QUANTIFYING INHERENT ROBUSTNESS. IN STRUCTURAL STEEL FRAMING SYSTEMS

Christopher M. Foley1, Kristine Martin2 and Carl Schneeman3

IMarquette University, Haggerty Hall 267, 1515 W. Wisconsin Ave., Milwaukee, WI53233, USA,

E-mail: chris. foley@marquette. edu

2Marquette University, Currently: Framatone ANP, Inc., Naperville, IL 60563, USA
3Marquette University, Currently: Walker Parking Consultants, Minneapolis, MN 55416, USA

Introduction

It is well known that Vierendeel action in multi-story steel frames can be a source of inherent robustness and will provide a significant measure of general structural integrity in structural steel moment resisting framing systems. In situations where there is insufficient number of stories above a compromised column, or when simply-connected floor framing is assumed as in the case of most modern steel framing systems, the robustness inherent in the system remains to be fully understood. Grierson et al. (2005) points out those progressive collapse scenarios in steel structures that begin with upper-story columns becoming ineffective. The collapse sequence associated with these scenarios is a propagation of failures down the structural system to the ground level through debris loading accumulation.

Many analytical efforts to date only consider components found in the structural steel skeleton. Furthermore, the analytical models assumed that pin-connected beams and girders existed at interior columns and these analytical models did not support analysis considering ineffective interior columns, interior girders, exterior girders, or in-fill beams. If robustness in the structural steel framing system is to be quantified, the analyses must go beyond the simple removal of columns around the perimeter of the framework.

The objectives of this paper are to provide a brief overview of the methodologies that have been proposed and validated via experimental testing for quantifying the catenary and membrane mechanisms in concrete floor framing systems; and outline a new methodology for quantifying the membrane and catenary capacity in structural steel floor framing systems along with high-level provisions for ensuring structural integrity through the preservation of catenary and membrane action.