Experimental study on the residual axial capacity of ultra high performance cementitious composite filled steel tube (UHPCC-FST) column under contact explosion

摘要

Ultra-high performance cementitious composite filled steel tube (UHPCC-FST) has been widely applied as the load bearing members for long-span bridges, which are the potential bomb explosion attack targets in terroristic activities. This paper aims to experimentally study the residual axial capacity of UHPCC-FST columns under contact explosion by conducting the field contact detonation and the subsequent axial compression tests. Firstly, five UHPCC-FST cylinder columns are fabricated with the column height, outer diameter and core concrete compressive strength being 2000 mm, 203 mm and 131.5 MPa, respectively. Secondly, three of which are tested under contact explosion with the TNT charge weights of 1 kg, 2 kg and 3 kg, in which the impact craters are formed and the integrity of the columns is maintained under 1 kg and 2 kg TNT explosions, while the outer steel tube is seriously ruptured and the core UHPCC is fully crushed for 3 kg TNT explosion. Furthermore, the original axial capacity of intact columns and the residual axial capacity of blast-damaged columns are evaluated though the axial compression tests, and the relationships between the axial load and axial/lateral displacement are derived. It indicates that, (i) both the intact and blast-damaged columns under axial compression show diagonal shear failure, the local bulging of steel tube is induced due to the low confinement of steel tube and high compressive strength of UHPCC; (ii) the quantitative dependence of column damage index on the charge weight is determined.