Country of Iran due to the existence of numerous faults and stresses by the borders of the shell, has been witnessing the occurrence of many earthquakes throughout the year. Thus providing resistant systems for structural stability against lateral forces of the main concerns of civil engineering in the country. The lateral resistant systems, Eccentrically Brace frame model, which relying on the rotation of LINK BEAM causes the absorption of structural earthquake force, while the excessive rotation of the LINK BEAM region can weaken the structural performance level, and makes some significant cracks in the concrete slab. In the present study, a new model of eccentrically brace system equipped with a steel plate in the lower LINK BEAM, and the BEAM out of the LINKs provided. Numerical modeling in Abaqus software and protocol load is applied based on the ATC-24. The results show that the optimal positioning of steel plates and insert its plates in the lower LINK BEAM and the BEAM out of the LINKs cause improve the shear performance of the bracing system in the development plastic hinges And increased shear strength and ductility of the bracing model. Finally, the energy absorption by the models has a significant performance in comparison with the current model.

Eccentrically braced frames have high stiffness and suitable energy damping against the lateral forces like the earthquake. In this bracing system, the required stiffness and formability of the frame is provided by the LINK BEAM, and are dependent on the details and characteristics of the LINK BEAM. In recent years, Eccentrically Braced Frames (EBF) has been utilized as a resistant system against the earthquake lateral forces. In this paper, using non-linear static analysis, the behavior factors of MRF, CBF, and EBF frames in some models are investigated. These studies are carried on three-storey, six-storey, and ten-storey models, statically linear and non-linear. The results indicate that the EBF behavior factor is largely affected by the LINK BEAM. It is also concluded by the investigating of relative and overall displacements of the mentioned models that these parameters are dependent greatly on the length of the LINK BEAM.

In this paper, a two-LINK flexible manipulator is considered. For a prescribed motion, Timoshenko and EulerBernoulli BEAM models are considered. Using the Galerkin method, nonlinear equations of motion are solved. The Runge-Kutta method is employed for the time response integration method. A comparative study is made between the EulerBernoulli and Timoshenko BEAM models, with and without foreshortening effects. It is demonstrated that for two-LINK manipulators, both theories provide good models, and the results for both theories are very similar for all ranges of slenderness ratio. The findings suggest that for two-LINK manipulators with relatively high slenderness ratios, there is a remarkable difference between the models, considering the foreshortening effect and un-stiffened models. It is obvious that for high precisions applications, the stiffened Timoshenko model is recommended. It is interesting to note that joint torques for the entire range of slenderness ratios are the same.

Passive control methods, by reducing seismic demand and increasing ductility, can reduce magnitude of seismic damage. One of the most effective passive control methods is vertical shear LINK or shear panel system (SPS), in which vertical shear LINK pieces are installed between node of chevron braces and the flange of floor BEAM. In designing this system, the vertical LINK BEAM first yields and dissipates seismic energy, and the remaining elements would stay elastic. Unlike eccentrically braced frames, EBFs, these pieces are not embedded in floor and can be exchanged easily with least effort and less cost after earthquakes. In this paper, five tests were conducted on five specimens of steel braced frames having vertical shear LINKs in different lengths and sections. The results of tests show that the overall performance of these pieces is convincing. In all specimens, shear distortion in vertical shear LINKs varied between 0.128 and 0.156 rad before failure. All specimens had stable hysteretic curves and showed good energy dissipation. Also other structural elements like BEAMs, columns and braces remained elastic. Averages ratios of equivalent viscous damping in specimens varied between 26.7 and 30.6%. In all specimens that had one or more stiffeners (except SPS1 where its weld failed) ductility coefficients reached about 7. Also response modification factors of specimens varied between 7.15 and 10.65 (while 7.15 belonged to SPS1 and response modification factors of other specimens were in range of 8.97 to 10.65 and had more compatibility and less dispersion). Overall, performances of vertical shear LINKs regarding energy dissipation and ductility increase were satisfactory based on experimental results.

In this article, the performance of Eccentrically Braced Frames with Vertical Shear LINKs against progressive collapse has been investigated based on GSA guidelines and the alternative path method. For this purpose, three frames of 5, 10, and 15 floors have been investigated, and their performance was estimated by the method of nonlinear dynamic analysis with SAP2000 software. By removing the middle column for all three frames, it was observed that the displacements are regular and perform well in progressive collapse. However, with the removal of the corner column, the five-story frame collapsed, and for the 10-story frame, an increase of about 3 times the floor displacement was observed. But for the 15-story frame, the behavior of the frame under progressive collapse is very suitable. The removal of the corner column in the frames creates a more critical condition than the removal of the middle column. In the scenario of removing the middle column, the maximum vertical displacement on the last floor of the 5-story frame was equal to 9.21cm, in the 10-story frame it was equal to 6.37cm and in the 15-story frame, it was equal to 4.25cm. For comparison, in the scenario of removing the corner column, the maximum vertical displacement obtained on the last floor of the 5-story frame was unknown due to collapse, and in the 10-story frame it was equal to 21.88cm and in the 15-story frame, it was equal to 7.65cm. Results show that as structure height increases, system behavior will improve against progressive collapse.

Previous studies have demonstrated the occurrence of brittle and early stage cracks in the connection between the LINK BEAM and the column, specifically in the vicinity of the groove welds  that connect  the flanges of the LINK BEAM to the column, when subjected to seismic activity. A similar type of rupture has also been observed in the end-plate connections of the LINK BEAM to the external LINK BEAM. This research explors the consept of utilizing a box-shaped LINK BEAM with a reduced cross-section in the Abaqus finite element software to magnitude the plastic strain demand generated at the flange ends of the box LINK BEAM. The objective is to prevent rupture in this specific region. The results indicate that the maximum equivalent plastic strain at the end of the LINK BEAM flanges can be reduced by up to 38% for short LINK BEAMs, up to 41% for intermediate LINK BEAMs, and up to 68% for long LINK BEAMs. Consequently, this approach effectively prevents premature ruptures in the area adjacent to the groove weld connecting the BEAM flange to the end plate. The magnitude of the equivalent plastic strain at the end of the box LINK BEAM decreases as parameters "a" and "b" decrease, and parameter "c" (geometric parameters of the reduced cross-section) increases. Parameter "c" exhibits the most significant influence on this parameter, while parameter "b" has the least significant impact. Additionally, the adoption of a reduced cross-section in the box LINK BEAM results in an increase of up to 35% in the energy dissipation of the LINK BEAM due to enhanced participation of the flanges in energy dissipation for short LINK BEAMs, up to 158% for intermediate LINK BEAMs, and up to 250% for long LINK BEAMs.

Natural disasters and their harmful impacts have always been one of the most challenging problems all over the world. As such phenomena are inevitable since the distant past mankind has been trying to predict them spatially and temporally and evaluate their loss. Earthquake, as a natural disaster, could not be predicted in time. However, its magnitude and location are predictable to some extent and so is the corresponding loss. Theoretical and computational advances in civil engineering lead to a precise understanding of structures’ behavior and earthquakes. Therefore, in the recent decades, nonlinear behavior and performance-based method have been introduced in the seismic evaluation of structures. Many studies have been carried out in this field by research centers and agencies like FEMA and ATC, resulted in useful guidelines. Eccentrically braced frames have high stiffness and suitable energy damping against the lateral forces like the earthquake. In this bracing system, the required stiffness and formability of the frame is provided by the LINK BEAM, and are dependent on the details and characteristics of the LINK BEAM. In recent years, Eccentrically Braced Frames (EBF) has been utilized as a resistant system against the earthquake lateral forces. The research has shown that the EBF have the ability to combine a high stiffness in the elastic range as well as an excellent ductility and energy dissipation in the inelastic range. Currently, seismic design provisions of most building codes are based on strength or force (base shear) considerations. These building codes are generally regarding the seismic effects as equivalent static forces with a height wise distribution, which is consistent with the first vibration mode shape. However, the design basis is being shifted from strength to deformation in modern performance-based design codes. Determining the shear story and overturning moment under earthquake excitation is an important problem in the seismic design of structures. There are several approaches in order to estimate an acceptable accurate response for the shear story and overturning moment of the structure in the nonlinear region. Both ATC and FEMA approaches are good ideas to evaluate the seismic performance, but more simplified approaches should be applied in seismic design codes. Most of the seismic design codes suggest a very simple relation for estimating the shear story in design base earthquake. In this study, some criterions of the mentioned guidelines are studied, which are about seismic evaluation of the eccentric braced frame (EBF) systems, then the suggestions are offered. In this research, a comparative study has been done to analyze the behavior of regular steel building structures of 4, 8, 12 and 16 stories, located in zones of high seismic hazard and soil type 2. Three-dimensional building systems composed of steel frame system with Intermediate LINK BEAM (EBF) have been selected for investigation. These 3D building structures have been considered with 4, 8, 12 and 16 stories. Then, the performance level of all regular structures is evaluated in one hazard level (with the return period of 475 years). In order to evaluate the performance level of the aforementioned structures, they were modeled three dimensionally using SAP V14. 00 software for both nonlinear static and dynamic analysis. The criteria for predicting the target location guidelines ATC-40, FEMA-356 and modified methods in FEMA-440 were used. The loading pattern design for nonlinear static analysis of single-mode and modal pushover (MPA) was used. For nonlinear time history dynamic analysis out of nine coupled ground motion accelerations from the strong motion database of PEER, with a minimum of 20 km and maximum 45 km from the source and magnitude range of 6 to 7. 5 were selected. The performed procedures in FEMA-356 and proposed plastic hinges in this guideline are utilized for performing the static nonlinear analysis. The soil type II was considered having the shear wave limit between 375 to 750 m/sec. The result and the accuracy of pushover analysis has been compared with the nonlinear time history analysis. This indicates that the results obtained by FEMA-440, are closer to the results of the nonlinear time history dynamic analysis. It is also concluded by the investigating of the shear story and overturning moment of the mentioned models that these parameters are dependent greatly on the length of the LINK BEAM and inadequacy of push-over analysis in demonstrating tall buildings performance are other results of this study.

Based on the literature, experimental investigations on Eccentrically Braced Frames (EBFs), have been limited either to isolated LINK BEAMs under idealized boundary conditions, or subassemblies of the Braced Frames. On the other hand, such tests have also been limited to Wide Flange sections to AISC specifications. In this paper, results of a number of experiments carried out on a single span - single story Eccentrically Brace Frames have been reported. Full scale Braced Frames have been tested in order to investigate the overall behaviour of EBFs, consisting of the LINK BEAM, bracing members and columns, and the effect of connections, bracing members and their interaction to the behaviour of LINK BEAMs have been taken into account. IPE sections to DIN 1025 has been used as LINK BEAMs of the test specimens in order to investigate its competence for use as LINK BEAMs of EBFs; since, these are the only I type sections presently manufactured in the country. At the same time, effects of the distances between the web stiffeners in such shear LINKs as well as the distances between their lateral supports have been investigated. Attention has also been paid to the ductility capacity and the observed modes of failure, with respect to their effects on energy absorption capability of the system due to premature buckling or fracture of the members and connections. The observed behaviour of the test specimens, has been demonstrated clearly and some matters of interest such as the over-strength capacity of the bracing members and the BEAM outside the LINK part, have been discussed with consideration of ductility capacity-demand ratios. It has been shown that the study of an isolated LINK BEAM with idealized boundary conditions, which has been the basis of provisions for the design of EBFs would not represent the compound behaviour of the whole system precisely. While some aspects of the existing seismic design provisions for the EBFs have been assessed, it has been shown that IPE sections may be used as LINK BEAMs of EBFs to achieve the expected performance with the appropriate provision of lateral supports and web stiffeners.