• Wind and Structures
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• 제3권3호
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• pp.193-207
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• 2000

The possible application of a spatially placed passive tuned liquid column damper system for suppressing coupled lateral-torsional responses of tall buildings is investigated in this paper. The wind loads acting on rectangular tall buildings are analytically expressed as 3-D stochastic model. Meanwhile, the 3-D responses of tall buildings may be coupled due to eccentricities between the stiffness and mass centers of the buildings. In these cases, torsional responses of the buildings are rather larger, and a TLCD system composed of several TLCD located near the sides of the buildings is more effective than the same TLCD placed at the building center in reducing both translational and torsional responses of the buildings. In this paper, extensive analytical and numerical work has been done to present the calculation method and optimize the parameters of such TLCD systems. The numerical examples show that the spatially placed TLCD system can reduce coupled along-wind, across-wind and torsional responses significantly with a fairly small mass ratio.

• Earthquakes and Structures
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• 제2권1호
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• pp.89-107
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• 2011

In this paper a simple mathematical model is presented for estimating the natural frequencies and corresponding mode shapes of a tall building with outrigger-belt truss system. For this purposes an equivalent continuum system is analyzed in which a tall building structure is replaced by an idealized cantilever continuum beam representing the structural characteristics. The equivalent system is comprised of a cantilever shear beam in parallel to a cantilever flexural beam that is constrained by a rotational spring at outrigger-belt truss location. The mathematical modeling and the derivation of the equation of motion are given for the cantilevers with identically paralleled and rotational spring. The equation of motion and the associated boundary conditions are analytically obtained by using Hamilton's variational principle. After obtaining non-trivial solution of the eigensystem, the resulting is used to determine the natural frequencies and associated mode shapes of free vibration analysis. A numerical example for a 40 story tall building has been solved with proposed method and finite element method. The results of the proposed mathematical model have good adaptation with those obtained from finite element analysis. Proposed model is practically suitable for quick evaluations during the preliminary design stages.

• Wind and Structures
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• 제1권1호
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• pp.43-57
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• 1998

A three-degree-of-freedom base hinged assembly (BHA) for aeroelastic model tests of tall building was developed. The integral parts of a BHA, which consists of two perpendicular plane frames and a flexural pivot, enable this modeling technique to independently simulate building translational and torsional degree-of-freedom. A program of wind tunnel aeroelastic model tests of the CAARC standard tall building was conducted with emphasis on the effect of (a) torsional motion, (b) cross-wind/torsional frequency ratio and (c) the presence of an eccentricity between center of mass and center of stiffness on wind-induced response characteristics. The experimental results highlight the significant effect of coupled translational-torsional motion and the effect of eccentricity between center of mass and center of stiffness on the resultant rms acceleration responses in both along-wind and cross-wind directions especially at operating reduced wind velocities close to a critical value of 10. In addition, it was sound that the vortex shedding process remains the main excitation mechanism in cross-wind direction even in case of tall buildings with coupled translational-torsional motion and with eccentricity.

• 한국공간구조학회논문집
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• 제15권3호
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• pp.77-83
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• 2015

The cases of conducting the vibration measurement using the mobile phone with regard to the building's horizontal vibration are very rare in Korea and foreign countries. Therefore, this study analyzed the horizontal vibration nature of the building using the mobile phone targeting 5 tall buildings, and reviewed about the applicability of the mobile phone vibration measuring instrument through the comparison/verification with the data of the existing vibration measuring instrument. The peak of the measured time series waveform was measured clearly and it showed a similar value to the existing natural frequency.

• Structural Engineering and Mechanics
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• 제8권3호
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• pp.243-256
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• 1999

Using appropriate transformations, the differential equation for flexural free vibration of a cantilever bar with variably distributed mass and stiffness is reduced to a Bessel's equation or an ordinary differential equation with constant coefficients by selecting suitable expressions, such as power functions and exponential functions, for the distributions of stiffness and mass. The general solutions for flexural free vibration of one-step bar with variable cross-section are derived and used to obtain the frequency equation of multi-step cantilever bars. The new exact approach is presented which combines the transfer matrix method and closed form solutions of one step bars. Two numerical examples demonstrate that the calculated natural frequencies and mode shapes of a 27-storey building and a television transmission tower are in good agreement with the corresponding experimental data. It is also shown through the numerical examples that the selected expressions are suitable for describing the distributions of stiffness and mass of typical tall buildings and high-rise structures.

• Wind and Structures
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• 제15권6호
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• pp.531-553
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• 2012

Many tall buildings possess through-building gaps at middle levels of the building elevation. Some of these floors are used as sky gardens, or refuge floors, through which wind can flow with limited blockage. It has been reported in the literature that through-building gaps can be effective in reducing across-wind excitation of tall buildings. This paper systematically examines the effectiveness of two configurations of a through-building gap, at the mid-height of a tall building, in reducing the wind-induced dynamic responses of the building. The two configurations differ in the pattern of through-building opening on the gap floor, one with opening through the central portion of the floor and the other with opening on the perimeter of the floor around a central core. Wind forces and moments on the building models were measured with a high-frequency force balance from which dynamic building responses were computed. The results show that both configurations of a through-building gap are effective in reducing the across-wind excitation with the one with opening around the perimeter of the floor being significantly more effective. Wind pressures were measured on the building faces with electronic pressure scanners to help understand the generation of wind excitation loading. The data suggest that the through-building gap reduces the fluctuating across-wind forces through a disturbance of the coherence and phase-alignment of vortex excitation.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.625-648
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• 2015

Modern super-tall buildings are more sensitive to strong winds. The evaluation of wind loads for the design of these buildings is of primary importance. A direct monitoring of wind forces acting on super-tall structures is quite difficult to be realized. Indirect measurements interpreted by inverse techniques are therefore favourable since dynamic response measurements are easier to be carried out. To this end, a Kalman filtering based inverse approach is developed in this study so as to estimate the wind loads on super-tall buildings based on limited structural responses. The optimum solution of Kalman filter gain by solving the Riccati equation is used to update the identification accuracy of external loads. The feasibility of the developed estimation method is investigated through the wind tunnel test of a typical super-tall building by using a Synchronous Multi-Pressure Scanning System. The effects of crucial factors such as the type of wind-induced response, the covariance matrix of noise, errors of structural modal parameters and levels of noise involved in the measurements on the wind load estimations are examined through detailed parametric study. The effects of the number of vibration modes on the identification quality are studied and discussed in detail. The made observations indicate that the proposed inverse approach is an effective tool for predicting the wind loads on super-tall buildings.

• 국제초고층학회논문집
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• 제5권4호
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• pp.293-304
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• 2016

The diagrid structural system for constructing tall buildings is a recent invention. Debuting in 2004 with the construction of the Swiss Re Tower in London, this aesthetically driven structural system has centered the perfecting of its technology on the development of the nodes that form its innovative deviation from standard steel tall framing methods. The paper examines variations in node design, understanding the linked dependence the modularity and the choice to expose the steel in the building, as well as on advances in digital modelling that allow an increasingly seamless line of communication from the engineering design through to the actual fabrication of the nodes. This advanced design and fabrication technology will be seen to have resulted in the expanded use of the technical term "node" to inform the design and construction of a range of other applications in the structuring of tall buildings, including the use of steel castings.

• 국제초고층학회논문집
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• 제8권4호
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• pp.265-273
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• 2019

The purpose of this review paper is to briefly describe main the features of novel procedures developed by the National of Standards and Technology (NIST) for the design of tall buildings. Topics considered in the paper include: the division of tasks between wind and structural engineers; the determination of wind effects with specified mean recurrence intervals by accounting for wind directionality; the risk-consistent design of structures subjected to multiple wind hazards; iterative dynamic analyses and member sizing, including the use of modern optimization approaches; and commonalities of and differences between Database-assisted Design (DAD) and Equivalent Static Wind Loads procedures. An example of the application of the DAD procedure is presented for a reinforced concrete structure. Also included in the paper is an introduction to ongoing research on the estimation of wind load factors or of augmented design mean recurrence intervals commensurate with the uncertainties in the factors that determine the wind effects.

• 한국강구조학회 논문집
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• 제23권2호
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• pp.211-220
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• 2011

다이아그리드 구조시스템은 현재 초고층의 하나의 트렌드로써 미적일뿐 아니라 구조적으로 효율적인 시스템이다. 그러나 이러한 효율적인 다이아그리드가 실제적으로 시공이 어려운 데에는 접합부의 문제가 가장 크다. 접합부는 시공상 어려울 뿐만 아니라, 무엇보다 비용이 많이 들어가기 때문에 실질적으로 다이아그리드 구조를 채택하지 못하고 계획단계에서 그치는 경우가 많다. 본 논문에서는 다이아그리드 노드의 구조적인 물량을 절약하면서 구조적으로 효율적인 다이아 그리드 접합부 모델을 유한요소 해석을 통해서 제안하고 이를 실험에 직접 적용을 시켜 봄으로써 그 효율성을 검증하고자 한다.