Almost all of seismic design codes for building systems accept heavy damages to buildings, in case of large earthquakes, although they don't accept the building's collapse. Nevertheless, past earthquakes have shown that level of the accepted damage may be so high that demolishing and reconstruction of the building becomes inevitable. This, in turn, results in some unacceptable consequences in large populated cities, such as thousands of homeless and/or jobless people for a very long time, very time consuming, difficult, and costly demolishing and debris removal processes, and finally very massive, and therefore, costly and time consuming required reconstruction works. Regarding these facts, any idea which can lead to creation of repairable buildings is greatly acknowledgeable. One such idea is 'Directed-Damage Design' (DDD) idea, which means guiding the damage to some pre-decided parts of the structural system, so that other parts do not experience any major plastic deformation, and therefore, making the building easily repairable only by replacing the damaged elements. Design of repairable buildings, have been paid great attention by some researchers in recent decade. Use of rocking mechanism of the building's structure (Azuhata et al. 2004) and employing telescopic columns in buildings with rocking/seesaw motion (Hosseini and Noroozinejad Farsangi 2012, Hosseini and Alavi 2014) are some samples of these researches. In previous researches, yielding base plates, yielding bolts, conventional and adaptive viscous dampers, friction dampers and some other devices have been used for energy dissipation. To use the DDD idea for creation of repairable steel buildings with square plan, in this study, a structural system having the capability of seesaw motion with respect to a central massive support has been considered in which the bottom ends of the all circumferential columns at the lowest story have been equipped with Double-ADAS (DADAS) dampers, which dissipate a great portion of the seismic input energy. The hysteretic behavior of DADAS dampers has been investigated by using finite element analysis. Seesaw motion of the structural system can make it possible to concentrate the damages in DADAS dampers at the base level of the building. At first a set of regular steel multistory buildings with 5, 8, 11 and 14 stories have been designed based on the conventional code provisions. Then, the structures of the designed buildings have been changed into the structure with seesaw motion by using, at the base level of the building, a massive central column, eliminating other middle columns, and equipping circumferential columns with DADAS dampers. To show the efficiency of the proposed structural system and dampers, a series of nonlinear time history analysis (NLTHA) have been performed by using a set of 3-component accelerograms of some selected earthquakes. Numerical results of NLTHA show that the proposed seesaw structures can efficiently decrease the seismic damage in the building, so that plastic deformation happens only ...

Passive control methods reduced the vulnerability of structures to earthquakes by decreasing the seismic demand and improving structural plasticity. One of the passive control systems is the eccentrically braced frame with a vertical shear link (V-EBF). The present study aims to direct the damage to the absorbing plates of the vertical link beam to allow the structure’s appropriate seismic performance and reparability. Yielding dampers are one of the most widely used types in systems and can provide perfect vibration control if used optimally. Different types of dampers were introduced and used; how to use them depends on the shape and the way they connect to the structure. This research investigates a new type of damper called box damper, an improved type of shear panel damper. The improvement in the way of connecting to the braced frame and the ease of using this damper in different situations are the features of this new damper. This research investigated the mechanism of these yielding dampers in structures and their strengths and weaknesses. In the next step in this study, a V-EBF with plates of thickness 4, 6, and 8 mm was analysed in the finite element software ABAQUS using the nonlinear static analysis and cyclic loading conditions. Some examples of this damper were attached to the braced frames to investigate the effect of using this damper on the seismic behaviour of the braced structures. The results show that the shear link performs like an electrical fuse absorbing all damage and plastic hinges so that other elements of the braced frame remain in their nonlinear elastic region. By increasing the thickness of the damper from 2 to 8 mm, the resistance increased by two times, and the flexibility of the structure had a noticeable change with the rise in thickness from 2 mm to 8 mm. Ductility increased from 38 to 75 mm.

Purpose The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive strength and elastic modulus under completely dry and wet conditions. Design/methodology/approach In this study, the lightweight concrete made of Light Expanded Clay Aggregate (LECA) as coarse aggregate and sand as fine aggregate was used. To achieve a compressive strength of at least 20 MPa, microsilica was used 10 percent by weight of cement. In order to compensate for the reduction of tension strength of concrete, steel and carbon fibers were used with three volume ratio of 0.5, 1 and 1.5 percent in concrete. The results of concrete specimens were studied at the age of 7, 28, 42 and 90 days under controlled dry and wet conditions. Findings The results showed that the addition of steel and carbon fibers to the concrete mixture would reduce the drop in slump. Also, the use of steel and carbon fibers plays a significant role in increasing the tension strength of the specimens. Furthermore, the highest increase in tension strength of steel and carbon fiber samples was 83.3 and 50 percent, respectively, than the non-fibrous specimen when evaluated at 90 days of age. Moreover, the steel and carbon fiber increased the water absorption of the samples. Adding steel and carbon fibers to a lightweight concretes mixture containing LECA aggregates plays a significant role in increasing the modulus of elasticity of the samples. The highest increase in the elastic modulus of steel and carbon fibers was 18.9 and 35.4 percent, respectively, than the non-fibrous specimen at 28 days of age. Originality/value In this paper, the authors investigated the mechanical properties of steel fiber and carbon reinforced concrete. Also, according to the conditions of storage of samples and the age of concrete (day), the experiments were carried out on samples.

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