Experimental studies on residual carrying-capacities of fire and blast-damaged RPC-FST columns

An equivalent Single-Degree-of-Freedom (SDOF) model is developed to predict the residual carrying-capacities of fire-damaged Reactive Powder Concrete-Filled Steel Tubular (RPC-FST) columns under axial lateral blast loadings. The initial deflections of fire and blast-damaged RPC-FST columns are derived by the proposed SDOF model, then the residual carrying-capacities and damage levels are further obtained based on the unified theory of Concrete-Filled Steel Tubular (CFST) members. The residual carrying-capacities of fire and blast-damaged RPC-FST columns are investigated by a series of large-scale blast-resistant tests, in which the influences of scale standoff distance and fire duration on residual carrying-capacities and failure modes are discussed. Experimental results show that the analytical results of residual load capacities and damage indexes are well validated by experimental data. The residual carrying-capacities of RPC-FST columns decreased by 16%-67%, it means that the carrying-capacities would seriously degraded by fire and blast attacks, but it is more sensitive to fire duration than that to blast loading. It is indicated that the residual carrying-capacities of RPC-FST columns only experienced 105 min fire attack decrease by 60%, and only suffered blast loading decrease by 16%.However, the residual carrying-capacities of RPC-FST column suffered fire attack and following blast load would decrease by 67%. The damaged assessments of 5 RPC-FST columns indicate that one specimen is lightly damaged, two specimens are moderately damaged, and two specimens are severely damaged, respectively. The good performance for the fire- and blast- resistances of RPC-FST columns are experimentally verified.