Quantification of structural and non-structural robustness of tall steel buildings using a straightforward methodology

Abstract

Assessing the robustness of structures accurately provides structural engineers with important information about constructed or designed buildings. The purpose of this research is to evaluate a straightforward methodology proposed by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) for estimating the robustness index of high-rise buildings with different occupancy. Therefore, 24 and 48-story steel structures with a bundled tube system consisting of nine integrated rigid cells at the height of the building are designed based on AISC 360–16. Six occupancies including Residential, Hotel, Commercial, Parking, Office, and Industries are considered for each group of buildings. The behavior of the structures is investigated using incremental dynamic analysis under near-field earthquakes. Also, the development of seismic performance levels of structures is suggested and the fragility curve of buildings in various limit states was obtained through statistical and probabilistic methods. The damage ratio of the structural system and non-structural components, including mechanical and electrical equipment, exterior walls, and partitions, was determined for each structure type, according to HAZUS guidelines. Then, the suffered direct loss on the buildings was estimated at the risk level with an exceedance probability of 10% over 50 years and a return period of 475 years according to the MCEER report. The studied buildings are considered operational for 30 years and 50 years. Finally, the robustness index and quality function of each part of the buildings is calculated. It is observed that the robustness of the elements of a structure is dependent on the role of its structural or non-structural component in serving the building with a specific occupancy. The results indicate that the height and considered lifespan for the structure have a significant effect in calculating the seismic loss function of tall steel buildings. This methodology can be improved by determining performance measures for buildings with different characteristics and defining new damage factors. It is recommended that to verify the seismic design of structures, an acceptable range for the robustness index can be quantified based on the building characteristics and the specification of the site.