Reliability Analysis of Code-Conforming Steel-Frame Structures against Column-Loss Scenarios

This study investigates the reliability of code-conforming steel-frame structures against column-loss scenarios. The reliability assessment employs the subset simulation method and alternate path method. The subset simulation algorithm is intended to predict the failure probability of the uncertain system. The alternate path method together with a three-dimensional (3D) numerical model is used to evaluate the collapse behavior of sample structures. The developed computational framework is applied to two code-conforming steel-frames structures. The reliability level and most probable failure modes of structures against column loss are obtained. Based on the failure samples generated, sensitivity analyses are carried out. The influential uncertain parameters and their effects are quantified. Finally, the effect of standard tie-force requirements on reducing collapse risk is evaluated. Results show that the failure probabilities of structures with a moment frame missing range from 2.1x10(-3) to 1.9x10(-4) with an average reliability index of 3.05. In contrast, the average failure probability of structure with a gravity column missing is over 0.5. The standard tie-force requirements are found to be insufficient to reduce collapse risk of the structure. The reliability level of the strengthened structure is still 30% lower than the codified target reliability level of 3.0-3.5. (C) 2020 American Society of Civil Engineers.