چكيده به لاتين
Evaluation of failure in concrete frames under progressive collapse is a new challenge for engineers Due to the increased magnitude of deformation and the different nature of resistance mechanisms in frame members, and Several studies have been done in recent years to provide effective models for estimating failures and resistances in this field. In this regard, presentation of analytical-based models based on the simplicity of evaluation and the need to simulate and solve numerical equations has been of great importance.
In the present research, analytical methods of progressive collapse assessment have been investigated and the failure prediction process has been searched by these models in variable structural condition. Using a large experimental reference database of valid literature in the technical literature, the responses of two effective and comprehensive analytical models in this field are validated and effective criteria have been investigated on the response process. In developing each analytical method, according to the assumptions and modifications of the model, various structural parameters are interfered that may differ in other cases with other models. However, in the present research, firstly due to the true nature of the mechanisms of resistance and destruction, the variables of effective structural parameters have been identified and then the effect of these parameters on the results of the analytical models has been sought. Finally, by providing these effective parameters on the response of analytic methods , a suitable manner for comparing these methods and adopting a suitable model in different strumental conditions is provided. Also, by performing numerical analysis of concrete frames, the difference in the behavior of the subassemblages under the middle column removal scenario in cases with and without the perimeter frame and effect of vierendeel action has been investigated. This analysis shows that: a) in the frame under progressive collapse, different internal forces develops in the beams above the removed column; b) except for the beams directly connected to the removed column, in the upper beams of the damaged span, the catenary mechanism and in some cases the arc mechanism is not fully developed, and (c) the aggregation of the responses obtained from the analytical methods for the subassemblages with the overall frame response is different.
Keywords: Progressive Collapse, Concrete Frame, Analytical Methods, Resistance Mechanisms, Vierendeel Action.
