Shaking Table Test Study On Seismic Response Of Underground Structures Subjected To Non-uniform Earthquake

As the functionality of underground structures continues to increase,the scale of underground structures also tends to become larger,such as some urban rail transit stations,hub stations,and vehicle depots.For large-scale underground structures with large scales,seismic waves reach different positions on the structure there is a difference in the time at which the impact of non-uniform seismic excitations such as the traveling wave effect cannot be ignored.Therefore,it is necessary to study the seismic response of underground structures under non-uniform excitation through shaking table tests.In order to carry out non-uniform seismic action shaking table tests,the theoretical derivation and related verification of the traveling wave input test method for a single shaking table were completed,and a multi-segment model box that can be used for multi-point shaking table tests was designed to complete consistent/non-uniform earthquakes.The design of the shaking table test scheme for the structure of the free-field and cross-interchange station under the action,and the numerical model of the free-field test data was used to verify the rationality of the numerical method.Then a numerical model of the structure of the free-field and large cross-interchange station was established.Compare and analyze the seismic response laws of uniform waves,traveling waves,coherent waves,coherent traveling waves and multidirectional ground motions,and analyze the scope of their spatial effects.Based on the calculation results of this article,the following conclusions can be drawn:（1）For the free field,after the local surface distance is greater than 405m,the amplification effect of the traveling wave on the surface acceleration exceeds the uniform wave,while the amplification effect of the coherent wave and the coherent traveling wave on the surface acceleration response are significantly smaller than the uniform wave.And as the height increases,the high-frequency components in seismic waves are significantly reduced,while the low-frequency components are amplified to a certain extent,and the influence of different soil layers on their frequency components is different.（2）The existence of the cross-exchange station structure will reduce the surface acceleration response to a certain extent.For soil outside the end wall,the maximum impact range is 54m,which is 2B₁（B₁ is the station width of the seismic wave input direction 27m）.For the seismic response of the transfer station structure,in the station structure along the input direction of the seismic wave,after the station structure is larger than 405m,the acceleration response under the action of the traveling wave is greater than the uniform wave.Under the action of coherent waves and coherent traveling waves,its acceleration response is much smaller than that of uniform waves.For the station structure perpendicular to the direction of seismic wave input,the uniform wave and traveling wave are more sensitive to the acceleration response of the structure,while the coherent wave and coherent traveling wave are more sensitive to the structural bending moment.（3）For horizontal two-way ground motion input,there are significant differences in the degree of influence of seismic waves in different directions on the response law of different parts of the station structure.For three-way input,the effect of vertical seismic waves on the structural acceleration response is extremely significant,but its bending moment and relative displacement are still mainly affected by horizontal two-way seismic waves.（4）The maximum range of the spatial effect of the transfer station is:5B/3（close to the transfer node）and 4B/3（close to the end wall）,where B is the width of the station structure 54m,and the effect of multi-directional input on the spatial effect is small.