In Chevron BRACED FRAME, due to the buckling of brace on one story, an unbalanced force arrives perpendicularly in the middle of the beam, causing the destroy of the floor and, at the end, causes structural failure. On the lower floor, due to the buckling of the compression member, an unbalanced vertical force has arrived at the location of the upper beam of the braces, which results in a large displacement in the middle of beam. The result is a very strong and uneven beam with other members of the structure. To deal with this situation, Zipper column members are used. In the zipper BRACED FRAME, when the zipper mechanism is formed in the FRAME, the lateral load capacity of the FRAME is reduced and unstable, which can be remedied by applying a suspended BRACED zipper FRAME. In this study, for the comparison of the Chevron BRACED FRAME and Zipper BRACED FRAME from the 4, 7, 10, 15 and 20 stories of the structures under 7 records in the OpenSees software, a analysis dynamic of time history was performed and the maximum parameter required the drift angle of story and the maximum requirement rotation of story for comparison was selected. At the end, it is concluded that the average records in the index of drift angle in the 4 and 7 story FRAME are about 30%, in the 10-story FRAME of about 10%, and in the FRAME 15 and 20 stories less than 5% of the zipper brace FRAME is lower than the chevron BRACED FRAME on the roof. Also, it is deduced from the angles of rotation, Zipper bracing FRAME Average records on the roof is 30% in the 4-story FRAME, 27% in the 7-story FRAME, 8% in the 10-story FRAME, less than 5% in the 15-FRAME FRAME and less than 3% In the 20-story FRAME dropped.

Progressive Collaps is a phenomenon in which a partial damage or local breakdown or initial local failure from one element to another causes a collapse in the whole structure or a large part of the structure. Due to the fact that the behavior of structures in the progressive failure can be related to various factors, such as how the loads are transferred to the nodes, the type of connections and their behavior can be very effective in the progressive Collaps of the structure.Therefore, the study of the effect of the type of connection in the progressive Collaps of the structures can demonstrate the performance of the Resistant systems of the structural steel well. To investigate this issue, steel structures, structures with a number of floors 5, 8, 10, 15 with a folding backrest system whose fittings are tight and fitted with a simple FRAME system whose joints are articulated, loaded and designed based on SAP2000 software. By analyzing the time history of the models, it is determined that the number of seismic responses, including the amount of lateral displacement of the classes, the base cut, the internal force of the columns, and the expansion of the failure in the structures in the use of the bending FRAME and the bracing FRAME relative to Different. It should be noted that the axial, shear and flexural forces of the elements in the FRAMEs are more than the FRAMEs, and based on the position of the column removal, it is different. Therefore, it can be said that the values of internal forces in the bending FRAME are more than the bracing and the amount of vertical displacement and less than the bracing FRAME.

Moment resisting FRAME system and concentric BRACED FRAME system are two systems that are used widely in earthquake resistant buildings. But none of them can respond stiffness and ductility demands simultaneously caused by severe earthquakes. In this study, seismic behavior of knee BRACED FRAME system (as a suggested solution to remove this problem), has been investigated. In this system at least one end of BRACED element, instead of connection to intersection point of beam-column, is connected to inclined knee element that is located between beam and column. BRACED element supplies the stiffness of system, whiles the ductility under severe lateral loads, and is secured by flexural yielding of knee element. The knee element acts as a ductile fuse and prevents buckling of BRACED element. In this research, the behavior of knee BRACED system with different sizes under El Centro earthquake by non-linear Drain-2DX software was examined. This study is done for FRAMEs with 5, 10, 15 and 20 stories. Finally, the effect of building height on the behavior factor is investigated.

In the Eccentric BRACED FRAMEs (EBFs), which one end of the link beam is connected to a column, the safety of the link-to-column connection is a requirement for the ductile and safe performance of the EBF. But among of the tests that have been implemented on this connection yet, because of the intensity of forces on vulnerable region of the link-to-column connection, the tested specimens were confronted with brittle and sudden failures. So it seems that the reduced beam section (RBS) can be a suitable solution for raising this problem, by concentrating flexural stresses at a location away from the connection, in flexural yielding link beams. Therefore in this paper, the possibility of keeping the plastic hinge away from the location of link-to-column connection, in the meanwhile achieving the required plastic rotation of link beam, by using the RBS connection, were investigated. This evaluation was done by using a finite element program ETABS and with nonlinear static analysis (pushover) for a dual system of special moment FRAME and special eccentric BRACED FRAME. According to the present work, the models with RBS by earlier developing the hinge at the RBS region, delay yielding occurrence of link at the column face. So the yielding does not occur at the column face, at least prior to achieving the moment at the location of RBS region to 1.1 times of its expected plastic moment capacity.

Residual displacement after an earthquake disrupts the performance of the structure and leads to local stress. There has been special important in development and the using of self-centering lateral resisting systems that reduces residual drift after a large earthquake. Self-centering lateral resisting systems often include a restoring force component that dissipates seismic energy. Eccentrically BRACED FRAME with vertical link (V-EBF) is one of seismic system based on shear yielding of link beams. If link beam has short length and supplies seismic requirements, link will be able to tolerate significant rotation without strength degradation. Shear link beam has a fat hysteresis curve and height potential of energy dissipation; for this reason the use of short link beam in eccentrically BRACED FRAME was modeled by using experimental models which were provided by other researchers and compared with laboratory results. After validation, 8 and 12 story V-EBF and equipped with SMA rods were designed and their performance were compared with similar structures without SMA rods. In order to compare the structures, pushover, time history and Incremental Dynamic Analysis (IDA) were performed. The results of seismic analysis indicate that the using of SMA rods improves seismic performance and provides excellent reversibility capacity so reduces residual displacement of structure considerably.

BUCKLING-RESTRAINED BRACED FRAMEs can considerably reduce the seismic responses, because of their high energy dissipation capacity. However, they have big residual drifts subjected to great earthquakes. In this paper, BUCKLING-RESTRAINED BRACED FRAMEs with eccentric configurations connected to FRAMEs with post-tension connections is studied. The results show that this system is able to decrease the residual drift. For evaluation the proposed method, 3 and 6 story FRAMEs, for different combinations of self-centering parameters are designed. Self-centering parameters are gradient of disengage connection and ratio of self-centering. Base shear used for the models are calculated using performance-based seismic design. Performance-based seismic design is obtained based on energywork balance using pre-selected target drift and yield mechanism. Then in Abaqus software, pushover and cyclic analysis method for different combinations of self-centering parameters on the FRAMEs is done. Pushover analysis verifies the design method. Cyclic analysis show that the residual drift is decreased by adding FRAMEs with post-tension connections to a buckling –,restrained BRACED FRAME with eccentric configuration. The results show that in order to reach self-centering, the ratio of base shear of the FRAMEs with post-tension connections to the total base shear is required to be more than 50%.

The aim of this study was to investigate the length of the gusset-plate hinge zone proposed by Iranian National Building Code (Part 10) for Special concentrically BRACED FRAMEs (SCBF). For this purpose, numerical studies were done on the seismic behavior of this FRAMEs using ABAQUS software. Numerical modelling procedure is validated using the reproduction of the results of an experimental study. A five story building with Special diagonal concentrically BRACED FRAMEs was modeled in ETABS software and a portal FRAME from the first story of the building was considered for investigation. The detailing of the FRAME was designed for tension and compression based on Iranian code. Seismic behavior of single and double tapered gusset plates with various connection angles and dimensions as well as various length of the hinge zones including-3t,-2t,-t, 0t, t, 2t and 3t were investigated using nonlinear cyclic deformation loading to the ATC-24 test protocol. Seismic behavior of the connections were studied based on ductility, number of cycles before failure, drift before failure and tension and compression strength. Evaluation of the failure limit of the models was carried out using the concept of equivalent plastic strain. Based on the results of the investigated models it can be said that: It is not recommended to use double gusset plates instead of single ones for SCBFs. Gusset plates with a 15 degree angle of inclination have higher ductility capacity and better seismic behavior than ones with a 25 degree angle of inclination. For single gusset plates with a 15 degree angle of inclination, the appropriate length of the hinge zone is-2t, which is not consistent with Iranian code. For single gusset plates with a 25 degree angle of inclination, the appropriate length of the hinge zone is 2t, which is consistent with the Iranian code.

This paper evaluates comprehensively seismic inelastic demand of eccentrically BRACED FRAMEs (EBFs) with vertical members. In this configuration, two zipper-struts are added to connect each end-point of the shear links in all stories. To investigate the efficiency of this system versus conventional EBFs, pushover and incremental dynamic analyses were performed. Results show that in this system, the fully-plastic hinges are almost simultaneously developed in all stories while damage in a conventional EBF concentrates only in a few floors. Moreover, the ductility and energy absorption capacity of this configuration are noticeably higher than those of the conventional EBFs.

Response modification factors (R-factor) are used in current seismic building codes to reduce earthquake forces associated with seismic design level to determine force levels. In recent years, many authors have shown great interest in the development of seismic structural systems and several theoretical and experimental studies have been conducted to investigate performance of dampers, but little attention is given to the response modification factors of steel-BRACED FRAMEs equipped with friction damper. In this study the effect of pall friction damper, as an additional element to the structure, on the parameters of seismic behavior of steel BRACED FRAME is evaluated. Along with the pushover analysis, nonlinear dynamic analysis has been adopted to investigate the components of the behavior factor. For this purpose three steel FRAMEs of 5, 8 and 10 stories were analyzed without considering the existence of dampers, then each FRAME equipped with a friction damper of various slip loads-3, 8, 15, 20, 50 and 100 percentages of weight of the structure- is studied. The results show that behavior factor of chevron BRACED FRAME equipped with friction damper depends on its slip load and changing the R-factor can be an appropriate method to design steel FRAMEs equipped with friction damper.