shear key,initial stiffness parameters,stiffness parameter after yield and bearing friction coefficient parameter under different grider displacement response,bearing deformation response and internal force response and the mechanical properties of the pier retainer,the main conclusions are:(1)Compared with the no retainer or reinforced concrete retainer,the elastic-plastic steel shear key effectively control tranverse displacement of the bridge,and the limit effect is very ideal;(2)Improve the strength of elastic-plastic steel shear key,initial stiffness and stiffness parameter after yield makes the tranverse displacement of bridge is further reduced,this also increases the internal force response demand of bridge piers,the friction coefficient has no effect on controlling the tranverse displacement of the bridge;(3)After a comprehensive analysis put forward reasonable design method of elastic-plastic steel shear key,while the strength of the retainer is constant load force 20% of each pier bearing,initial force stiffness of a pier bearing shear stiffness and 5 times,yield stiffness 1%,bearing friction coefficient is 0.15 elastic-plastic steel shear key resist earthquake effect is the best.