Blast Performance of Hollow Metal Steel Doors

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Virginia Tech

Recent terrorist attacks and accidental explosions have prompted increased interest in the blast resistant design of high-risk facilities, including government offices, private sector buildings, transportation terminals, sporting venues, and military facilities. Current blast resistant design standards prioritize the protection of the primary structural system, such as walls, columns, and beams, to prevent a disproportionate collapse of the entire structure. Secondary structural systems and non-structural components, such as blast resistant doors, are typically outside the focus of standard building design. Components such as blast resistant doors are designed and manufactured by private sector entities, and their details are confidential and considered proprietary business information. For this reason, scientific research on blast resistant doors is sparse and most test results are unavailable for public consumption. Nevertheless, the performance of blast doors is crucial to the survival of building occupants as they are relied upon to contain blast pressures and remain operable after a blast event to allow ingress/egress. These important roles highlight the critical need for further research and development to enhance the level of protection provided by components that are often not considered in any detail by protective design practice. This thesis presents a combined experimental and analytical research program intended to support the development of blast resistant hollow metal doors.

A total of 18 static beam-assembly tests were conducted, which consisted of the flexural four-point bending of door segments, to inform on the performance characteristics of full-sized blast resistant doors. Six tests were conducted to evaluate the effectiveness of three skin-core construction methodologies, which consisted of one epoxy and two weld attachment specifications, between door skins and their internal reinforcing structures. The remaining 12 tests were performed to evaluate the in-situ performance of hinge hardware typically installed on blast resistant door assemblies. The results of the skin-core construction tests demonstrated that closely spaced weld patterns would provide the best blast performance. The results of the hinge hardware tests demonstrated that hinges which provided a continuous load-path directly into the primary ii structural core elements of the door frame and door were ideal; furthermore, robust hinges with fully-welded or continuous knuckles were best suited for limiting undesirable deformations.

A semi-empirical analytical methodology was developed to predict the global deformation response of full-sized hollow metal doors subjected to blast loading in the seated direction. The goal was to provide practicing engineers who are competent but non-expert users of high fidelity simulations with the flexibility to conduct in-house evaluation of the blast resistance of hollow metal doors without having to conduct live explosive or simulated blast tests. A finite element analysis was first performed to compute the door resistance function. Hollow metal door construction was idealized using a bulk material sandwiched between sheet metal skins and internally stiffened by stringers. The properties of the bulk material were calibrated such that the deformability of the idealized core reasonably approximated the global load-deformation behavior which occurs due to loss of composite action when welds fail. The resistance curves were then used in a singledegree-of-freedom dynamic analysis to predict the displacement response of the door subjected to blast loading. The proposed methodology was first validated against the static beam-assembly flexural tests. It was then extended to the case of a full-sized door subjected to shock tube blast testing using results published in the literature. The proposed methodology was found to reasonably approximate the out-of-plane load-deformation response of beam-assemblies and full-size doors, provided the bulk material properties of the idealized core are calibrated against experimental data.

Finally, the new Virginia Tech Shock Tube Testing Facility was introduced. A description of the facility, including an overview of the shock tube's location, construction, main components, instrumentation, and key operating principles, were discussed. Operating guidelines and procedures were outlined to ensure safe, controlled, and repeated blast testing operations. A detailed calibration plan was proposed, and future work pertaining to the development of blast resistant hollow metal doors was presented.

Hollow Metal Doors, Blast Doors, Shock Tube, Testing, Finite element method, SDOF analysis, Dynamic, Blast resistant doors