Laminated Glass Curtain Walls and Laminated Glass Lites Subjected to Low-Level Blast Loading

Abstract

Linear elastic and nonlinear elastic analytical investigations are reported for a nearly conventional, laminated glass curtain wall with split screw spline mullions subjected to low-level blast loading. Responses (dynamic stresses, deflections, and accelerations) of the rectangular glass lites within the curtain wall are compared to those of identical glass lites that are (1) simply supported and (2) supported on structural silicone sealant beads along all four edges. The elastic finite element model of the curtain wall was calibrated to small-amplitude static and dynamic experimental results in a previous effort, where effective mullion moments of inertia, connection stiffnesses, and system damping ratios were determined. This calibrated curtain wall model and the two other glass lite models were subjected to uniform blast pressures represented in time by a triangular pulse. These comparisons are made to illustrate the reduction of principal stresses of the glass lites due to the flexibility of the structural silicone bead and, more significantly, the global flexibility of the curtain wall system. Changes in modal frequencies and the appearance or disappearance of significant response modes due to the different boundary conditions of the glass lites are illustrated. For the cases studied, maximum principal stresses were typically halved when the flexibility of the curtain wall members supporting the lite was considered. This paper also shows that: (1) the dynamic behavior of a given glass lite varies dramatically with support conditions as shown in corroborating modal and transient analyses and (2) geometric nonlinearities typically reduce dynamic responses only slightly when compared to linear geometry for the low-amplitude loads considered in this study.