چكيده به لاتين
The seismic load-resisting systems used in buildings these days, provide adequate safety for residents during an earthquake, but these buildings undergo large residual deformations after an earthquake. This can lead to significant repair or reconstruction costs. The concept of self-centering has been introduced to control residual deformation in structures. One way to achieve a self-center system is to use self-center braces. In this research, a new type of self-center braces that has been introduced recently and is based on disc springs and friction plates named as disc spring-based self-centering brace (SBSCB), are investigated and the seismic performance of frames equipped with this type of brace is evaluated. First, the details of the components of the brace and the effective parameters in its performance are examined. Next, two energy dissipation coefficients β and secondary stiffness coefficient γ are defined to describe the behavior of the brace. By specifying these two coefficients as well as the yield strength of the brace, different brace components can be designed. To investigate the effect of these coefficients, 21 braces with different β and γ coefficients are designed and installed diagonally in a single-story single-bay frame. This frame is subjected to quasi-static loading and using the obtained hysteresis for each frame, 3 braces with coefficients β = 1.0 , γ = 1.2 and β = 1.0 , γ = 1.6 and β = 1.0 , γ = 2.0 are selected as braces with maximum energy dissipation capability without leaving residual deformations. In order to study the performance of these three braces in more detail and also to study the effect of the height of the structure, 9 different structures with the number of floors 3, 6 and 9 and equipped with the three braces mentioned above are designed. Also, 3 special concentrically braced frames (SCBF) with 3, 6 and 9 stories are designed to be compared with SBSCB frames. The whole 12 frames are subjected to incremental dynamic analysis and fragility curves are extracted for each. Comparison between these frames shows that the frame equipped with braces designed with coefficients β = 1.0 and γ = 1.2 has the best performance and shows 118% and 504% improvement in collapse capacity and residual deformation control capacity compared to the equivalent SCBF, respectively. Also, the study of the weight of the steel frame of the SBSCB frame and the SCBF shows that in return for the said improvements, the amount of steel consumed in SBSCB frame increases by 17%. The study of the effect of height and fundamental period of the structure in structures with different number of stories and different fundamental periods shows that the rate of improvement in collapse capacity compared to SCBF in 3-story structures with the fundamental period of 0.29 seconds and 6-story structure with the fundamental period of 0.52 seconds are almost. (151% and 152%) but the 9-story structure with a fundamental period of 0.81 seconds (70%) shows less improvement. The highest rate of control of residual deformations is seen in 6-story structures (564% better than the equivalent SCBF) and 3-story and 9-story structures have similar performance in this regard. (384% and 387% better than the equivalent SCBFs, respectively) Thus, it was found that the use of SBSCB frame with design parameters β = 1.0 and γ = 1.2 in a 6-story structure with a fundamental period of 0.52 seconds, in terms of final strength of the structure and control of residual deformations, shows the most improvement relative to the SCBF and is economical in terms of consumable steel and is suitable for use in industry.
