Date of Award

Winter 3-2015

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Department

Civil Engineering

First Advisor

Dr. Aman Mwafy

Second Advisor

Dr. Amr Sweedan

Third Advisor

Prof. Michael N. Fardis

Abstract

Many high-rise buildings are practically irregular as a result of the architectural and service requirements in the design process, errors and modifications during the construction phase, and changes of the building use throughout its service life. Structural irregularities could increase the uncertainties related to the ability of the building to meet the design objectives. This study is thus devoted to assess the safety margins and calibrate the seismic design response factors of modern high-rise buildings with different vertical irregularity features. A brief survey of the most common vertical irregularities in reinforced concrete multi-story buildings is conducted to select reference structures. Five 50-story high-rise buildings are then selected and fully designed using international building codes to represent well-designed tall buildings with principal vertical irregularity types. Fiber-based simulation models are developed to assess the seismic response of the five benchmark buildings under the effect of forty earthquake records representing far-field and near-field seismic scenarios. The comprehensive results obtained from inelastic pushover and incremental dynamic analyses are employed to provide insights into the local and global seismic response of the reference structures. The probabilistic vulnerability assessment of the five high-rise buildings is conducted at different limit states using fragility relationships. The study concluded that the seismic performance of well-designed regular and vertically irregular high-rise buildings is satisfactory under the design earthquake. Under severe earthquakes, the seismic response of tall buildings with extreme soft story and geometric irregularity is not inferior to that of the regular vii counterpart at different seismic performance levels. Despite the overstrength factor adopted in the design of buildings with discontinuities in the lateral-force-resisting system and extreme weak story, the observed negative impacts of these irregularity categories on increasing the vulnerability of high-rise buildings are substantial. This confirms the pressing need for mitigation strategies to reduce the expected seismic losses of the latter classes of building. The calibration of seismic design response factors of the reference high-rise buildings also confirms that, although the code coefficients are adequately conservative, they can be revised to arrive at a more efficient and cost-effective design of regular and irregular high-rise buildings.

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