Effectiveness of various outrigger systems under different structural materials for a reinforced concrete high rise building subjected to wind loads

Abstract

The structural efficiency of tall buildings significantly relies on the lateral stiffness of building and its resistance capacity against lateral loads. However, when the structure becomes taller and slender, the building responses under wind loads become more pivotal as it reduces structural stiffness of building. Therefore outrigger and belt truss structural systems that connect through the central core system and the most exterior columns in building are often introduced in high rise structures to provide adequate lateral stiffness in order to control the wind deflection and drift criteria in acceptable limits. Most research works are limited to building with outrigger systems of concrete material, consisting of simple square and rectangular shaped building plan layouts having vertical regularity. Only few studies were based on a single model under different patterns of outrigger structural systems to identify the optimum outrigger structural system when outrigger arrangements are varied. This study aims to bring a broader understanding of both conventional outrigger & virtual outrigger systems by identifying the most efficient lateral load resisting outrigger system for a reinforced concrete high rise building under different outrigger structural materials of concrete, steel and composite by comparing the performance for three different outrigger arrangements; only outriggers, only belt truss and combination of both outrigger and belt truss when subjected to wind loads while their positions remain constant for all the three cases. The structural performance was evaluated based on building frequency, wind induced lateral displacement at top storey and inter storey drift ratio and results demonstrate that addition of outriggers and belt trusses of different structural materials have significantly enhanced the structural performance of building against wind action and the best form of outrigger structural arrangement is varied based on each structure material.