Performance of RC Outrigger and Belt Truss within the Seismic Behavior of Tall Buildings

In tall buildings, usage of efficient structural systems technically and economically is one of the most essential issues. One of these systems can be formed by a central core embedded by framed tubes which contain outriggers and belts truss. This system caused to reduce lateral displacement of structure and moments of the central core. Tall buildings with a central core, belt truss, and outrigger braced system, are usually designed and implemented by steel braces. Now, in this study, RC is replaced instead of steel where coupled shear walls are used within the mentioned system to investigate their performances and behaviors as a new method. The behavior of RC structures with 40, 80 and 120 stories, using outrigger and belt truss system is evaluated. Outriggers and belt truss for efficient performance are located in height of H/2 for 40 story, H/3 and 2H/3 for 80 story and H/4, H/2, 3H/4 for 120 story structures. The simulation results show that the belt truss within the RC structure is the main factor to reduce the roof displacement. It also shows that the effect of belt truss to absorb the shear force is more apparent than the outrigger braced system. In this investigation, drift, maximum roof displacement, absorption percentage of shear force, negative shear force and optimum height for removing central core are evaluated. By adding outriggers and belt truss systems negative shear create in some elevation levels and from this points to the top, core shear wall have negative performance and produce a force in earthquake direction. It is recommended that the optimum height to remove the central core within 40, 80 and 120 story structures is 0.67H, 0.78H, and 0.84H, respectively, where H is the total height of the building.