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

Abstract

Summary The outrigger system is an effective tall building system used at one or multiple locations of high‐rise buildings. It is designed to control and minimize lateral displacement and to increase bending stiffness of the buildings by changing the load transfer mechanism of the structural systems. This paper presents a framework for estimation of the optimum location of the outriggers with structural engineering design approach. Three different sample high‐rise buildings, 35‐story 140‐m, 40‐story 160‐m, and 45‐m 180‐m, were investigated. A time‐history analysis method was used to examine the effects of earthquakes. In the first stage, the buildings were assumed to have one outrigger. The outrigger was put on each floor, and ETABS analysis models were created. For each different sample buildings, 35, 40, and 45 different analytical models were utilized for that stage, respectively. In the second stage, in case of outrigger in two positions, all combinations in which outriggers can be located in different positions were taken into consideration for only 40‐story sample building. Considering all of the possible cases, where the steel high‐rise building has 40 floors and the outriggers can be in two different locations, 780 different analysis models were used.

Optimal parameters for tall buildings with a single viscously damped outrigger considering earthquake and wind loads

“…Note that Equation (8) results in a smaller equivalent stiffness than Equation (6), that is, K eq sys < K eq sys . Equations ( 6) and (8) show that as pηχ 1 Ω ! 0,K eq sys !…”

“…Smith and Coull [4] presented an analytical approach for determining the optimum location of one or more outriggers for minimizing the roof drift under a uniform lateral load and provided design curves for the optimum locations in terms of a nondimensional rigidity parameter that includes the flexural rigidities of the core and outriggers and axial rigidity of perimeter columns. Recently several other researchers have investigated the optimum location of single and multiple outriggers using optimization techniques [5–7] and time history analysis [8] and also presented procedures for seismic design of such structures [9] . These studies and the practical application of conventional outriggers [1] have demonstrated the effectiveness of the system in reducing the lateral deflection of tall buildings.…”

Optimal Placement Method of Outrigger With BRB in a Core Wall System Structure

“…Additionally, an inter-story drift parameter analysis for optimal location of outrigger in tall building reported that under earthquake load, the optimal elevation of outrigger is slightly lower compare to that of wind load [8]. Optimum outrigger position using the dynamic time history analysis reported that the optimal location of outriggers depends on the type of earthquake records [9]. They also concluded that it is more effective to locate the single outrigger at the upper part of the tall building to reduce the lateral displacement at the top of the building.…”