Analysis of the Structural Collapse of a 26-Story Building

The structural collapse of a 26-story apartment building is analyzed in this paper. The crushing of a concrete column in the first floor caused the collapse of part of the building, comprising 44 apartments from the first to the last floor. Laboratory tests of reinforcement samples and concrete cores extracted from remaining structural elements indicated that the strengths of the materials were in accordance with prescribed design values. In situ inspections revealed signs of faulty construction such as insufficient concrete cover and absence of cross-ties in the columns. The analysis of the structure showed that some columns had a low safety factor and high longitudinal reinforcement ratios, not complying with most codes of practice. The implications of such construction and design errors occurring simultaneously were analyzed in order to identify the most probable cause of the collapse. Questions related to the reasons why a structure under sustained loads could fail after years, in the absence of overloads and foundation settlement, are also addressed in the paper.