• Journal of Korean Association for Spatial Structures
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• v.24 no.2
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• pp.75-82
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• 2024

Since atypical high-rise buildings are vulnerable to gravity loads and seismic loads, various structural systems must be applied to ensure the stability of the structure. In this study, the authors selected a 60-story twisted-shaped structure among atypical high-rise structures as an analytical model to investigate its structural behavior concerning the outrigger system. The structural analyses were performed varying the number of installed layers and the arrangement of the outrigger system, as well as the placement of the mega column, as design variables. The analysis revealed that the most effective position for the outrigger was 0.455H from the top layer, consistent with previous studies. Additionally, connecting outriggers and mega columns significantly reduced the displacement response of the model. From an economic standpoint, it is deemed efficient to connect and install outriggers and mega columns at the structure's ends.

• Journal of Korean Association for Spatial Structures
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• v.21 no.1
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• pp.105-112
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• 2021

In this paper, the dynamic response was analyzed by performing linear dynamic analysis using historic earthquake loads on twisted-shaped structures and fixed structure among free-form high-rise structures with atypical elevation shape following prior studies. In addition, the dynamic characteristics of the analysis models according to the plane rotation angle of the twisted structure were compared and analyzed. As a result of the analysis, as the plane rotation angle of the twisted structure increased, the interlayer deformation rate increased in the high-rise part of 50th floors or more. The story shear force and the story absolute acceleration were similar in the entire structure. In the case of the story shear force, the response of the twisted shape model was rather reduced in the middle part. As a result of analyzing the dynamic response, the vulnerable layer where the response amplification of the twisted structure occurs was found to be 31st story.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.17-24
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• 2022

Currently, the construction trend of high-rise structures is changing from a cube-shaped box to a free-form. In the case of free-form structures, it is difficult to predict the behavior of the structure because it induces torsional deformation due to inclined columns and the eccentricity of the structure by the horizontal load. For this reason, it is essential to review the stability by considering the design variables at the design stage. In this paper, the position of the weak vertical member was analyzed by analyzing the behavior of the structure according to the change in the core position of the twisted high-rise structures. In the case of the shear wall, the shear force was found to be high in the order of proximity to the center of gravity of each floor of the structure. In the case of the column, the component force was generated by the axial force of the outermost beam, so the bending moment was concentrated on the inner column with no inclination.

• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.93-100
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• 2020

In this study, structural characteristics were analyzed by combining gravity load and lateral loads such as seismic loads through static analysis of example structures, and the static characteristics of the twisted structure according to the plane rotation angle were also analyzed. Example structures were selected as regular structure, and twisted structures; 1.0, 2.0, and 3.0 degree angle of rotation per story, and static analysis was performed by the load combination case 1 and case 2. As a result the story drift ratio of the twisted-shaped structure also increased as the plane rotation angle per story increased. The eccentricity according to the load combination was the highest in the lower stories of all analysis models, and the eccentricity was found to be larger as the rotation angle decreased. The twisted-shaped structure was more responsible for the bending moment of the column than the regular structure, and the vertical member axial force of all analysis models was almost similar.

• International Journal of High-Rise Buildings
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• v.11 no.4
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• pp.241-263
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• 2022

The conventional wind and twisted-wind effect on aerodynamic properties of neighboring buildings arranged in side-by-side and tandem systems at 2B and 5B spacings are systematically investigated by large eddy simulation. Different physical interactions between different wind profiles and neighboring buildings will be deeply understood. The neighboring-building system under two different types of wind profiles, i.e., conventional wind profile (CWP), twisted wind profiles (TWP) with the maximum twisted angle of 30°, is used to evaluate the variation of physical mechanism between wind and buildings. Aerodynamic characteristics including mean and RMS pressure coefficient, and velocity field were systematically analyzed and compared between different scenario. It was found that the distribution of mean pressure, root-mean-square x velocity and the streamline of wind flow for TWP greatly deviated from CWP, and the effect of TWP on the downstream building, was drastically different from that of CWP, such as the size of vortexes after the lower stream building being bigger when exposed to TWP, and the mean pressure distribution on the building surfaces are also different. Moreover, evidence of buildings arranged in side-by-side and tandem configurations having interchangeable properties under TWP was also discovered, that two buildings being arranged side-by-side exposed to TWP could be identified as being arranged in tandem with a different wind twist angle, or vice versa.

• International Journal of High-Rise Buildings
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• v.5 no.1
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• pp.13-20
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• 2016

Today's architecture can be best understood only through the recognition of pluralism, and, as is true of other building types, multiple design directions are prevalent for tall buildings. This contemporary design trend has produced many complex-shaped tall buildings, such as twisted, tilted and tapered form towers. Among many different structural systems developed for tall buildings, the outrigger system, with its inherent structural efficiency and flexibility in façade design, is widely used for contemporary tall buildings. This paper studies structural performance of outrigger systems employed for complex-shaped tall buildings. Twisted, tilted and tapered tall buildings are designed with outrigger structures, and their structural performance is investigated. For the twisted outrigger study, the buildings are twisted up to 3 degrees per floor. In the tilted outrigger study, the angles of tilting range from 0 to 13 degrees. The impact of eccentricity is investigated for gravity as well as lateral loads in tilted towers. In the study of tapered outrigger structures, the angles of tapering range from 0 to 3 degrees. Parametric structural models are generated using appropriate computer programs for these studies, and the models are exported to structural engineering software for design and analyses.

• International Journal of High-Rise Buildings
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• v.5 no.4
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• pp.243-250
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• 2016

Today's architectural design trend based on the recognition of pluralism has led to multiple design directions for all building types including tall buildings. This contemporary design trend has produced many complex-shaped tall buildings, such as twisted, tilted, tapered and freeform towers. Among many different structural systems developed for tall buildings, the diagrid system, with its powerful structural rationale and distinguished aesthetic potential, is one of the most widely used systems for today's tall buildings. This paper studies structural performance of diagrid systems employed for complex-shaped tall buildings. Twisted, tilted, tapered and freeform tall buildings are designed with diagrid structures, and their structural performances are investigated. For the twisted diagrid study, the buildings are twisted up to 3 degrees per floor. In the tilted diagrid study, the angles of tilting range from 0 to 13 degrees. The impact of eccentricity is investigated for gravity as well as lateral loads in tilted towers. In the study of tapered diagrid structures, the angles of tapering range from 0 to 3 degrees. In the study of freeform diagrid structures, lateral stiffness of freeform diagrids is evaluated depending on the degree of fluctuation of free form. The freeform floor plans fluctuate from plus/minus 1.5 meter to plus/minus 4.5 meter boundaries of the original square floor plan. Parametric structural models are generated using appropriate computer programs and the models are exported to structural engineering software for design, analyses and comparative studies.

• Journal of Korean Association for Spatial Structures
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• v.21 no.4
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• pp.23-30
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• 2021

In this paper, a twisted shape structure with an elevation form favorable to the resistance of vibration caused by wind loads is selected from among the forms of high-rise buildings. The analytical model is a square, triangular, and hexagonal plane with a plane rotation angle of one degree from 0 to 3 degrees per each story. As a result of the analysis, as the twist angle increased, story drift ratio is increased. Responses with different eccentricity rates were shown by analytical models. Therefore planar shapes designed symmetrically to the horizontal axis of X and Y are considered advantageous for eccentricity and torsion deformation. In the case of the bending moment of the column, the response was amplified in the column supporting the base floor, the roof floor, the floor in which the cross-section of the vertical member changes, and the floor having the same number of nodes as the base floor. Finally, the axial force response of the column is determined to be absolutely affected by the gravity load compared to the lateral load.

• International Journal of High-Rise Buildings
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• v.2 no.3
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• pp.229-244
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• 2013

Twenty six pressure models of high rise buildings with various cross-sections including twisted models were tested in a boundary layer wind tunnel. The cross-sections were triangular, square, pentagon, hexagon, octagon, dodecagon, circular, and clover. This study investigates variations in peak pressures, and effects of various cross-sections and twist angles on peak pressures. To study the effects of various configurations and twist angles on peak pressures in detail, maximum positive and minimum negative peak pressures at each measurement point of the building for all wind directions are presented and discussed. The results show that peak pressures greatly depend on building cross-section and twist angle.

• International Journal of High-Rise Buildings
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• v.3 no.3
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• pp.223-230
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• 2014

In this study the progressive collapse resisting capacities of tall diagrid buildings were evaluated based on arbitrary column removal scenario, and the seismic load-resisting capacities were investigated through fragility analysis and ATC 63 procedure. As analysis model structures both regular and twisted diagrid structures were designed and their load-resisting capacities were compared by nonlinear static and dynamic analyses. The analysis results showed that the progressive collapse potential of twisted buildings decreased as the twisting angle increased, but the seismic fragility or the probability of failure decreased as the twisting angle increased.