Abstract
Progressive collapse, the extensive or complete collapse of a structure resulting from the failure of one or a small number of structural components, has become a focus of research efforts and design considerations following events occurring at the Ronan Point apartment building in London, the Murrah Federal Building in Oklahoma City, and the World Trade Center in New York City. A principle research and design area for progressive collapse investigates the behavior of structural frames when column support is removed. The mechanism that results from loss of column support in structural frames characteristically involves beams that are unable to provide sufficient flexural resistance. Cable retrofit is one method to enhance existing frames and supplement or replace the post-mechanism beam load resistance with straight-legged catenary resistance after a column removal. The cables are located linearly along the beam geometry and are affixed at beam supports. This paper investigates both static and dynamic behavior of the catenary action of retrofit cables, which include both the linear and nonlinear material behavior of the cable material. Moreover, a simplified model serves as the basis for retrofit cable design is presented. Finite element modeling and experimentation in this paper verify and validate the applicability of the model. Finally, a framework for developing a procedure for retrofit cable design is presented.
Highlights
Catenary behavior plays a significant role in the behavior of structural elements resisting loads capable of causing progressive collapse [1,2,3,4,5,6]
The modified catenary model presented in this paper is an efficient, applicable tool that can be used to understand the fundamental mechanisms present in catenary scenarios in which mass is lumped to a central position and flexural resistance is small
As expressed in Equation (11), geometric nonlinearities in modified catenary systems in the elastic material range result in load carrying capacity that is approximately proportional to the cubic displacement
Summary
Catenary behavior plays a significant role in the behavior of structural elements resisting loads capable of causing progressive collapse [1,2,3,4,5,6]. In instances of “small” initial variations from horizontal (i.e., shallow modified catenary), truss analysis is not appropriate and nonlinear geometry must be considered Forms of this shallow modified catenary can be seen in several structural applications: progressive collapse retrofit [23,24], progressive collapse resisted by concrete reinforcement [9,20], overhead wires for electric rail [25,26], and ice loads and wind-on-ice loads on electrical power lines [27,28]. This paper assumes that the retrofit cable is required to transfer the entire load This (M.C.) model provides a fundamental understanding of the stiffness of the catenary throughout the static load-deflection behavior and incorporates this stiffness in nonlinear dynamic analyses. An illustrative application of the M.C. model cable retrofit design is presented
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