Date

1-1-2018

Document Type

Thesis

Degree

Master of Science

Department

Structural Engineering

First Adviser

Spencer E. Quiel

Abstract

Progressive collapse requirements are often prescribed for the design of facilities occupied by U.S. federal agencies or providers of critical services. Notional removal of load-bearing elements throughout the perimeter frame is a common approach that is used to implicitly strengthen the structure in order to resist collapsing when damaged by blast or impact threats from outside the building. Many of these facilities are midrise buildings and are commonly designed for progressive collapse resistance using structural steel due to high ductility and favorable strength-to-weight ratio. This study considers several framing designs for a prototype midrise steel building that are designed first for conventional gravity, wind, and seismic loads and then enhanced to meet progressive collapse requirements. Two iterations of the MRF, which is commonly used for progressive collapse resistant steel buildings, are designed to different levels of allowable plastic deformation per current seismic design criteria. Two systems utilizing continuous trusses are considered: one using a hat truss above the roof and another with a belt truss located within the top story. The diagrid is designed using a multi-story inclined module which was selected to increase load-bearing efficiency in a progressive collapse scenario. The results of this study compare the structural performance and cost-benefit (measured in terms of steel weight and connection requirements) of each design when resisting a nominal removal of load-bearing elements per current progressive collapse resistant design criteria. The MRFs typically experience larger levels of plastic deformation, but the truss systems and diagrid structure demonstrate the ability to redistribute loads over a wider region of the perimeter structure. The truss and diagrid structures also tend to offer similar performance to the MRFs with less weight though potentially with greater quantity and complexity of connections.

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