جستجوی مقالات مرتبط با کلیدواژه « تغییر شکل پسماند » در نشریات گروه « عمران »

In this research, the effect of P-Delta column (leaning column) on the response of gravitational frames with lateral-load resistance system of base-rocking wall has been investigated. The studied structures have 4-, 8-, 12-, 16-, and 20-stories. Nonlinear dynamic behavior is performed under 22 far-field seismic records and 28 near-field seismic records, half of which are pulse-like, via OpenSees software. The ground motions are scaled at both DBE and MCE levels and applied to the structure. The modeling is done in two dimensions. As a results, it has been shown that 1) the higher modes effect increases with increasing earthquake intensity, 2) the higher modes effect are more visible in the records of far-field and near-field-non pulse-like, 3) residual displacements in The both earthquake levels studied are insignificant and negligible, 4) P-Delta column has been more effective in structures under near-field-pulse-like records, 5) The maximum effect of P-Delta column in increasing the moment of wall under near-field-pulse-like earthquake that the value is 12%, and 6) In general, the effect of the P-Delta column on the base-rocking wall structures in especially the stepping-wall can be ignored.

Nowadays, new and innovative methods have been proposed based on damage avoidance design (DAD) philosophy systems as the alternative conventional lateral load-resistant systems. These systems reduce damage to buildings and post-earthquake reconstruction costs. The self-centering rocking walls are one of them. In this research, multiple rocking wall systems have been investigated and designed. The effect of the number of self-centering blocks and the ratio of tendon prestressing in a 12-story structure examined. The structures have examined subjected to 22 far-field records and 28 near-field records, half of which have pulse. The modeling is done in two dimensions via OpenSees software. The design coefficients of rocking sections in different prestressings for each type of ground motions are specified. The results shown that rocking wall structures under near‐field pulse‐like ground motions need more design capacity than other records to control drift and capacity section. Furthermore, The design of base-rocking and multiple rocking structures has been done for specific drift that have similar drift profiles in height. Then, for this case design, it is not possible to expect the desired energy absorption and also the reduction of the effects of higher modes from the multiple rocking the system compared to the base-rocking system.

Conventional seismic resistant systems generally dissipate earthquake energy through the plastic deformation of structural elements. These systems withstand high residual displacements increasing the cost of repair or even necessitate reconstruction of the building. In recent years, researchers have focused on self-centering lateral load resisting systems due to earthquake energy absorption in replaceable elements and reduced residual displacement. One of the recent types of these systems is self-centering buckling restrained 2-story-X-brace system. In this study, the hysteretic performance of a 9-story structure with a dual steel moment resisting frame system equipped with a self-centering buckling restrained brace is investigated. At first, the parameters affecting the performance of the bracing were specified. These parameters included the yielding stress of the bracing core, the ratio of cable pre-stressing force to the cable yielding force, and the ratio of cable to core area. For the yielding stress of the core two values of 240 and 360 MPa, for the pre-stressing ratio five values from 0.1 to 0.5, and for the area ratio, seven values of 0, 0.25, 0.5, 1, 2.5, 5 and infinity were selected. So therefore, a total of 62 models of 9-story structures with dual steel moment resisting frame system equipped with self-centering buckling restrained brace were constructed. The models were analyzed using OpenSEES finite element software. Performing nonlinear analyses under cyclic loading, the hysteresis diagrams were obtained. The optimal design for these models was performed considering residual displacement and energy absorption as two main parameters. Finally, the performance of the optimized structure equipped with self-centering buckling restrained brace was compared with the structure equipped with ordinary buckling restrained brace. According to the results, the optimized self-centering structure may reduce 60% of the residual displacement while its energy absorption drops by only 37%. Generally, the results indicated the prominence of the optimized self-centering structure.

Bucking restrained braced frame (BRBF) is a special type of concentrically braced frames that the braces do not buckle in compression and as a result shows a desirable energy dissipation behavior. However, low post-yield stiffness of these braces causes large residual deformations at high levels of earthquake itensities. The aim of this article is to evaluate the seismic behavior of a new steel structural system known as hybrid buckling-restrained braced frame (HBRBF). Nonlinear static analysis, nonlinear time history analysis and nonlinear incremental dynamic analysis (IDA) methods are used for standard and hybrid core BRBFs with different stories. The average values of seismic behavior factor (R) for HBRBFs are obtained as 10.2 and 14.7 for ultimate limit state and allowable stress design methods, respectively. In order to carry out response history analyses, past earthquakes records were used with different hazard levels. Hybrid buckling-restrained braced frames are shown to have a significant improvement over standard BRBFs in terms of behavior factor and damage measures including inter-story drift ratios and residual displacements.