Steel-Plate Composite Walls Subjected to Missile Impact: Experimental Evaluation of Local Damage

This paper presents the results of an experimental program conducted to evaluate the local damage behavior of steel-plate composite (SC) walls subjected to missile impact. There is significant interest in the use of SC walls for protective structures particularly to resist impactive and impulsive loading. The behavior of SC walls subjected to these loads differs from that of reinforced concrete (RC) walls due to the placement of steel plates on the surfaces, which prevents concrete scabbing and enhances local perforation resistance. The results from the experimental program are used to demonstrate and explain progression of damage modes leading to local perforation, and to validate and quantify the conservatism of a recently developed design method. Laboratory-scale SC wall specimens were fabricated and tested in an indoor missile impact facility specially built and commissioned for this research. Sixteen tests were conducted with varied parameters: the steel plate reinforcement ratio ($\rho :3.7\%–5.2\%$); tie bar spacing, size, and reinforcement ratio (${\rho }_t:0.37\%–1.23\%$); steel plate yield stress ($f_y^{nom}:\mathrm{Gr}·50–\mathrm{Gr}·65$); and missile diameter ($D_m:25.4$, 38.1 mm), weight ($W_m:0.59$, 0.91, 1.59 kg), and velocity ($V_m:125–232\mathrm{m}/\mathrm{s}$). Experimental results include the measured missile velocity, penetration depth, rear steel plate bulging deformation, and test outcome (stopped or perforated). The observations of behavior and progression of damage (missile penetration and local perforation) are used to quantify and explain the sources of conservatism in the design method, which include the dimensions of the concrete conical frustum (breaking out) and the assumed penetration depth equations.