Blast and Impact Resistant Design of Overhead Protection Structures

Overhead protection (OHP) structures are used by major oil operators and government agencies in terrorist affected areas to protect facilities housing their personnel such as office facilities and dining facilities. Structural design of OHP structures to resist blast/fragment loads by 120 mm mortars and rockets is presented in this paper. The OHP structure consists of two layers: a pre-detonation layer and a shielding layer. The pre-detonation layer consists of plywood supported by steel beams, and this will cause the ordnance to explode upon impact. The shielding layer underneath consists of steel plates and sand bags supported by steel frames. The sand bags are intended to stop the fragmentation of the mortars or rockets while the steel plates and the supporting structural frames will resist the blast and impact loads. The blast and fragment loads caused by 120 mm mortar and rockets were calculated, and the required plywood thickness and sand bag thickness were determined. A finite element model for the OHP structure was developed using the general-purpose finite element program ABAQUS/Standard, and the structure was evaluated for the blast loads using the procedures in 2010 ASCE Guidelines, “Design of Blast Resistant Buildings in Petrochemical Facilities”. In addition, the OHP structure was also evaluated for normal design loads such as wind loads and seismic loads based on 2006 International Building Code.

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