OPTIMUM LOCATION OF OUTRIGGERS IN REINFORCED CONCRETE BUILDINGS WITH TUBE IN TUBE SYSTEM USING STAGEDCONSTRUCTION ANALYSIS

Outriggers along with tube-in-tube (TT) systems became a promising alternative to resist wind and earthquakes loadings in addition to controlling excessive drifts in reinforced concrete (RC) high-rise buildings (HRB). Although yielding inaccurate displacements and straining actions, design engineers used to utilize one-step analysis (OSA) instead of staged-construction analysis (SCA) by assuming both all loads are applied at one stage to a complete building. Including time dependent effects in SCA such as shrinkage, creep, and strength gain (SCAT) in the analysis of RC buildings leads to accurate simulation of those structures. In this research, analysis of 140 m and 175 m HRB with TT and outrigger systems is performed using a robust finite element model (FEM) which utilizes SCAT. Optimum locations of one/two outrigger systems are determined by minimizing difference in displacements and straining actions obtained from the OSA and SCAT analyses. Efficiency of the outrigger systems in reducing differences between differential shortenings obtained from OSA and SCAT for the analyzed buildings are assessed. Three locations of one outrigger (1/2 H, 2/3 H, and 1.0 H) and two locations of two outriggers (1/2 H & 1.0 H and 2/3 H & 1.0 H) along the building height (H) are studied as a mitigation technique. Comparing differences between differential displacements and straining actions obtained from SCAT before and after mitigation to their counterparts obtained from SCAT is conducted. The numerical results showed that using two outriggers at 2/3 H & 1.0 H leads to reducing the maximum reduction in differential displacements by 35% and 42% for the two studied buildings. The study revealed that an optimum solution can be achieved by using two outriggers at 1/2 H & 1.0 H. In this case, the differences Optimum Location of Outriggers in Reinforced Concrete Buildings with Tube in Tube System using Staged-Construction Analysis http://www.iaeme.com/IJARET/index.asp 336 editor@iaeme.com between bending moments in horizontal elements before and after mitigation reached 94% for the studied buildings.