Finite Element Modelling of Large Area Maintenance Shelters and Comparison to Experimental Results

Abstract

Large area maintenance shelters (LAMS) are used as temporary structures by the United States Air Force to provide shelter for helicopters, tanks, wheeled vehicles, and aircraft. There are several different brands of LAMS used throughout the military, however the one focused on in this study is specifically used by the Air Force. These structures are lightweight and easy to construct, take down, and ship and are used throughout the world on military bases by the United States Air Force. However, several of these shelters have experienced failure due to wind loads below those the structure was designed to withstand. The objective of this study is to investigate the structural response of a typical LAMS to design wind load cases and identify any systemic factors that may be contributing to premature failure. In this study, the structure is modeled using SAP 2000. Simple load cases were applied to understand the vertical and lateral load paths through the structure. Design wind loads were then developed and applied to the structure. Modeled demands under design wind loads were compared against preliminary strains, forces, and displacements measured in-situ in an existing, instrumented LAMS. The comparison demonstrated mixed agreements between the model output and responses of the in-service LAMS under transverse and longitudinal wind loads. Finally, the design wind loads were used to analyze the maximum demands on the structure. Some stresses within the model were found to be larger than the allowable stress. This was the case at the eave of the windward door frames under longitudinal wind loads. The failures that have occurred in several LAMS show similar mechanisms and locations. The high uncertainty of the wind loads on the door frames, along with the uncertainty of the tightness of the cables, purlins, and fabric could all be contributing factors to these failures.