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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 48902 (09)
- University: Sharif University of Technology
- Department: Civil Engineering
- Advisor(s): Maleki, Shervin
- Abstract:
- Tension-Only Concentrically Braced Frame (TOCBF) incorporates very slender bracing members, such as single angles, that are unable to dissipate much energy in compression due to their negligible buckling strength. Alternating tension yielding and elastic compression buckling of the bracing elements result in rapid strength degradation during strong motions, which translates into deteriorating pinched hysteresis loops. Based on this unfavorable behavior, it is not recommended to employ TOCBF system for medium and high-rise buildings located in active seismic areas. However, as a result of its inexpensivity and simplicity to design, the TOCBF system is used prevalently in low-rise steel buildings which has not been accompanied by an adequate research effort to understand fully their behavior and rationalize their design.One of the significant issues in utilizing tension-only braces is the determination of appropriate response modification factor (R) for seismic design. This factor accounts for the inelastic deformation during earthquakes, simplifying the design process through a reduction in the seismic force. In order to provide a rational basis for quantifying the seismic performance factors of various structural systems and establishing an acceptable margin of safety against collapse, the FEMA-P695 methodology was developed in 2009. Its approach is used in this study to evaluate the seismic performance factors of TOCBF system. For this purpose, first an assumption is made for the value of R factor that is employed to design and model a set of TOCBF index archetypes in SAP2000. Afterward, the level of safety against collapse provided by the assumed R factor is investigated by the use of nonlinear analysis procedure in the methodology which particularly consists of incremental dynamic analysis under a set of specified ground motions. The results indicated that the optimal seismic design of tension-only braces can be achieved by using an R factor of 3.0 which efficiently provided the intended collapse safety. Also the overstrength factor of the system was derived equal to 2 by performing nonlinear static analysis
- Keywords:
- Incremental Dynamic Analysis ; Response Modification Factor (R) ; Overstrength Column Factor ; Federal Emergency Management Agency (FEMA)P695 Code ; Tension-only Braced Frame ; Collapse Margin Ratio
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