Multi-point shaking table test for long tunnels subjected to non-uniform seismic loadings – Part I: Theory and validation

The spatially varying ground motions can significantly influence the dynamic response of extended structures such as tunnels. However, current knowledge on the effects of non-uniform seismic excitations on long tunnels is limited to analytical or numerical methods and lack of experimental or field data. This paper presents a confirmatory experimental method for long tunnels subjected to non-uniform excitations, using four independent shaking tables worked in coordination as a large linear shaking table array. The discrete multi-point input mechanism is deemed critical to accomplish a continuous and coordinated excitation over a long tunnel. A 40 m-long segmental model container is developed to realize the equivalent transformation from the four independent shaking tables into continuous excitations. The dimension of the segmental model container as well as the connection between each of its components is determined after significant analytical and numerical simulations. A series of tests are conducted to investigate the wave passage effect along the length of the segmental model container. Results show that the wave passage effect is accurately reproduced with the test setup and the acceleration input scheme, and thus the validation of the design of the multi-point test system is approved.