Disaster-resistance Performance Of Coastal Bridges Under Earthquake-tsunami Multiple Hazards

Coastal bridges are important transportation routes for disaster relief and material transportation.Ensuring the safety of coastal bridges under the effects of multiple disasters is of vital significance and role in reducing the loss of life and economic impact as well as accelerating post-disaster recovery and reconstruction.In this paper,the Utatsu Bridge is the prototype,and the shear key and the bearing in the seismic structure facilities are mainly investigated to study the disaster-resistance performance of the classical combination of the bearing and the shear key.Firstly,with considering the mechanical properties of the shear key and the ultimate bearing capacity and deformation of the bearing,the refined finite element numerical model of G8-G10 spans is established.Then the seismic records and the simulated tsunami records of the Utatsu Bridge in the 311 disaster of Japan are used as input to investigate the disaster-resistance performance of the simple supported beam bridge under multiple hazards of earthquake and tsunami.The main conclusions are as follows:(1)Based on the finite element software ANSYA,a numerical model of bridges’ shear key is established to simulate the calculation and analyze its stress mode and failure mechanism.The corresponding structural optimization suggestions are put forward:in order to ensure the maximum strength and the full use of materials,the vertical steel bars designed to bear the shear resistance function should be disconnected at the interface,and the shear steel bars should be reset at the inner side;In the original design,the block cast and formed together with the cover beam can increase the construction joint process and enhance the plastic realization ability of the shear key.it should be noted that the bearing capacity will reduce by about 50%.(2)The finite element modeling and analysis of the rubber pot bearing are carried out.In the modeling of the rubber pot bearing body,the surface contact element connection between the contact surfaces is used to analyze and the material nonlinearity is considered,the accurate results are obtained.The optimization design suggestions for the shear key of dimensions are put forward.(3)With considering the mechanical properties of shear key,bearing and pier,based on Open SEES platform,a finite element model of G8-G10 spans of Utatsu Bridge is established and the numerical analysis is carried out.The simulation results show that under the input of real earthquake and tsunami of the Utatsu Bridge in the 311 disaster of Japan,the bearing slips after the earthquake,resultingin "medium damage" damage,which increases to damage under the subsequent tsunami;After the earthquake,there was a residual displacement of beam body and it failed to return to the original equilibrium position in the subsequent tsunami;the reinforced concrete shear key is seriously damaged,lost the ability of transmitting force,protected the pier from damage,which was basically in good condition.The theoretical analysis results showed that:after the hazards,the piers can still maintain enough strength to prevent its collapse;the beam may float after being submerged,and then be washed away by the tsunami,causing the falling beam.