Dissertation Defence: Seismic Response Factors of Code-designed High-rise Buildings using 3D Non-linear Analysis

Nadeem Hussain, supervised by Dr. Shahria Alam, will defend their dissertation titled “Seismic Response Factors of Code-designed High-rise Buildings using 3D Non-linear Analysis” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.

An abstract for Nadeem Hussain dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Please email shahria.alam@ubc.ca to receive the Zoom link for this defence.

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ABSTRACT

High-rise buildings are important for efficient land use and accommodating growing urban populations. They serve as economic hubs and landmarks, and promote sustainability by reducing sprawl and encouraging lesser disturbance to mother nature. These buildings are often under major threats from natural/manmade hazards like earthquakes, high wind events, fires and explosions, which may cause substantial damage to these structures. This research looks into the seismic response of high rise buildings and their efficient design. In conventional design, the nonlinear behaviour of a structure is accounted for in the elastic analysis-based design method by reducing seismic forces with seismic response modification factors. This plays an important role in the safety and economy of structures. However, these factors cover little information on quality control in providing cost effective structures with a uniform margin of safety. Most seismic provisions were derived using regular building configurations adopting mostly two-dimensional inelastic analysis. This emphasizes on the need for verifying the code recommended seismic design approach for high-rise buildings with various structural systems and irregularities using reliable three-dimensional (3D) assessment methodologies.

Thirteen fibre-based simulation models are designed and developed for buildings ranging from 8 stories to 60 stories covering both steel and R.C. buildings adopting 3D non-linear analysis under medium seismic region. Various structural systems such as moment-resisting frames, bearing walls, and dual systems considering both regular and irregular buildings are designed under the effect of wind and multi-directional earthquake loads. Over 6500 3D inelastic pushover analyses (IPAs) and incremental dynamic analyses (IDAs) using 25 earthquake records are performed to verify the seismic design factors and to derive vulnerability relationships.

The results from the IPAs indicate that the global yield could be estimated through the capacity envelopes using a secant stiffness passing through 70% of the ultimate strength. The effect of building irregularities on the seismic design factors covering various structural systems is provided and a comparative statement is drawn. The relative structural performance and damage states of buildings were also evaluated with higher safety margins using fragility relationships. The performances of buildings with bearing wall systems are compared with the shear wall-frame interactive system. The derived fragility relationships and damage states confirm higher safety margins and results indicate an enhancement in the code recommended story limit of the existing bearing wall structural system.