Behaviour of Braced and Unbraced Multi-storey Steel Framed Buildings on Flat and Sloping Terrain

Abstract

In recent days, emerging nations have needed new and enhanced infrastructure projects to support their growing populations. There is a daily rise in the demand for residential land as the population expands. In addition to flat land, sloping land in hilly areas must be considered to satisfy the demand for housing land. Moreover, vertical development in the form of multi-storey buildings is the only solution to the problem. In this context the effects of various forms of bracing on the seismic performance of two hill building configurations, such as stepback and stepback-setback, were investigated and compared to a building standing on level ground. A time history dynamic analysis was performed to assess structural responses in terms of seismic parameters such as fundamental time period, top storey lateral displacement, storey drift, base shear, and torsion. The building standing on leveled and sloping ground have been modelled with bracings placed at three different locations, namely at the corners, the mid-edge, and the centre of the building. Buildings standing on sloping land are found to be extremely vulnerable to earthquakes due to irregularities in elevation. X-braced frames, V braced frames, and inverted V braced frames have all been examined in order to identify the best bracing system that significantly improved the seismic resilience of building frames. The Stepback-setback X-braced frame, positioned at the center of the building model, demonstrated the highest percentage decrease in lateral displacement compared to the control model during the El Centro earthquake: 16.27% along and 15.55% across the slope line, respectively. Similar trends were observed for the Northridge and Loma Prieta earthquakes. This highlights the effectiveness of the setback-stepback model with a centrally placed X-bracing system as the preferred choice for buildings on sloping ground due to its superior seismic resilience.