Structural reliability of RC frames under sudden column removal scenarios considering static and dynamic methods

2021 ◽  
Author(s):  
Luchuan Ding ◽  
Ruben Van Coile ◽  
Wouter Botte ◽  
Robby Caspeele
Keyword(s):  
Dynamic Analysis ◽  
Structural Reliability ◽  
Progressive Collapse ◽  
Nonlinear Dynamic Analysis ◽  
Load Path ◽  
Dynamic Amplification Factor ◽  
Mean Values ◽  
Column Removal ◽  
Column Removal Scenario ◽  
Failure Probabilities

<p>The alternative load path (ALP) method is widely used to investigate the performance of reinforced concrete (RC) buildings in case of progressive collapse (or disproportional collapse) scenarios. This kind of analysis can be carried out either in a static way or in a dynamic way. In this contribution, these methods are compared by means of nonlinear static and nonlinear dynamic analysis methods. A 5-storey RC frame subjected to two different sudden column removal scenarios is adopted as a case study. The probabilistic analysis considers 12 random variables. On the basis of the stochastic results, a dynamic amplification factor (DAF) is calculated. The mean values of the DAF are 1.114 and 1.102 for the external column removal scenario (Case A) and the internal column removal scenario (Case B), respectively. Compared to the failure probabilities obtained through a static analysis, the failure probabilities for the incremental dynamic analysis results are 184.0% and 180.7% higher for Case A and Case B, respectively.</p>

scholarly journals Progressive collapse scenario in steel structures with irregularity in height

2021 ◽  
Vol 73 (09) ◽  
pp. 893-905
Keyword(s):  
Cross Sections ◽  
Progressive Collapse ◽  
Great Influence ◽  
Nonlinear Dynamic Analysis ◽  
Structural Response ◽  
Steel Structures ◽  
Nonlinear Static Analysis ◽  
Load Path ◽  
Engineering Structures ◽  
Column Removal

Sudden removal of load-bearing elements such as columns in engineering structures, and lack of sufficient capacity to withstand the overload caused by removal of these elements can cause damage and Progressive Collapse (PC) in structures. Therefore, the effect of sudden column removal and structural capacity against PC scenarios in medium and high-rise buildings is investigated in this study. The irregularity in height has a great influence on lateral behaviour of structures and it affects the design of cross-sections. Various sudden column removal scenarios are investigated in this research for steel structures with and without irregularity in height. To assess the effects of sudden column removal, the Alternate load Path Method (APM) and Nonlinear Dynamic Analysis (NDA) are utilized. In addition, a Nonlinear Static Analysis (NSA) is performed to investigate the capacity of structures against the PC phenomenon. Using OpenSees software, 10-, 15- and 20-storey structures with three distinct irregularity types are analysed during four different column removal scenarios. The results are presented in the form of static and dynamic nonlinear curves. The results indicate that making geometric irregularity in height in the sudden column removal scenario can cause the reduction of capacity and growth of the structural response in comparison to the structure with regularity in height. Moreover, the capacity of structures increases and the dynamic response declines by increasing the number of elements in the structures.

scholarly journals Performance Assessment of an Energy–Based Approximation Method for the Dynamic Capacity of RC Frames Subjected to Sudden Column Removal Scenarios

2021 ◽  
Vol 11 (16) ◽  
pp. 7492
Author(s):  
Luchuan Ding ◽  
Ruben Van Coile ◽  
Wouter Botte ◽  
Robby Caspeele
Keyword(s):  
Model Uncertainty ◽  
Probabilistic Models ◽  
Progressive Collapse ◽  
Deformation Mode ◽  
Dynamic Resistance ◽  
Load Path ◽  
Capacity Curve ◽  
Column Removal ◽  
Damping Effects ◽  
Column Removal Scenario

The alternative load path method is widely used to assess the progressive collapse performance of reinforced concrete structures. As an alternative to an accurate non–linear dynamic analysis, an energy–based method (EBM) can also be adopted to approximately calculate the dynamic load–bearing capacity curve or the dynamic resistance based on a static capacity curve. However, dynamic effects cannot be explicitly taken into account in the EBM. The model uncertainty associated with the use of the EBM for evaluating the dynamic ultimate capacity of structural frames has not yet been quantified. Knowledge of this model uncertainty is however necessary when applying EBM as part of reliability calculations, for example, in relation to structural robustness quantification. Hence, this article focuses on the evaluation of the performance of the EBM and the quantification of its model uncertainty in the context of reliability–based assessments of progressive or disproportionate collapse. The influences of damping effects and different column removal scenarios are investigated. As a result, it is found that damping effects have a limited influence on the performance of the EBM. In the case of an external column removal scenario, the performance of the EBM is lower as the response is not a single deformation mode according to the results in the frequency domain. However, a good performance is found in the case of an internal column removal scenario in which the assumption of a single deformation mode is found to be sufficiently adequate. Probabilistic models for the model uncertainties related to the use of the EBM compared to direct dynamic analyses are proposed in relation to both the resistances and the associated displacements. Overall, the EBM shows to be an adequate approximation, resulting in a small bias and small standard deviation for its associated model uncertainty.

scholarly journals Progressive Collapse Assessment: A review of the current energy-based Alternate Load Path (ALP) method

2019 ◽  
Vol 258 ◽  
pp. 02012 ◽  
Author(s):  
Nur Ezzaryn Asnawi Subki ◽  
Hazrina Mansor ◽  
Yazmin Sahol Hamid ◽  
Gerard Parke
Keyword(s):  
Dynamic Analysis ◽  
Static Analysis ◽  
Progressive Collapse ◽  
Structural Response ◽  
Steel Frame ◽  
Collapse Mechanism ◽  
Load Path ◽  
Acceptance Criterion ◽  
Current Energy ◽  
Collapse Assessment

The Alternate Load Path (ALP) is a useful method that has generated a considerable recent research interest for the assessment of progressive collapse. The outcome of the ALP analysis can be assessed either using the force-based approach or the energy-based approach. The Unified Facilities Criteria (UFC- 4- 023-03) of progressive collapse guideline - have outlined that the force-based approach can either be analysed using static or dynamic analysis. The force-based approach using static analysis is preferable as it does not require a high level of skill and experience to operate the software plus no effort is required in scrutinising the validity of the analysis results output. However, utilising the static approach will eliminate the inertial effect in capturing the actual dynamic response of the collapsed structure. In recent years, the development of the energy-based progressive collapse assessment is attracting widespread interest from researchers in the field; as the approach can produce a similar structural response with the force-based dynamic analysis by only using static analysis. Most of the current energy-based progressive collapse assessments are developed following the requirements which are given in the progressive collapse guidelines provided by the Unified Facilities Criteria. However, little attention is given to the development of the energy-based approach using the Eurocode standards as a base guideline. This article highlights the merits of utilising the energy-based approach against the force-based approach for a collapsed structure and explains the collapse mechanism of a steel frame in the perspective of the energy concept. The state of the art of energy-based progressive collapse assessment for a structural steel frame is reviewed. The comprehensive review will include insights on the development of the energy-based method, assumptions, limitations, acceptance criterion and its applicability with the European standards. Finally, potential research gaps are discussed herein.

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