A new mitigation scheme to resist the progressive collapse of reinforced concrete buildings

Local failure and damages have led several buildings around the world progressively collapsed during the last few decades. Consequently, several design codes and standards have provoked considering the progressive collapse in designing the buildings according to their occupancy and the potential resulted hazards. In this thesis, a new mitigation scheme is proposed to resist the progressive collapse of reinforced concrete buildings that resulted from potential column failure. The proposed scheme comprises installing steel cables parallel to the columns either externally connected the ends of the beams for retro fitting existing buildings or embedded in the columns for upgrading new buildings. Also, the proposed scheme includes placing a hat braced steel frame on the top of the buildings by which the vertical cables are hanged and supported. When a column failure occurs, the vertical cables will transfer the floor loads upward to the hat braced frame which in turn redistributes these transferred loads to the adjacent columns. A finite element modelling is developed by using the finite element program ANSYS 11.0(2008) and a nonlinear dynamic analysis is conducted following the alternate path method recommended by GSA (2003) and UFC (2009) guidelines to investigate the validity of the proposed scheme. In addition, a simplified technique is developed and programmed in MATLAB 7.8.0 (2009) for designing the vertical cables of the proposed mitigation scheme. Conventional reinforced concrete building models designed according to the Australian Standards AS3600 (2009) have been adopted in the investigations. The analysis results of this study showed the efficiency of the proposed scheme inmitigating the progressive collapse of reinforced concrete buildings. Also, the results show the validity of the developed technique in designing the vertical cables and in predicting the vertical deflection above the failed column.