Methods For Seismic Design Of Simply Supported Beam Bridges Based On Limited Damage To Bearings

Among infrastructure constructions of public transportation in our country, the class B simply-supported beam bridge is widely used because of its simple structure, convenient design and establishment of engineering general figure of standard models. Therefore the seismic safety and maintenance convenience simply-supported beam bridges in important lines is of great importance to the guarantee of smooth traffic network after the earthquake.Through the statistical analysis of seismic damage performance and damage process of simply-supported beam bridges seismic of "5·12" Wenchuan earthquake, it can be known that earthquake damage of plate rubber bearings on the simply-supported beam bridges located in the seismic fortification intensity of VIII or above is hard to avoid, and the percentage of damage of plate rubber bearings is similar to that of displacement of beam, which indicated that the plate rubber bearings’ damage is the major cause of displacement of beam of simply-supported beam bridges. Besides, the plate rubber bearings’damage avoiding the pier damage and fact that the earthquake loss rate of piers is far lower than the other artifacts earthquake loss rate showed the damage of bridge pier is not the main damage of simply-supported beam bridges in the Wenchuan earthquake. Conclusion that the excessive displacement of main girder caused by the damage of bearing failure is most likely to be the the failure path of simply-supported beam bridges was obtained after analyzing the vulnerability.As a consequence, performance-based bearing damage limited seismic design thought and theoretical framework for simply-supported beam bridges were put forward, aiming to protect the bridges by allowing the limited damage of bridge bearings to reduce the dynamic response of bridge piers under high seismic design intensity. Reasonable plate rubber bearings performance targets were raised, combining with engineering practice. Seismic response of the bridge was predicted and appropriate limit measures were taken to limit the bearing damage. With lots of calculation and analysis carried out by the finite element analysis software——OpenSees, the influence of bridge span, environment conditions, bearing friction coefficient and the seismic fortification intensity to bearing were discussed at last. The allowable quantitative bearing damage indicators for B class bridge were proposed after comparing the result with Wenchuan earthquake damage investigation.