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Optimum Seismic Design Assessment of Tall Buildings Based on Life Cycle Cost Using Endurance Time Method

Sarcheshmehpour, Mohammad | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53590 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Esmail Pourestekanchi, Homayoon; Ghannad, Mohammad Ali
  7. Abstract:
  8. The relatively large number of structural elements and the variety of design code requirements complicate the design process of tall buildings. This process is exacerbated when the target is to obtain the seismic code-compliant optimal design with the minimum weight which results in a large-scale and challenging optimization problem. On the other hand, past earthquakes and hurricanes demonstrated that while satisfying the requirements of the conventional design codes guarantees the life safety of the occupants, significant economic losses may still be incurred. This highlights the importance of considering life cycle costs in the design process of the structures. But the issue is that the optimal design of tall buildings by minimizing their total cost in the lifetime leads to a much larger and more challenging problem than the weight minimization problem. In this research, at first, a practical methodology for the optimal design of tall building structures considering the constraints imposed by typical building codes is proposed. The applicability of the proposed approach is demonstrated through the determination of the optimal seismic design for 20-, 40-, and 60-story buildings with a framed tube as well as a tube-in-tube system. Such a design gives rise to a basis for the fair comparison of the behavior of the framed tube with that of the tube-in-tube system under applied loads. Next, an effective and practical strategy for optimal seismic design of high-rise buildings with the minimum total cost in the lifetime is proposed and employed for investigating the significance of the life cycle seismic risk costs in the design process of steel framed tube tall buildings. In this strategy, the endurance time method is used to perform life cycle cost analysis with a reasonable computational burden. Moreover, by casting the resulting problem into the framework of optimization with the gradient-based algorithms, an efficiently high convergence speed is achieved. Typical 20- and 40-story buildings are optimally designed based on three design approaches: the code-based, the value-based, and the fixed weight approach. The first approach only minimizes the initial cost of the building while in the second and third approaches the total cost of the building in its lifetime is considered. The results indicate that the value-based approach results in the best practical design with the minimum total cost in the lifetime. Furthermore, the code-based design of tall buildings will not necessarily lead to the most economical use of material. However, the minimum base shear requirement specified by the seismic code leads the value-based and the cod-based designs to converge as the height of the building increases
  9. Keywords:
  10. Endurance Time Method ; Structural Optimization ; Seismic Damage ; Value Based Seismic Design ; Life Cycle Cost (LCC) ; Framed Tube Tall Buildings ; High Buildings ; Damage Assessment

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