Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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Subject: search.filters.subject.Earthquake resistant design

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  • Doctoral Thesis
    Probabilistic Performance-Based Optimum Seismic Design of Reinforced Concrete Structures
    (01. Izmir Institute of Technology, 2023) Karımzada, Nisar Ahmad; Aktaş, Engin; Girgin, Sadık Can
    Traditional seismic design codes have been developed and used for decades to stipulate the rules for earthquake-resistant design of structures. They are mainly based on the Force-Based Design (FBD) approach and on some linear elastic techniques. The inelastic seismic response of the structure is not directly addressed in the traditional seismic design codes. The initial aim of the current seismic design codes is public safety. In seismic codes, some information is provided regarding the damaged states of structural components, while limited information is provided regarding the damaged states of nonstructural members. In addition, no clear information is provided regarding economic losses and business interruption. The Performance-Based Seismic Design (PBSD) approach, a reliable approach for the seismic design of structures, is capable of providing more detailed information on the performance levels of both structural and nonstructural members and content systems. Some current seismic design codes adapted concepts of the PBSD approach in a deterministic manner, considering uncertainties implicitly. In this study, efforts have been made to develop a Probabilistic Performance-Based Optimum Seismic Design (PPBOSD) methodology for Reinforced Concrete (RC) structures, considering uncertainties explicitly to provide a more practice-oriented approach. It is a powerful seismic design tool that provides structures with economical, robust, and rational design. In addition, structures designed using this approach could satisfy the target performance levels at multi-limit states. For the optimization problem, the objective function is given in terms of minimizing the expected total cost of the structure at a specific intensity level. Pacific Earthquake Engineering Research Center's Performance-Based Earthquake Engineering (PEER PBEE) methodology is used for the performance assessment of the structure. The Endurance Time method is used in the PEER PBEE methodology framework while performing optimization. After the optimum solution is obtained, the Incremental Dynamic Analysis (IDA) method is used to verify the performance levels. The proposed methodology is applied to RC frame buildings with different numbers of stories. OpenSees software is used together with codes written in python for the design and analysis purpose.
  • Doctoral Thesis
    Manipulation of Structural Design Parameters To Mitigate the Concentrarion of Interstory Drift Ratios
    (Izmir Institute of Technology, 2020) Sönmez, Egemen; Dönmez, Cemalettin; Dönmez, Cemalettin
    Although the interstory drift ratio is used as a limiting factor for specific performance levels by the structural engineering profession, its distribution among the stories is generally disregarded. Observations and analytical studies have shown that even the structures are designed to conform seismic design codes, interstory drifts tend to concentrate at certain regions of the frame structures. In other words, the seismic demand the earthquake imposes is attempted to be provided from a limited part of the structure. As a result, the damage concentrates, and the stiffness of the corresponding stories decreases significantly. Locally, the story drifts become larger. Soft-story mechanisms and abrupt failures may occur under such conditions. In this study, a seismic design method was developed to control the distribution of interstory drifts in a frame structure during the nonlinear seismic response. This method is based on two observations: (i) in the inelastic range, the drift distribution is highly dependent on the yield strengths of the members; (ii) there is a strong correlation between the interstory drift distribution and the plastic rotation distribution at member-ends. Thus, an iterative design procedure is developed to control the distribution of the interstory drifts by adjusting the member yield strengths. Plastic rotations are used as a tool for estimating the required yield strengths. The efficiency of the proposed method was tested using nonlinear time-history analyses. The results demonstrated that the frames designed using the proposed method had well-distributed interstory drift and story damage patterns compared to those of the conventionally designed frames. Furthermore, the overall damage of frames was reduced remarkably.