Experimental Model Studies on the Seismic Response of High Curved Overcrossings,

摘要

An experimental model study relating to the seismic resistance of large multi-span curved overcrossings of the type which suffered heavy damage during the 1971San Fernando Earthquake is reported. The feasibility of developing a model to satisfy the necessary similitude requirements of such a complex structure,and also capable of being tested on the 20ft x 20ft (6.1 m) Shaking Table at the University of California,is outlined. The small amplitude dynamic characteristics of the microconcrete model, a 1/30true-scale version of a hypothetical prototype,are examined and for this elastic range the experimental results compared satisfactorily with those predicted analytically. The response of the model is described for a series of progressively more intense simulated seismic excitations applied (i) horizontally in the asymmestric longitudinal direction,and (ii) horizontally in the symmetric direction,both alone and also with simultaneous vertical excitation. The existence of expansion joints in the bridge deck proved to have great influence on the response of the structure. Despite the inclusion of strong ductile restrainers across these joints,they were subjected to severe damage caused by multiple impacting in both torsional and translational modes. Some recommendations concerning this design are made.