A New Hybrid Input Strategy to Reproduce Across-Fault Ground Motions on Multi-Shaking Tables

Extended engineering structures such as bridges, tunnels, and pipelines are vulnerable to surface fault ruptures, and thus large-scale tests using multi-shaking tables are necessary to investigate the structural performance in this special scenario. Because of the properties of the conventional displacement-controlled shaking table system with proportional-integral-derivative controllers, acceleration and displacement input strategies have respective drawbacks when used to reproduce across-fault ground motions. This study presents a new hybrid input strategy to reproduce across-fault ground motions on multi-shaking tables, which overcomes the limitations of traditional acceleration or displacement input. In particular, the new input strategy aims to match both low-frequency displacements and high-frequency accelerations. The proposed hybrid input strategy was validated by the previously performed shaking table tests of a steel-concrete composite rigid-frame bridge under the across-fault ground motions. For comparison, conventional acceleration and displacement input strategies were also used in the tests to excite the bridge model. Test results including the reproduced ground motions and the structural responses obtained by the three input strategies are presented and compared. The test results indicate that the proposed hybrid input strategy can reproduce across-fault ground motions with improved fidelity on conventional multi-shaking tables. This study can provide useful references for the shaking table tests of bridge, tunnel and pipeline structures with the consideration of crossing fault-rupture zones.