EVALUATION ON SEISMIC RETROFIT MEASURES FOR COMMON UTILITY TUNNELS BASED ON CYCLIC LOADING TESTS

Abstract

Since common utility tunnel is very lightly reinforced without cross bars between inner and outer bars, it is vulnerable to the seismic effects. Effectiveness of seismic retrofit was clarified based on cyclic loading tests on six specimens. They are prototype models at the side wall connected to the lower slab joints. Full penetration anchor bolts and bolts with a special device which enables to anchor at mid wall height were used to confine the concrete and prevent shear failure. Carbon fiber reinforced plastic sheets were also used in the retrofit. Number of CFRP sheets and anchor at the slab was varied. It was found from the experiment that the as-built tunnel failed in shear at the wall-slab joint. The retrofit by bolts and CFRP is effective to enhance the shear capacity and ductility.