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History of past earthquakes and the destruction caused by them show that irregular structures have the vulnerability potential more than other structures. Reinforced concrete (RC) walls are commonly used as the primary lateral-force-resisting system for tall buildings, although for buildings over 49 m (160 ft), IBC 2006 requires use of a dual system. Use of nonlinear response history analysis (NRHA) coupled with peer-review has become a common way to assess the expected performance of tall buildings at various hazard levels to avoid the use of a backup Special Moment Frame for tall buildings employing structural walls. Modeling of the load versus deformation behavior of reinforced concrete walls and coupling beams is essential to accurately predict important response quantities for NRHA. The design of tall buildings essentially involves a conceptual design, approximate analysis, preliminary design and optimization, to safely carry gravity and lateral loads. New developments of tall buildings of ever-growing heights have been continuously taking place worldwide. Consequently, many innovations in structural systems have merged. The design criteria are strength, serviceability, stability and human comfort. The strength is satisfied by limit stresses, while serviceability is satisfied by drift limits in the range of H/500 to H/1000. Stability is satisfied by sufficient factor of safety against buckling and P-Delta effects. The factor of safety is around 1.67 to 1.92. The human comfort aspects are satisfied by accelerations in the range of 10 to 25 milli-g, where g=acceleration due to gravity. The aim of the structural engineer is to arrive at suitable structural schemes, to satisfy these criteria, and assess their structural weights in weight/unit area in square feet or square meters. This initiates structural drawings and specifications to enable construction engineers to proceed with fabrication and erection operations. The weight of steel is often a parameter the architects and construction managers are looking for from the structural engineer. This includes the weights of floor system, girders, braces and columns. The premium for wind is optimized to yield drifts in the range of H/500, where H is the height of the tall building. In this paper, the seismic behavior of steel frames with reinforced concrete core in the duplex and common high rise building are investigated. In this research, linear analysis under 3 kind of earthquake loading (equivalent static, spectral dynamic and dynamic time history) and wind load on structures with 20, 40 and 60 stories have been accomplished and different parameters, such as structure’s base shear and effect of increasing height on seismic behavior have been discussed. Based on results, making structures duplex, causes changes in modal shapes and mass participation percentage of modes. For this reason, there is no change in linear static methods and wind load of common structures and duplex structures response but it has seen changes in structure’s response for 12 far and near earthquake records. In some earthquakes, base shear has been increased maximum 32 percent of common structure’s base shear and also there is no change in base shear in some of them. In some structures, base shear has been decreased maximum 16 percent of common structure’s base shear.
 

Keywords: Tall Buildings, Steel Structure, Duplex, Seismic Behavior, Dynamic Analysis, Wind

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