Experimental study on Y-shaped bridge under 3-dimentional earthquake ground motions

Abstract

Based on similar theory and multi-dimensional seismic design theory, a Y-shaped bridge model with the scale ratio of 1:20 was made to conduct the seismic simulation shaking table test in this paper. Failure mode and dynamic responses of Y-shaped bridge under different seismic wave spectrum, different peak accelerations and different seismic excitation directions were studied. The experimental results show that, the piers mostly exhibit bending failure mode and the vertical ground motion has a great influence on the development of cracks in girders. Dynamic responses of the Y-shaped bridge are different and presented different laws when three different seismic waves were applied. Seismic wave is input along the direction of the branch straight girder, which is the most unfavorable earthquake input direction when calculating the peak acceleration at the top of piers. Multi-dimension seismic excitation should be considered when calculating the width of the expansion joint between adjacent girders. The horizontal bidirectional seismic excitation can satisfy the design requirements of strain response at the bottom of pier. The model structure would cause vertical vibration during its horizontal seismic excitation, and vertical seismic excitation exerts more significant influence on the vertical vibration of branch straight girder.