مقاوم سازی ساختمان های موجود بتنی قاب خمشی بدلیل افزایش تعداد طبقات

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: مقاوم سازی ساختمان های موجود بتنی قاب خمشی بدلیل افزایش تعداد طبقات

ارائه دهنده: Provider: javad ketabi

اساتید راهنما: Supervisors: dr.jalalakbare

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: D.rezaei and D.ketabi

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation:

چکیده: Abstract: Due to the rapid population growth and the increasing need to expand building capacities in urban areas, many existing concrete structures—particularly low-rise buildings—are being subjected to vertical extensions by adding new floors. These modifications can compromise the seismic resistance of the buildings. Therefore, retrofitting such structures against seismic loads, especially in earthquake-prone regions, is of paramount importance. This study focuses on the seismic analysis of three concrete buildings of different heights (3, 7, and 15 stories) designed according to the 3rd edition of the Iranian Seismic Code (Standard No. 2800). The structures were evaluated under various earthquake records, including Tabas, Northridge, and Kobe. As the buildings are vertically expanded by adding additional floors, the necessity for seismic retrofitting becomes particularly critical. Initially, the geometric properties and material specifications of the structures were introduced, and the design of structural elements—including beams, columns, and foundations—was carried out in accordance with established design codes. Selected earthquake records were scaled appropriately to assess the seismic vulnerability of the buildings. Nonlinear dynamic analyses (time history analysis) revealed that the column capacity ratios in the 3-, 7-, and 15-story structures were generally less than 1.0, indicating that the original section designs were adequate. Furthermore, evaluations of inter-story drifts, roof displacements, and base shear demonstrated acceptable structural performance under different seismic events. In the next phase of the study, new floors were added to each structure (2 floors to the 3-story building, 3 floors to the 7-story, and 5 floors to the 15-story structure), and column strengthening was performed using steel jacketing. Subsequent analyses showed that this retrofitting method did not significantly improve the structural performance or column capacities. The results indicated that the selected strengthening sections were inadequate, and the structures remained considerably vulnerable. Finally, by introducing shear walls—a cost-effective and efficient retrofitting method—significant improvements in structural behavior were observed. Inter-story drifts and displacements were reduced below code-specified limits, substantial damage was prevented, and the structures exhibited enhanced resistance to severe earthquakes. Moreover, since all analyses were conducted using SAP2000 software, the accuracy and reliability of the results were significantly improved. This study provides valuable insight for designers and engineers seeking to implement optimal retrofitting strategies for concrete structures subjected to major seismic events. Key Words: Retrofitting, Reinforced Concrete Moment-Resisting Frames, Metal Jacket, Seismic Analysis, Multistory Buildings, Drift, Roof Displacemen