Seimic Fragility Analysis Of Continuous Beam Bridge With Short Pier Using Pot Rubber Bearing

Due to terrain reasons and engineering needs,short piers with shear span ratio less than 2.5 are often used in mountainous bridges and urban ramp bridges.Many earthquake damage investigations show that reinforced concrete short piers are prone to shear failure.The use of seismic isolation bearings can effectively extend the vibration period of the bridge,reduce the shear force of the pier during the earthquake,and avoid brittle failure of the pier.The failure mode of the short pier bridge with seismic isolation design in strong earthquake and the failure probability of each fragile component under different intensity earthquakes need to be further studied.In this thesis,the Zamora Bridge,which was destroyed in 2019,is taken as the engineering background.It systematically studies the seismic fragility of the fragile components and the whole bridge system of the short pier continuous beam bridge with pot rubber bearing.It provides reference for seismic design of similar bridges.The main research contents of this thesis are as follows :(1)The thesis summarizes the research status of seismic resistance of reinforced concrete short pier and seismic fragility of bridge structure,and forms a complete set of seismic fragility analysis process of short pier continuous beam bridge,which provides a theoretical basis for the later research.(2)In the Pacific Earthquake Engineering Research Center,10 ground motions of class II sites were selected,and the uncertainty of five structural parameters was considered.A total of 100 ground motion-structure analysis samples were established by Latin hypercube sampling.The finite element model of the structural analysis sample is established by Open Sees finite element software,and the incremental dynamic analysis of the structure is carried out to obtain the nonlinear seismic response of each fragile component of the structural sample under different intensity earthquakes.(3)The article defines the ultimate damage states of parameters such as pier bending resistance,pier shear resistance,relative displacement of pot rubber bearing,shear resistance of anchor bolts and horizontal bearing capacity of supporting padstone under earthquake action.And it calculates the boundary values of the above damage parameters under different states.These research works provide the basis for structural seismic vulnerability analysis.(4)The thesis systematically studies the seismic fragility of bridge piers,pot rubber bearings,supporting cushion stones and anchoring bolts under the action of along-bridge and cross-bridge ground motions under different intensity earthquakes.The results show that under strong earthquakes,the short pier continuous beam bridge with pot rubber bearings is more likely to be damaged than the bending failure and shear failure of piers,the bearings,supporting padstones and anchor bolts.Attention should be paid to the seismic design of such bridges.(5)Based on the seismic fragility analysis of components,the seismic fragility analysis of the whole bridge system is carried out by using the first-order reliability theory,and the damage probability of the whole bridge system under different damage states is obtained.