الفهرس 
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Abstract
Progressive collapse (PC) is a phenomenon of local failure of a main structural member
caused by accidental loads, leads to the collapse of the adjacent elements that in turn leads to
global collapse of the structure. Prevention of progressive collapse becomes one of imperative
topics in the structural engineering after the partial failure of Ronan Point in London, 1968.
Nowadays, there are international building guidelines to mitigate the potential of the
progressive collapse. The Unified Facilities Criteria, Department of Defense (UFC2009) and
the General Service Administration (GSA, 2003) provide methodologies to resist PC of
building Structures and enhance Building robustness.
Structural robustness is defined by the structure’s ability to withstand any unforeseen
loading without a disproportionate response. The study finds that in the absence of the specific
progressive collapse load scenarios and unknown location and extent of initiating damage,
progressive collapse potential can be minimized by employing the concept of structural
robustness as well as safety and reliability, which are all interdependent qualities of a
structural system.
The main objective of this research is to investigate the resistance capacity of several
structural systems under different column removal scenarios. In this study, the linear and
nonlinear static analysis procedures are used. The responses of the structural building systems
are checked in detail and the methodologies to mitigate progressive collapse are discussed.
The study is extended to numerically investigate the effectiveness of these systems by
analyzing a low rise (4 stories) and Med-rise (10-stories) steel building using Alternative Path
Method. For evaluating the potential of progressive collapse, the alternate path method in
[ii]
accordance with both GSA and UFC guidelines is used in two different methods; linear static
analysis and nonlinear static analysis. First, the progressive collapse of the moment resisting
frames is investigated using Alternative Path Method (APM) recommended by GSA and UFC
guidelines.
Generally, the results show that, the low rise steel building structures has no enough
redundancy to redistribute loads of the failed elements so, the potential of progressive collapse
increases with decreasing number of floors and bays of the structure. It was observed that, the
steel moment frames designed for lateral loads as well as gravity load are less vulnerable for
sudden column loss.
The study shows that one of the preferred practices to reduce the potentiality for (PC) is
the use of belt trusses at the top of the building. The use of belt truss system holds the initial
failure of the damaged elements and redistributes the loads supported by the failed elements
with the least increase in the structure’s weight. Moreover, BT can reduce ductility demand.
Different configurations of (BT) as X-bracing, K-Bracing and Eccentric Bracing located at
various levels are investigated. These models are compared in different aspects, such as
economical viewpoint with evaluating the weight of the structure, deflection under lost
column and the energy absorption.
The Nonlinear static procedures is carried out and compared with linear static analysis.
It was observed that, compared with the linear analysis, the nonlinear static analysis provided
larger structural responses and the results varied more significantly depending on the variables
such as applied load, location of removed column, or number of building story. The linear
static step-by-step analysis procedure has advantage in that it is simple and can be conducted
without sophisticated nonlinear modeling. It was observed the cross sections of the redesigned
structural system estimated by linear analysis were higher than those obtained by nonlinear
static analysis. In addition, the maximum vertical deflections estimated by linear analysis
were greater than those obtained by nonlinear static analysis, the linear procedure made more
conservative decision for progressive collapse potential.