Assumptions must necessarily be made when the collapse response of structures is investigated using simulation models. The type and extent of modeling assumptions depend on the computational resources available, modeling expertise, and results sought. Modeling choices that are commonly made include planar versus three-dimensional (3D) representation, simplification of member response for modeling purposes, and the use of macroelements to mimic behavior instead of using elements that are based on fundamental constitutive relationships. Using four different types of models, this paper sheds light on the effect of some commonly employed approximations in collapse modeling. The models represent a 10-story seismically designed steel building and encompass computationally expedient planar and 3D macromodels as well as continuum models of individual frames and the full 3D structural system. After a validation exercise, the simulation models are exercised to investigate system collapse response when columns are f...

This study investigates the robustness of a seismically designed steel moment frame building using 3-D nonlinear models. Computational simulations are carried out using validated models to investigate building response to loss of internal and external columns as well as columns in lower, middle and upper floors. Studies are conducted to gain insight into the sources of collapse resistance of the prototype building, focusing in particular on the role of composite action between the slab and underlying steel beams and slab membrane action. The simulation results suggest that the prototype building can be more vulnerable to loss of columns in the upper stories than in the lower ones and is particularly vulnerable to loss of interior gravity columns at all floor levels. The role of the slab is quantified and it is shown that it can contribute significantly to the robustness of the structure, but it is a double edge sword that can also be detrimental, especially in the final stages of collapse.

Relative displacement, which is displacement of a point on a structure with respect to its original location or an adjacent point on the structure that has also undergone movement, can be an effective indicator of postevent structural damage. Although quantifying relative deformations for postevent damage quantification is currently technically feasible, and of great potential benefit, the field remains undeveloped because of lack of knowledge among structural engineers of (1) the enabling technologies and (2) the performance limits of these technologies. The primary objectives of this paper are to review available techniques for measuring relative deformations, identify their limitations, and propose areas where further research is needed. Current methodologies are divided into remote and in situ methods. The latter techniques are deemed most practically feasible and are surveyed in detail and critiqued. Suggestions for current challenges and research opportunities are proposed with emphasis on a...