Seismic Behavior of Virtual Outrigger System

The outrigger system is an economical and effective solution to improve the seismic performance of high-rise buildings. Numerous studies have been carried out on the optimum position of the outrigger system. However, space availability is the main factor as potential locations of outriggers are typically limited to refuge and mechanical floors. This paper proposes some methods to reduce obstructed space at the outrigger level. Comparative studies were performed on A 40-story core-wall building with conventional and proposed virtual outrigger in terms of lateral displacement, drift, base shear, base moment, core moment and fundamental natural period for different positions of the outrigger system. The building was subjected to eleven ground motions scaled to meet the expected peak ground acceleration in Cairo zone. This study concludes recommendations for proposed outrigger configurations which can give higher performance than conventional outrigger and extra free area can be obtained.