• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.267-282
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• 2020

The seismic performance and failure modes of the dual system of moment resisting frames and thin steel plate shear walls (TSPSWs) without and with one or two outrigger trusses are studied in this paper. These structural systems were utilized to resist vertical and lateral loads of 40-storey buildings. Detailed Finite element models associated with nonlinear time history analyses were used to examine seismic capacity and plastic mechanism of the buildings. The analyses were performed under increased levels of earthquake intensities. The models with one and two outriggers showed good performance during the maximum considered earthquake (MCE), while the stress of TSPSWs in the model without outrigger reached its ultimate value under this earthquake. The best seismic capacity was in favour of the model with two outriggers, where it is found that increasing the number of outriggers not only gives more reduction in lateral displacement but also reduces stress concentration on thin steel plate shear walls at outrigger floors, which caused the early failure of TSPSWs in model with one outrigger.

• Structural Engineering and Mechanics
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• v.43 no.6
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• pp.711-724
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• 2012

The goal of this study is to conceptually orientate optimized layouts of outrigger belt trusses which are in widespread use today in the design of tall buildings by strut-and-tie truss models utilizing a topology optimization method. In this study unknown strut-and-tie models are realized by using a typical SIMP method of topology optimization methods. In tradition strut-and-tie model designs find the appropriate strut-and-tie trusses along force paths with respect to elastic stress distribution, and then engineers or designers determine the most proper truss models by experience and intuition. It is linked to a trial-and-error procedure based on heuristic strategies. The presented strut-and tie model design by using SIMP provides that belt truss models are automatically and robustly produced by optimal layout information of struts-and-ties conforming to force paths without any trial-and-error. Numerical applications are studied to verify that outrigger belt trusses for tall buildings are optimally chosen by the proposed method for both static and dynamic responses.

• Steel and Composite Structures
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• v.19 no.2
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• pp.263-275
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• 2015

This study presents conceptual information of newly optimized shapes and connectivity of the so-called outrigger truss system for modern tall buildings that resists lateral loads induced by wind and earthquake forces. In practice, the outrigger truss consists of triangular or Vierendeel types to stiffen tall buildings, and the decision of outrigger design has been qualitatively achieved by only engineers' experience and intuition, including information of structural behaviors, although outrigger shapes and the member's connectivity absolutely affect building stiffness, the input of material, construction ability and so on. Therefore the design of outrigger trusses needs to be measured and determined according to scientific proofs like reliable optimal design tools. In this study, at first the shape and connectivity of an outrigger truss system are visually evaluated by using a conceptual design tool of the classical topology optimization method, and then are quantitatively investigated with respect to a structural safety as stiffness, an economical aspect as material quantity, and construction characteristics as the number of member connection. Numerical applications are studied to verify the effectiveness of the proposed design process to generate a new shape and connectivity of the outrigger for both static and dynamic responses.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.303-312
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• 2008

In this paper, the seismic behavior of shear wal-frame systems is analyzed. The governing equations of the wall-frame systems with outrigger truss are formulated through the continuum approach and the whole structure is idealized as a shear-flexural cantileverwith rotational spring. The effect of shear deformation and flexural deformation of the wall-frame and outrigger trusses are considered and incorporated in the formulation of the wall-frame structures with and without outriggers are compared by using finite element analysis incorporated with the Newmark-${\beta}$ method. Numerical results are obtained and compared with the finite element package MIDAS. The proposed method is found to be simple and efficient, and provides reason ably accurate results in the early design stage of tall building structures.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.99-106
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• 2014

This paper presents the determination of the structural system of the Changsha IFC T1 tower with 452 m in architectural height and 440.45 m in structural height. Sensitivity analyses are carried out by varying the location of belt trusses and outriggers. The enhancement of seismic capacity of the outer frame by reasonably adjusting the column size is confirmed based on parametric studies. The results from construction simulation including the non-load effect of structures demonstrate that the deformation of vertical members has little effect on the load-bearing capacity of belt trusses and outriggers. The elastoplastic time-history analysis shows that the overall structure under rare earthquake load remains in an elastic state. The influence of the frame shear ratio and frame overturning moment ratio on the proposed model and equivalent mega column model is investigated. It is found that the frame overturning moment ratio is more applicable for judging the resistance of the outer frame against lateral loads. Comparison is made on the variation of these two effects between a classical frame-core tube-outrigger structure and a structure with diagonal braces between super columns under rare earthquakes. The results indicate that plasticity development of the top core cube of the braced structure may be significantly improved.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.299-309
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• 2014

HSA800 is a new high strength steel (HSS) plate for building structures developed by POSCO and RIST in 2011. It has upper and lower bounds for yield ($F_y$) and tensile ($F_u$) strength as of 650-770MPa and 800-950MPa, respectively, with yield ratio ($F_y/F_u$) limit as of 0.85 which make steel quality more reliable and enhance the seismic resistance of structures. As made by TMCP, it has a good weldability without increasing carbon percentage. The objective of this study is to provide alternative design of mega-structural members of the Lotte World Tower (555m, 123 story), a first super-tall building in Korea, using HSS considering structural safety, constructability, and cost-effectiveness. Steel outrigger trusses, belt-trusses and steel exterior columns were selected and analyzed to evaluate the structural performance between original and alternative designs using HSS. The results show that HSS can be applied to the members which do not affect lateral stiffness of a building and, in this study, approximately 1100tons of steel were saved. It implies that HSS can save overall construction costs - manufacturing, delivery, and erection costs - by reducing mega structural member size. HSA800 was very first applied to the Lotte World Tower based on the results of this study.