Outrigger Topology and Behaviour

Abstract

ABSTRACT:The structural efficiency of tall buildings heavily depends on their stiffness and lateral resistance capacity. Among those structural systems for tall buildings, outriggers system is the most common one for buildings with a relatively regular floor plan. Research in outriggers system is relatively limited and usually focuses on the optimal locations/levels of outrigger only. However, the locations of the outriggers are usually dictated by the functional use of the tall buildings and outriggers are usually located in the less commercial valuable floors such as mechanical or refuge floors. Because of this limitation, the topology of outriggers becomes an important element in providing an optimum design. Furthermore, most engineers considered that the performance of buildings is a linear relationship with the stiffness and the critical load of the outriggers. Nevertheless, this is not always true if the ultimate design load condition is being considered. This paper starts with various topologies of outrigger which are commonly used in practice; studies their stability behaviour, compares their stiffness and finally their ultimate load capacity. Examples demonstrate that for some outriggers geometry arrangement or topologies which delivered maximum stiffness and critical loads do not always yield the highest ultimate load capacity even for same outrigger member sizes.

Outrigger and Belt‐Truss System Design for High‐Rise Buildings: A Comprehensive Review Part II—Guideline for Optimum Topology and Size Design

“…ese variables have a direct impact on the provided ductility or stiffness to the structure by the outrigger and belt-truss system. Several reviewed articles studied [9,[32][33][34][35] the optimum value of these variables by applying different methods.…”

“…(xiii) e outrigger geometry arrangement which delivered maximum stiffness does not always yield the highest ultimate load capacity [32].…”

“…(xiv) e diagonal member locations evaluated using topology optimization differ from the assumed member line designed by engineers [33]. (xv) It is recommended to use symmetric truss shape [32]. (xvi) For braced core, up to 25 stories, zipper column core will be more efficient as it provides sufficient lateral stiffness and more space for nonstructural components [16].…”

“…(iii) e relation between the stiffness of the outrigger and the drift is nonlinear [17]. (iv) e diagonal member is more sensitive than the chord member in controlling the drift and displacement [24,26,32,181]. (v) At the high levels, the chord member is more sensitive than the diagonal in controlling the drift [181].…”

Determining the optimum outrigger locations for steel tall buildings by using time history analyses

“…Because of this restriction, the topology of outriggers can be considered an important factor in obtaining an optimal location. [ 2 ]…”