Shilpa Nirman Thilakarathna
Design Office Manager
Civil and Structural Engineering Consultants (Pvt.) Ltd, Colombo
Vertical urbanism is an almost inevitable phenomenon with the continued dense, urban development in the modern world. The role of high-rise buildings has therefore evolved from providing only a large office space or residential space in a limited land area to a more advanced, fully functional and self-sustained vertical community. In most cases, the wind loads govern the structural design and the special earthquake demands at potential failure points that could end up being overlooked. Such situations in the past have resulted in major retrofitting works, resulting in not only a cost to the building owners, but also a large expense to the community at large.
In this study, a performance-based seismic analysis of critical elements such as link beams, coupling beams, columns and shear walls of a high-rise building is carried out using Non-linear Response History Analysis (NLRHA). A 45-story twin tower residential building that is being constructed in Colombo, Sri Lanka is used as a case study in this research. Colombo is categorized as a moderate wind zone and a low-to-moderate seismic zone. As a result, the building’s design is governed by wind loads, and the seismic demand estimated through conventional response spectrum analysis is less critical. The results from the non-linear analysis showed that wind-governed design can alter the seismic performance. Carrying out a performance-based seismic evaluation at the design stage will help to identify areas that require additional ductility to satisfy earthquake demands, although the overall design has satisfied critical wind load demands. Such a study will eliminate the risk of future retrofitting work and prevent any undue future expenses.