CIVIL ENGINEERING 365 ALL ABOUT CIVIL ENGINEERING



AbstractOver recent years, the application of performance-based design (PBD) has continually grown in the design of tall buildings and other structures excited by large wind loads. PBD has also become a mainstream approach to assess and reduce the risks in the rehabilitation of existing structures. The significant wind-related economic losses incurred every year around the world have prompted researchers to develop methods to reframe wind engineering to embrace the concepts of PBD. The main objective of performance-based wind engineering (PBWE) is to assess the adequacy of a structure in terms of the decision variables (DVs) set forth by the stakeholders. Each DV is defined to satisfy specific performance levels such as operational, immediate occupancy, life safety, and collapse prevention. The performance levels are defined based on acceptable levels of strength and serviceability requirements of both structural and nonstructural components. They also reflect the probable levels of damage, casualties, downtime, and costs of repair. In this paper, a 44-story steel frame building under the action of wind loads was analyzed and evaluated using PBD. To understand the structural response under long-duration wind loads, the building was subjected to randomly varying wind loads for a duration of 30 min. Different time history analyses were conducted with wind speeds varying between 45 and 80  m/s (100 and 180 mph). The basic design wind speed of the building for the preliminary design based on static analysis was 58  m/s (130 mph). The building responses recorded include acceleration and displacement time histories at every floor level. These responses were used to evaluate the peak and root mean squared (RMS) variations of acceleration and interstory drift along the height of the building and also to make comparisons between different wind speeds. The member forces were recorded to identify the locations of plastic hinges and also to interpret any unusual variations in the recorded accelerations and displacements in the building. The fragility and loss ratio curves are presented, showing the response parameters in comparison with the limiting threshold specified by FEMA to categorize the structural components into different damage states (DSs) and corresponding costs of repair or replacement.



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