Damage evaluations of fire-damaged RPC-FST columns under blast loading

Abstract

Reactive Powder Concrete-Filled Steel Tube (RPC-FST) is a new composite section with ultra-high strength, good plasticity and ductility to withstand blast loading. This paper is devoted to introduce an analytical method for evaluating the damage level of RPC-FST column suffered fire attack and the following blast load. The damage indexes of RPC-FST column has experienced ISO-834 standard fire and subsequent blast load are predicted using Pressure-Impulse (P-I) diagram. The analytical approaches are proposed based on equivalent Single Degree of Freedom (SDOF) model, in which the damping dissipation, thermal effect and axial load are included. In order to clarify the influences of temperature distribution and explosive charge on the damage index, an inclusive P-I function, characterized by three variables: pressure, impulse and fire duration, is presented. Then blast-resistant results of four fire-damaged RPC-FST columns are employed to validate the reliabilities of presented method. Parametric analysis is conducted to investigate the impacts of damping ratio and ductility ratio on the structural damages. It is demonstrated that a larger damping would lead to better structural blast-resistance. The asymptote value of quasi-static zone tends to smaller as the ductility ratio increases, either the asymptote value of impulse zone, which results in a larger safe area for structural member. In addition, the damaged level is governed by impulse load as scaled distance decreases. The analytical damage indexes are well validated by experimental data.