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Life Cycle Cost-Based Optimal Seismic Design of Steel Buildings with Supplemental Dampers by Utilizing Endurance Time Method

Ahmadie Amiri, Hossein | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 56706 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Esmaeil Pourestekanchi, Homayoon
  7. Abstract:
  8. This study proposes an efficient risk-targeted framework for integrated optimal seismic design and quantifying target safety of steel Special Moment-Resisting Frames (steel SMRFs) with and without various passive damping devices such as Buckling-Restrained Braces (BRBs), Friction Dampers (FDs), and Fluid Viscous Dampers (FVDs). This framework provides an automated design procedure formulated as a constrained single-objective optimization problem to achieve the minimum Life Cycle Cost (LCC) within the Particle Swarm Optimization (PSO) algorithm and can be the basis of current seismic codes for target safety calibration. LCC includes initial construction cost and lifetime seismic losses such as repair cost, repair time, and casualties. FEMA P-58 methodology is employed for the LCC analysis of the building under possible earthquakes during its lifetime, which is able to take into account potential uncertainties in the hazard-response-damage-loss relationship. Appropriate cost models are developed to estimate the initial and repair cost of the studied damping devices. Minimum requirements of ASCE and AISC codes are considered as design constraints. Nonlinear response history analysis through the Endurance Time (ET) method is utilized to estimate the structural responses versus seismic intensity. Three 4-, 8-, and 12-story steel buildings are selected as the case study. Four different seismic force-resisting systems are considered for each building: 1) steel SMRF, 2) steel SMRF with BRB (steel SMRF-BRB), 3) steel SMRF with FD (steel SMRF-FD), and 4) steel SMRF equipped with FVD (steel SMRF-FVD). Each system is optimally designed with two approaches: 1) LCC-based design within the proposed framework and 2) code-based design to minimize initial construction cost. Comparison of optimized buildings with the two design approaches in terms of structural responses and seismic consequences demonstrates that fulfilling the minimum code requirements at a given seismic hazard level is not sufficient to minimize lifetime seismic losses of the studied structural systems. This is because the optimal designs obtained from the code-based approach are associated with damage concentration, irreparability, and high collapse probability, especially in seismic events more severe than the design level. The proposed LCC-based approach provides useful information for improving the lifetime seismic performance of the studied structural systems. The comparison of different structural systems optimized with the LCC-based approach shows that the SMRF system is not a suitable option for achieving limited lifetime seismic losses in long-period building archetypes (8-, and 12-story) located in high-seismicity regions. Therefore, the combination of this well-known system with supplemental damping devices provides a good opportunity to use it in long-period buildings located in high-seismicity regions. In the last section of this study, a more efficient method for utilizing seismic risk analysis in engineering applications is proposed. The proposed method uses the combination of simplified MDOF model and ET analysis method to more efficiently estimate the distribution of Engineering Demand Parameters (EDPs). The efficiency of the proposed method is evaluated using three 3-, 9-, and 20-story SMRFs irregular in bay lengths and three other SMRFs with the same number of stories but irregular in height. In this evaluation, the maximum structural response at all seismic intensity levels up to the collapse stage and also the structural response profile along the building height at SLE, DBE, and MCE seismic intensity levels have been investigated. The efficiency of the proposed method in seismic risk assessment is investigated by using seismic fragility and vulnerability curves. The results of these evaluations have been compared with the full Incremental Dynamic Analysis (full IDA) of the full DOF finite element model of the building under 44 far-field ground motions of FEMA P-695 in terms of computational accuracy and effort. The results show that the proposed method allows the more efficient seismic design of building structures based on LCC by significantly reducing the computational demand and sufficient accuracy in estimating the distribution of EDPs
  9. Keywords:
  10. Optimal Design ; Seismic Design ; Endurance Time Method ; Life Cycle Cost (LCC) ; Simplified Multidegree of Freedom (MDOF) ; Steel Structures ; Buckling Restrained Braces Frame (BRBF)System ; Friction Damper ; Particles Swarm Optimization (PSO) ; Special Moment-Resisting Frames ; Target Safety Quantification ; Viscous Fluid Damper

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