The steel bracing system is one of the appropriate methods for the strengthening of concrete moment frames against lateral forces. The article purpose is the evaluation of the new strengthening method of reinforced concrete moment frame with convergent bracing and interchangeable link beams that is embedded in the steel frame and installed in the concrete frame spans. This new method is easy to execute, economical and ductile with appropriate performance because of the existence of ductile fuse in its accession section. Therefore, this method is introduced and compared to other strengthening methods by steel bracing. In this article six concrete frame strengthening methods investigated include x-convergent bracing, reverse chevron bracing, divergent bracing with concrete link beam, divergent bracing with steel link beam connected to steel columns in the steel frame, divergent bracing with steel link beam connected to the steel frame with steel columns between those two, divergent bracing with steel link beam connected to the steel frame. All strengthening models attached to concrete frames by a steel frame surrounding them. The linear dynamic analysis results showed a decrease in relative lateral displacement and stress ratio of concrete frame members in all strengthed frames compared to the nonstrengthed frame. Also in the strengthed frame by divergent bracing and steel link beam, the results revealed a 38% steel consumption decrease and an 18% base shear decrease compared to strengthed frame by x-convergent bracing. Nonlinear static and dynamic analysis of models were done by PERFORM-3D software. The nonlinear behavior results of the strengthed concrete frame by divergent bracing with steel link beam connected to the steel frame showed more stiffness, ductility, behavior coefficient and energy dissipation than other models. Also, in this model, an appropriate performance of the structural fuse was shown by the plastic hinge formation of the link beam.

One of the most important determinants of securing the structures in seismic zone is reinforcement of the structures for resisting against the lateral loads. In the recent years, for reinforcing lateral load-resisting systems, implementing applicable elements such as precast concrete and steel plate shear walls as a new approach has attracted many scholars in the area of construction industry. This scholarly attraction refers to the potential benefits of using these advanced operational techniques from the perspective of being affordable, expediting operations and flexibility. Reviewing the research background in the areas of precast concrete frame and steel shear walls reveals that in the past studies, the aforementioned elements have been studied separately and despite the attention of the researchers in the field of civil engineering, none of them have concentrated simultaneously on the systems of precast concrete frame and the steel shear wall together in their studies. Another aspect to consider is the fact that new and modern cities are in the dire need of industrialized construction. This is an important issue since need for quality habitat grows more and more because of high rate of population in the expanding cities. Use of precast segments is a solution in response to this significant demand. Therefore, the present research focuses on the system of precast concrete structures with steel shear walls. In particular, the purpose of this study is to investigate the effect of steel shear wall as a lateral load-resisting element on precast concrete frames using cyclic analysis. In order to achieve the research objectives and performing cyclic analysis, the OpenSEES software was utilized. There are several options in OpenSEES for nonlinear modeling of structural members. They include distributed and concentrated plasticity options. The distributed nonlinearity is closer to reality as experience shows that nonlinear action is actually distributed along a certain portion of members before total failure. On the other hand, use of distributed plasticity option encounters certain difficulties when calculating with reverse loading conditions. The concentrated plasticity option is preferred for the same reason as it has proved to yield results that are close enough to representative response values determined using the other option. That is why the concentrated plasticity computation framework was selected in this research. Moreover, and to the same extent of discussion, different nonlinear stress-strain models can be picked up in OpenSEES. The Steel02 and Concrete02 material constitutive relations benefit from both simplicity and accuracy. The same relations were chosen to cope with the needs of the current research work. For this purpose, the relative behavior of precast concrete frames with a steel shear wall in buildings with different numbers of floors (3, 5 and 10 floors) and different beam-column connections categorized based on their stiffness, strength and construction details as rigid and semi-rigid, were analyzed. Additionally, the behavior of precast concrete frames with steel shear walls (with semi-rigid connections) and concrete frames without steel shear walls (with rigid connection) in buildings having the stated number of floors were examined on the basis of the aforementioned parameters. In general, the results generated by the analysis confirmed the positive and appropriate effect of steel shear walls on the lateral behavior of the precast concrete frame. The results of the research clearly showed that the use of steel shear walls in precast concrete buildings could reinforce lateral load-resisting system and could increase the safety of the structure in the seismic zones. Therefore, this research contributes to the literature by recommending the use of steel shear walls in precast concrete buildings and suggests further studies on this system, including use of a wider range of buildings and earthquake ground motions on various soil types.

The concrete structures exposed to the earthquake have the potential of cracking and reduction in stiffness and strength. Because of their low deformability, there would be some cracking and plastic hinging in the moment-resisting frame. The utilization of dampers is a solution to improve the behavior of the constructed structures. Dampers play a crucial role in improving structural performance level and bearing capacity. In the present study, 9 concrete frames were tested, and steel yield dampers have been used for the seismic rehabilitation of the concrete moment-resisting frames. The yield dampers elements are ADAS dampers (Added Damping and Stiffness) connected to the concrete frame using steel braces. The concentric-type steel braces connect the dampers and concrete beams. Furthermore, to investigate the influence of the braces on the structure’s strength and behavior three concentrated braces have been installed in the structure. The structure in which ADAS dampers was employed demonstrated more strength and less recorded damages than the simple moment-resisting frame. In the present study, the effect of braces and dampers have been investigated in the behavior of the structure, cracking, and strength. The strength of the frames was increased by 48% and 21% by employing steel braces and yield dampers in the concrete frames, respectively, comparing the control frame.

A review of the damages caused by previous earthquakes shows that a significant number of the structures constructed in the country are neither earthquake-resistant nor have enough strength. Consequently, reliable, fast, and easy retrofitting methods are needed to improve these structures to withstand lateral forces. In the present study, 9 concrete frames were tested, and yielding steel dampers have been used for the seismic rehabilitation of the concrete moment-resisting frames. TADAS (Triangular-plate Added Damping and Stiffness) dampers are attached to the concrete frame using steel braces. The dampers and concrete beams are connected with concentric steel braces. Moreover, three concentric braces have been installed to investigate the influence of the braces on the strength and behavior of the structure. Compared to the moment-resisting frame, the structure that used TADAS dampers exhibited greater strength and recorded fewer damages. Cyclic displacement loading was applied to these frames, and their characteristics, including strength and crack, were investigated. In comparison with the control frame, the steel braces and yield dampers increased the structural strength of the concrete frames by 48% and 28%, respectively.

Piezoelectric materials are a type of smart materials that are of interest to many researchers in various engineering sciences due to their extraordinary properties such as converting mechanical energy into electrical energy and vice versa. In this article, the determination and control of the dynamic deformation of a one-span concrete frame with a piezoelectric layer coating on beams and columns under seismic load is discussed. In order to control the dynamic deformation of the concrete frame, a proportional-derivative controller has been used in such a way that a piezoelectric layer is considered as an actuator and a layer as a sensor. The governing equations for the beam and column components of concrete frame are obtained by using high-order shear theory, calculating energy relations, applying Hamilton's principle and considering the applied voltage on piezoelectric materials. In order to solve the dynamic coupled equations, the numerical method of differential quadrature method has been used and finally, with the help of Newmark method, the dynamic deformation of the concrete frame is calculated. After validating the results, the effect of various parameters such as voltage applied to the piezoelectric layer, piezoelectric type controller, thickness of the piezoelectric layer on dynamic deformation were investigated. Here, the optimal values of controller parameters, including proportionality coefficient and derivative coefficient, were obtained as 3.824 and 5.812, respectively. The results show that the use of the controller leads to a reduction of 72 and 65 percent of the lateral and vertical dynamic deflection of the frame, respectively.

There are many concrete infilled frames in Iran, that they need to strengthen . One of the effective methods to strengthen for these buildings, that in recent years many studies have been done about it, is the use of fiber-reinforced composites (FRP). In this paper, we provide a simple method to estimate the stiffness and ultimate load capacity of concrete infilled frame. Infill materials modeled via equivalent diagonal element, are modeled and compared with each other. The two methods can be easily applied to the two-dimensional nonlinear analysis of structures. The result of pushover analysis, offer us a model that is the very close and similar to the prototype. In addition, we provide the results of a case study on a five-story concrete infilled frame with FRP composites have been strengthened, that can be used as a way to replace Infill FRP composites in frames. The laboratory and analytical results that obtained, indicate that the reinforced concrete infilled frame with reinforced FRP composites, increases stiffness and final load capacity of the structure.

History of the earthquakes occurred in Iran indicates that almost every 10 years, a destructive earthquake inflicts damages to the buildings leading to broad life and financial losses. Indeed, seismic retrofit is the process of retrospectively adding elements into the existing buildings in seismically active areas in order to enhance their resistance to the shakings during earthquake events. In doing so, one of the efficient methods is to utilize steel bracing system. To better understand the seismic performance of such systems, in this paper, RC frames retrofitted by CBF and EBF systems were subjected to 7 near-field earthquakes with varying intensities. To this end, two 10-story frames were first designed in compliance with code-based provisions and then, an IDA was conducted on them. The braces are placed in the first and fifth bays of the frame. Based on the results, retrofit of the RC frames by means of concentric and eccentric braces manages to enhance the yield capacity of the frame by 2.3 and 2times, respectively. Moreover, it was found that application of eccentric braces in RC frames, is capable of reducing the base shear by 7times, compared to the frame benefitting from concentric braces. Concerning the impact of this retrofit system on displacement demands, it was observed that when eccentric braces are employed, the roof drifts are less than those of the CBF. Lastly, it was concluded that more flexible behavior of EBF against earthquake records, increases safety and performance level of the structure in Life Safety performance level.

This paper presents an experimental study of steel plate shear wall in the concrete moment frame. This study was based on the idea of using steel plate shear walls in precast concrete structures. The steel plate shear wall was bolted to the embedded plates in concrete boundary elements. These plates were embedded at specified intervals, and friction connection was used for the bolted connections. Semi-static cyclic loading was applied to three different specimens according to ACI T1.1-01 code. Lateral load was applied to the top of specimens. The formation of tension field and buckling waves expressed the required behavior of steel shear walls and, also, good performance of connection scheme. In order to illustrate the effects of adding steel shear plate wall to a concrete frame, one of the specimens was considered to be a bare frame. The results showed the placing of steel shear plate wall in the concrete frame, multiplied loading capacity, initial stiffness, dissipated energy, and equivalent damping of the bare frame by three, eight, twelve, and four, respectively. Horizontal and vertical stiffeners decreased the effects of openings. As diagonal opening with horizontal and vertical stiffeners kept initial stiffness the same and increased dissipated energy and equivalent damping by about 15\%; however, the lateral capacity decreased by 7\%. The results of the strain gauge showed that yielding initiated at a 0.4\% drift level. For the simple steel plate shear wall, the yielding started from corners; for the specimen with openings and stiffeners, it started from the bottom solid panel connected to beam and, also, edges of openings. The stress intensity of the bottom solid panel was more than the rest. Moreover, the steel plate initiated tearing at a drift level of 1.75\%. According to the strain gauge results, embedded corners plates were critical; however, all of them remained elastic. Moreover, it could be said that dissipated energy was obtained from steel plate shear wall. Small bending and shear cracks occurred at the beam-column connection. All of the specimens failed given hinge supports of columns.

One of the most widely used structural systems in existing buildings are reinforced concrete moment resisting frames that offer high ductility and acceptable strength when lateral loads are applied. In the present paper, a laboratory and numerical study of the effect of using non-uniform gap (NSD) dampers in concrete frames has been performed. In the present study, 2 models including a simple frame and a frame with a damper were examined. The reference concrete flexural frame is modeled in a 1: 3 scale, the lengths of beams and columns in the laboratory sample were 1.45 and 1 m, respectively, and the dimensions of beam and column sections were 150 by 150 mm. Reinforcement of the concrete frame was done in such a way as to provide medium torque resistance conditions in the frame. Displacement control loading was used. To study the behavior of the studied samples, force-displacement diagrams of the models were extracted. The results showed that deep cracks were created at the junction of the beam to the column and the structure was damaged. Also, at the junction of the column with the foundation of the structure, it has undergone irreversible deformations and major damage. The study of the effect of NSD damper on deformation and failure showed that the damper can reduce the damage in the concrete frame by absorbing permanent deformation. The results showed that the stresses and deformations of the plastic are concentrated in the damper and the frame performance is almost linear and without damage.