Tópicos referentes à influência da consideração do colapso progressivo no dimensionamento e detalhamento dos projetos de edificações

Abstract

Progressive collapse can be defined as the total or partial collapse of a structure resulting from localized damage or failure. Despite its relevance, in view of the consequent economic losses and human lives, this subject is little discussed in Brazilian technical standards, which do not detail methods of structural analysis with the purpose of preventing or mitigating its effects. In this context, the present work seeks to evaluate and compare methods of analysis and prevention of progressive collapse. Therefore, a structural model of a reinforced concrete building is developed, with the help of the TQS® software, in which one of the beams is analyzed from different models, using the conventional methodology for designing beams, based on the equillibrium of forces of the cross-section, and in the equations proposed by Dimas (2014), based on the tension axial force in the beam reinforcement after the loss of the column. The models differ by the use of linear or non-linear static analysis, by the consideration of the original span or the span after the loss of a supporting column, and by the load combination adopted. The evaluation of each model is carried out using the progressive collapse analysis methodology for typical buildings indicated by the General Services Administration (GSA) agency in the United States, based on the Alternative Load Path Method and using the Demand-Capacity Ratio criterion (DCR). For this purpose, Models 1 to 4 are used to design the longitudinal reinforcement of the beam, whose corresponding calculated resistance capacity is compared with the requesting effort obtained from Model 5, which considers the situation after the loss of the column and the load combination indicated by the GSA. The obtained results indicate that the beam disigning by the proposed models is not able to meet the adopted criteria, which means that the methodology presented by the GSA is the most conservative. Then, a final reinforcement detailing for the beam was proposed to meet the verification criteria.