Evaluation of seismic behavior of box culvert buried in the ground through centrifuge model tests and numerical analysis

摘要

Japan has yet to establish a seismic design for road box culverts (RBCs) because past major earthquakes did not damage them. In recent years, structures with enlarged sectional dimensions (the purpose of which is to optimize the internal space in RBCs) have become common. However, the unknown seismic strength of such large RBCs makes RBC seismic designs increasingly necessary. Several seismic design methods have been developed for and applied to rectangular underground structures, e.g., cut-and-cover tunnels, which are structurally similar to RBCs. Although these methods are applicable to RBCs, it is uncertain whether they can be applied directly because there are currently no evaluation results from model tests on RBCs, which have unique structural features, e.g., no haunch at the bottom of the sidewalls. Therefore, we verify a seismic behavior of an RBC and develop a method for evaluating it in order to establish a seismic design for RBCs. We conducted centrifuge model tests subjected to seismic force and a numerical analysis using an elastoplastic finite analysis method, in addition, we validated this analysis by comparing the test and analytical results. The test results show RBCs will most likely develop rocking rotation when the ground strain exceeds approximately 0.08%. A comparison of the numerical and experimental results shows that this analysis can estimate the shear deformation behavior with approximately 90% accuracy in square cross-section cases. Meanwhile, this analysis has tendency to underestimate the axial forces in each case and to overestimate the bending moments of some members in the case of wide cross-sections.