فهرست مطالب mahshid tavakoli

Buckling restrained braced frames (BRBFs) are widely used as a lateral force resisting system due to their advantageous characteristics such as elimination of brace buckling in compression, high ductility and energy dissipation. BRBFs may have damage concentration in one or few stories during severe seismic excitations, because buckling restrained brace (BRB) yields in a certain story and the stiffness of that story significantly decreases. Drift concentration is undesirable as it can lead to general instability resulting from P-Δ effects or residual drift. For controlling damage concentration in one or few stories and achieving a uniform distribution of drifts in all stories, a new system entitled rocking buckling restrained braced frame (RBRBF) can be used. RBRBF system generates uniform story drifts over the height of structure and prevents the damage concentration in one or few stories. Unlike conventional or suspended zipper braced frames, the braces on one side of the braced span along with the adjacent columns and ties are part of a vertical truss system that is hinged at the base and designed to remain elastic until the near collapse limit state is reached. This vertical truss system works as a strong support for preventing damage concentration in one or few stories of the braced frame. The braces on the other side of the braced span are BRBs and are designed to provide energy dissipation. RBRBFs are designed according to a displacement‐based approach. The novelty of this paper is investigating the residual drift performance of this new structural system under the effect of subduction ground motion records, which have higher significant durations compared with crustal ground motion records. In this study, 4-, 8-, and 12-story structures with RBRBF and BRBF systems are considered, and their residual drift capacity values given four maximum residual interstory drift ratio (MRIDR) levels of 0.2%, 0.5%, 1.0% and 2.0% are computed using incremental dynamic analyses (IDAs). IDAs are performed on two-dimensional models of the structures using 22 pairs of short-duration crustal and long-duration subduction ground motion records. After computing the capacity values given these four MRIDR levels, the residual drift margin ratios (RDMR), and the mean annual frequencies (MAFs) of exceeding different MRIDR levels (λRD) are obtained. The results demonstrate that all the RBRBFs have better residual drift performance than the BRBFs. Based on these results, the use of RBRBF dramatically reduces BRBF weaknesses including the concentration of damage in a certain story and low post-yield stiffness. For example, the ratios of the total λRD value given MRIDR= 2.0% for the BRBF system to its corresponding value for the RBRBF system for the 4-, 8-, and 12-story structures are 21.10, 4.06, and 3.21, respectively. In addition, for most of the structures, as the MRIDR level increases, the ratio of the RDMR value under crustal records to that under subduction records increases.

Buckling Restrained Braces (BRBs) show high ductility and energy dissipation capacity under seismic excitations. It is possible to improve these features by modifying the BRB configuration and the structural system including these braces. Buckling Restrained Braced Frames (BRBFs) may have drift concentration in one story, which leads to the instability of structure due to P-Delta effects and residual drift. To solve the problem of non-uniform damage distribution along the height of structure, which is a disadvantage of BRBFs, researchers have proposed the Rocking Buckling Restrained Braced Frame (RBRBF) system. Each braced bay in this system consists of a conventional brace on one side, a BRB on the other side and a connecting element at the middle of the bay. The conventional brace in one side of the braced bay with the side column and the connecting element form a pin-supported vertical truss system like a rocking wall that behaves elastically until near the collapse of structure. In this study, 4-, 8- and 12-story RBRBFs and BRBFs are considered. Then, by performing non-linear dynamic analyses, the effects of mainshock-aftershock sequences on the seismic collapse of the structures are evaluated, and the results obtained for the two structural systems are compared. The results show that the seismic collapse resistance of each RBRBF under mainshock-aftershock sequences is significantly higher than that of its corresponding BRBF.

Changes in inflammatory mediators have an important role in myocardial infraction. Since the anti-inflammatory effects of Omega-3 fatty acids on cardiovascular diseases was reported, this study was done to evaluate the Omega-3 effect on serum lipid profile, leptin, adiponectin, and E-selectin in patients with myocardial infraction. In this double blinded clinical trial study, 42 patients with myocardial infraction were randomly divided into two mediator and control group. For 10 weeks, the mediator group received 3 capsules of 1 gram Omega-3 daily, and the control group received 3 capsules of placebo (paraffin) daily. Concentration of serum lipid profile, leptin, adiponectin, and E-selectin was measured and compared at the beginning and at the end of the test. IRCT=2021070410181N1 At the end of the study, after comparing the Omega-3 receiving group with placebo group, there was a significant decrease of serum level of triglyceride (120.04±53.24 versus 150.76±48.84, p=0.021), leptin (6.92±2.71 versus 9.05±2.66, p=0.007), and E-selectin (20.98±10.04 versus 6.55±4.12), and there was a significant increase in the serum level of adiponectin (7.24±3.50 versus 6.55±4.12, p=0.026) in patients with myocardial infraction. In both groups, improvement in the size of blood lipids (TC, LDL-C, HDL-C) was obvious when compared to the primary sizes (p<0.05); but the difference between the two complementary and placebo group was not statistically significant. The results show that receiving Omega-3 on a daily basis can modulate inflammatory factors in patients with myocardial infraction.