Protection performance of stiffener-enhanced steel-concrete composite sacrificial cladding with foamed geopolymer core subjected to impact loads

Abstract

In this study, a novel composite sacrificial cladding (CCES) for structural protection against impact loads is proposed, comprising a steel-concrete composite face panel enhanced with stiffeners (CFPES) and a foamed geopolymer (FG) core. First, to explore the protection performance of CCES, drop-weight impact experiments were conducted on integral back plates (IBP, considered as the protected structure) with or without CCES protection. The results show that incorporating CCES promotes a transition in the damage pattern of IBP from local indentation to overall flexural, reducing its central residual deflection by 34%. Subsequently, the effects of the face panel type, connection configuration, and stiffener spacing were further explored with the experimentally verified numerical model. For a fair comparison on an equivalent-mass basis, the proposed CFPES is numerically compared with conventional methods for improving the stiffness of sacrificial cladding panels, including increasing the thickness of the steel face panel and using composite face panels with different connection configurations (e.g., thickened steel plates, embedded reinforcement mesh, or bolted panels). The numerical results show that the proposed CFPES provides favorable protection performance with substantially reduced residual deflection. This is primarily attributed to the more pronounced stiffness enhancement achieved by the CFPES, in which the vertical stiffeners provide an effective mechanical connection between the upper and lower steel plates and simultaneously impose stronger confinement on the infilled concrete. As a result, localized deformation of CFPES is effectively suppressed, contributing to more uniform compression of the underlying FG core. Consequently, the numerical results demonstrate that CCES with CFPES exhibits more favorable protective performance in terms of damage extent, energy absorption, and load mitigation, particularly at a relatively high impact velocity of 15 m/s. Additionally, by avoiding localized deformation of the top and bottom steel plates caused by excessively large stiffener spacing, while simultaneously preventing local buckling of stiffeners induced by overly small stiffener spacing, CFPES with a moderate stiffener spacing ratio (0.083-0.091) shows favorable protective performance. Specifically, the transmitted impact energy to the IBP and the maximum transmitted load are reduced by up to 74% and 30%, respectively, even at an impact velocity of 15 m/s. These findings indicate that incorporating a high-stiffness CFPES is a promising strategy for enhancing the protective behavior of CCES, while also offering a useful reference for its future practical engineering application.