Analysis of outrigger‐braced reinforced concrete supertall buildings: Core‐supported and tube‐in‐tube lateral systems

Abstract

This study is primarily focused on the approximate analysis of reinforced concrete outriggers which are commonly used in the design and construction of supertall buildings subject to distributed horizontal loads. Existing global analysis formulae that provide preliminary results for lateral deflections and moments are reviewed for two lateral load resisting systems, namely, core-supported-with-outrigger (CSOR) system and less frequent tube-in-tube-with-outrigger (TTOR) system. These formulae are only applicable for CSOR and neglect the reverse rotation of the outrigger actually suffered due to the propping action from the outer columns and give rather high predictions of the deflections compared with advanced numerical finite element (FE) models. An improved model is proposed which overcomes this issue and provides more consistent results to FE predictions. The same can also be extended to TTOR.Several case studies are investigated to verify the accuracy of the proposed methodologies. The global analysis is followed by the local analysis of reinforced concrete outrigger beams using strut-and-tie modelling and non-linear FE analysis to obtain optimized reinforcement layouts (reduction of quantities of reinforcement). The results highlight the different challenges in detailing such structural members which are heavily loaded (high congestion of reinforcement), and the behaviour at failure can be brittle.

Simultaneous size and topology optimization of 3D outrigger‐braced tall buildings with inclined belt truss using genetic algorithm

“…The analysis and design of outrigger system for super-tall steel buildings have been investigated by Fang et al [36] considering time-dependent actions such as the differential settlement of the foundation and column shortening; to optimize the construction sequence of the outrigger system, a simple optimum method was proposed based on the overall stiffness and stability of the structure. Nonlinear analysis of RC supertall buildings with outrigger system was carried out by Kafina and Sagaseta [37] to obtain optimized reduced reinforcement.…”