Effects of structural irregularities on the seismic response of a steel structure

Steel structures are commonly used for buildings, bridges, and other infrastructure, due to their high strength-to-weight ratio and versatility. However, the dynamic response of steel structures can be affected by irregularities such as variation in mass, elevation, stiffness, and plan geometry. Therefore, analysis of structural irregularities is important and allows the structural designer to maximize the efficiency of structures in resisting seismic and other dynamic actions. This paper presents a review of the existing methods of analysis of the effects of structural irregularities on the dynamic response of low to medium-high-rise steel buildings. Methods that are used with Eurocode 8 (BS EN 1998:2004) design procedure are discussed. Also, reviewed are the provisions of Eurocode 8, regarding structural irregularity in design, including discussion of the effects of irregularity in mass, elevation, stiffness, and plan. To quantify and compare the effects of different irregularities, SCIA finite element program is used to analyze dynamic response of hypothetical structures with and without irregularities. The computed results of salient deformations and stresses in the structures are compared and discussed, including reference to other researchers' findings. Finally, the implications of various structural irregularities on analysis and design of steel structures are also discussed. The novelty of this research is that it analyses the dynamic response of a predefined structural model, for four types of structural irregularity simultaneously, based on the same control parameters and computational method. Also, even though the use of a building may change at some time, current literature on seismic vulnerability does not adequately address the impact of unexpected changes in mass distribution, but this research does. The findings may help engineers in optimizing design of irregular structures to enhance seismic performance, mitigate risks of seismic damage and promote consistency in design and construction of earthquake resistant structures.