Performance-based blast-resistant design of RC bridge piers under vehicular bombs

Bridge piers are the critical components to support the superstructures and the blast resistance of piers has attracted extensive attention considering the ever growing deliberate and accidental explosion attacks on bridge structures. However, most of the existing studies focus on the blast-induced dynamic response of a single pier without considering the bridge redundancy, even less the actual traffic performance of the entire bridge. This paper aims to propose a performance-based blast-resistant design approach of RC bridge piers under explosions of vehicular bombs. Firstly, the distribution model of blast impulse on bridge piers is proposed with considering both the ground reflections and diffractions of piers based on the validated finite element analysis (FEA) approach. Then, the fiber beam element-based model and the above blast impulse distribution model were validated based on the dynamic monotonic loading test and the explosion test on RC frame column. Furthermore, the simplified fiber element beam-based prototype RC bridge was established and the parametric studies were performed. Finally, the response surface methodology was adopted and the performance-based blast-resistant design procedure for three design basis threats specified in FEMA, i.e., cargo van bomb, small moving van bomb, moving van bomb, was proposed with utilizing the relative vertical displacement of the mid-bent as the performance index. It derives that, (i) the proposed distribution model of blast impulse is applicable to explosions at scaled distances of 0.5-2.1 m/kg1/3; (ii) the fiber beam element-based model can well describe the global response of the blast-exploded columns/piers; (iii) the proposed performance-based blast-resistant design approach can provide an efficient tool for bridge engineers.