Dynamic coefficient analysis of enhanced plastic resistance beams under Friedlander-type blast loading

Compared to alternative blast loading formulations, the Friedlander-type loading function effectively captures the attenuation characteristics inherent in explosive pressure-time histories, making it extensively adopted for validating blast loading effects on structures. This empirical model also demonstrates significant potential for enabling refined blast-resistant design methodologies in structural engineering. Furthermore, beam components have gained widespread application in protective structural systems due to their inherent energy absorption capacity and load redistribution mechanisms under blast-induced dynamic loading conditions. Considering the enhanced plastic resistance characteristics of beam components, this study investigates the variation of the dynamic coefficient of beam components under Friedlander-type blast loading. The motion differential equations for both flexible and rigid beam components at different stages are derived using the equivalent single-degree-of-freedom (SDOF) method. The results of dynamic coefficient calculations under 27 typical loading conditions are presented. The displacement response of I-shaped steel beams under Friedlander-type blast loading for different conditions is simulated using the finite element software LS-DYNA. The theoretical results are then compared with finite element and code-based calculations, validating the feasibility of the proposed theory through multiple methods. The research findings indicate that the finite element method results align well with the theoretical results derived from the Friedlander-type loading model. The current blast-resistant design code is more applicable to flexible beam components, while it shows significant discrepancies for rigid beams, which could hinder blast-resistant design. Both the resistance enhancement factor and the Friedlander-type loading shape parameter reduce the dynamic coefficient, with the latter exerting a stronger influence on the dynamic coefficient than the resistance enhancement factor.