Capacity Spectrum Method Considering SSI Effects For Beam Bridge Under Near-Field Earthquake

The beam bridge is the most common bridge type in use in our country, and the security of the beam bridge under strong ground motions is worth paying attention to. Besides, near-field ground pulse-type ground motions and solid-structure interaction(SSI effects) are major issues relating to seismic design of bridges. Therefore, based on previous research, a modified capacity spectrum method considering SSI effects for beam bridge under near-field earthquake is put forward in this paper.In this paper, the main research works are as follows:1. A large amount of data of near-field ground motion records is collected. The influence of characteristics of ground motions and restoring force model parameters on elasto-plastic response spectrum for near-field ground motions is investigated. The qualitative analysis of near-field seismic design spectrum in UBC97 is also carried out. Then the elasto-plastic response spectrum for near-field earthquake corresponding to Specification of Seismic Design for highway Engineering is established, which provides the demand spectrum for the capacity spectrum method suggested in this paper.2. A capacity spectrum method considering SSI effects for beam bridge with middle piers or low piers under near-field earthquake is proposed, and a practical example of a beam bridge with middle piers is provide to demonstrate the calculation process of this method. In addition, a comparison among computation results of this method with time-history analysis method as well as equivalent linearization procedure in FEMA440 is discussed, thus verifying the feasibility and necessity of applying this method to seismic performance evaluation of beam bridges under near-field earthquake.3. A capacity spectrum method considering higher modes and SSI effects for beam bridge with high piers under near-field earthquake is suggested, with MMPA method considering higher modes supplied. Besides, this method is applied to seismic performance evaluation of a beam bridge with high piers, and influence of such factors as higher modes, foundation flexibility effects and foundation damping effects on computation results of method is also discussed.In conclusion, with near-field earthquake and SSI effects taken into consideration, an improved capacity spectrum method is presented, which can provide valuable reference for seismic performance evaluation of beam bridges.