Evaluation of Structural Robustness against Column Loss: Methodology and Application to RC Frame Buildings

Abstract

A computational methodology is presented for evaluating structural robustness against column loss. The methodology is illustrated through application to reinforced concrete (RC) frame buildings, using a reduced-order modeling approach for three-dimensional RC framing systems that includes the floor slabs. Comparisons with high-fidelity finite-element model results are presented to verify the approach. Pushdown analyses of prototype buildings under column loss scenarios are performed using the reduced-order modeling approach, and an energy-based procedure is employed to account for the dynamic effects associated with sudden column loss. Results obtained using the energy-based approach are found to be in good agreement with results from direct dynamic analysis of sudden column loss. A metric for structural robustness is proposed, calculated by normalizing the ultimate capacities of the structural system under sudden column loss by the applicable service-level gravity loading and by evaluating the minimum value of this normalized ultimate capacity over all column removal scenarios. The procedure is applied to two prototype 10-story RC buildings, one employing intermediate moment frames (IMFs) and the other employing special moment frames (SMFs). The SMF building, with its more stringent seismic design and detailing, is found to have greater robustness.

Evaluation of Progressive Collapse Resistance of Steel Moment Frames Designed with Different Connection Details Using Energy-Based Approximate Analysis

“…Expressiveness of all aspects of robustness with clear distinction between robust and non-robust • Objectivity by independence from user decision and reproducibility • Simplicity to gain objectivity, generality, as well as acceptance with users • Ability to calculate the properties and behaviors of the structure with sufficient accuracy and without excessive effort From this viewpoint, structural robustness should be uniquely defined so that it can be quantitatively measured and clearly evaluated with general validity. Bao et al [14] proposed an index r to assess the robustness of a structure. This can be expressed as the ratio of the maximum resistance capacity C to the required capacity D under sudden column loss, as shown in Equation 7, where D can be defined according to an applicable code or standard.…”

“…Failure deformation is applied as 1.15δ u referring to Main and Sadek [26] in order to consider the rapid drop after the ultimate load. The initial stiffness of a spring k bs can be estimated using Equation (14) in the FEMA 355D [28] based on the linear regression of rotational stiffness data from seismic testing.…”

“…Using this analysis, Main and Liu [13] performed column removal scenarios for steel moment frames until the initial failure of the connections to compare the results from the dynamic and energy-based approximate analyses and to evaluate the collapse resistance of the structure. Similarly, Bao et al [14] analyzed the collapse resistance performance for reinforced concrete structures and evaluated the structural robustness as the maximum residual capacity of the structural system that can resist progressive collapse induced by sudden column loss.…”

Fragility and robustness analysis of a multistorey RC building

“…References [68,71,72] and methods described in [73] are used to calculate the structure. In addition, methods presented in [74,80] are used in this paper. The influence of span length on PC of multi-storey buildings is considered in [81], while the influence of irregular structural system on progressive collapse is analysed in [82].…”

A computationally efficient numerical model for progressive collapse analysis of reinforced concrete structures

“…In the worst case, the load-bearing elements can be completely destroyed, which may lead to collapse of the partial or entire structure, a large number of casualties, and marked economical losses. Recent decades have witnessed broad attention from structural engineering community to prevention of structural collapse (Alashker et al, 2011;Bao et al, 2012Bao et al, , 2008Bao et al, , 2017El-Tawil et al, 2013;Iribarren et al, 2011;Kaewkulchai and Williamson, 2004;Khandelwal et al, 2008;Salem et al, 2011;Shi et al, 2010). The definition of the term "progressive collapse" is known as the spread of initial local failure from one or more elements to the neighborhood, which eventually results in the collapse of the entire structure or a disproportionate large part of it (Ellingwood, 2006).…”