Analysis and design of reinforced concrete wall systems for blast

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Building envelope is the first and most critical line of defense for a structure against external explosion. Building envelope can be divided into two categories; structural and non-structural. Non-structural types of building envelope, which are generally non-load bearing, are intended to enclose the building, and thus are conventionally designed to resist minimal lateral loading. Various ductile sheet materials are currently used to retrofit existing concrete wall systems to mitigate the effects of external blast. Sheet retrofits can increase the strength and ductility of the wall and provide a means of fragmentation control. The use of insulated precast/prestressed concrete and insulated tilt-up concrete sandwich panels for exterior walls is common practice. These forms of construction provide a thermally efficient and high-mass wall that enhances the energy efficiency and blast resistance of the building making it ideal for military and government facilities. Current design recommendations are very restrictive when using these forms of construction, due in large part to the lack of experimental research data. To develop blast design guidelines for wall systems, it is necessary to develop experimentally verified static resistance functions. In this dissertation, several concrete panel systems were experimentally and numerically analyzed, including concrete walls with different sheet retrofit systems and different sandwich panels (SWP's). A series of 15 retrofit panels and 35 SWP's were evaluated. The static performance of the wall systems subjected to uniform pressures will be presented. Nonlinear 3D Finite Element Models (FEM), analytical models and single degree of freedom (SDOF) analyses were performed to analyze the static and dynamic response of the wall systems. The developed models showed good correlation with the experimental results.Static resistance functions were developed for various types of sheet retrofits and reinforced concrete slab using a mechanics of materials approach. The individual analytical models for the sheet and reinforced concrete slab were then combined to develop a static resistance function for the concrete-sheet retrofit systems. The analytical model using layered beam approach combined with the plastic hinge proposed in this dissertation compared well with the experimental results for the SWP's. The SWP results indicate that such wall systems provide blast resistance over a large deformation range making these systems useful for blast protection applications. The responses of the SWP's were found to be sensitive to reinforcement type, shear ties used, and insulation. Various retrofit systems for concrete slabs were experimentally evaluated and analytically modeled in this project. Retrofits with a higher stiffness proved more difficult to analytically model but provided the greatest increase in energy absorption. Flexible retrofits provided a smaller increase in energy absorption and did not fail at large support rotations. All retrofits exhibited significant energy absorption after a support rotation of 10 degrees.