• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.157-171
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• 2009

A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process of the foundation system of the supertall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes in account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance. The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint. The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.

• Wind and Structures
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• 제13권5호
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• pp.471-485
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• 2010

In comparison with the common two-tower suspension bridge, due to the lack of effective longitudinal restraint of the center tower, the three-tower suspension bridge becomes a structural system with greater flexibility, and more susceptible to the wind action. By taking a three-tower suspension bridge-the Taizhou Bridge over the Yangtze River with two main spans of 1080 m as example, effects of structural parameters including the cable sag to span ratio, the side to main span ratio, the deck's dead load, the deck's bearing system, longitudinal structural form of the center tower and the cable system on the aerodynamic stability of the bridge are investigated numerically by 3D nonlinear aerodynamic stability analysis, the favorable structural system of three-tower suspension bridge with good wind stability is discussed. The results show that good aerodynamic stability can be obtained for three-tower suspension bridge as the cable sag to span ratio is assumed ranging from 1/10 to 1/11, the central buckle are provided between main cables and the deck at midpoint of main spans, the longitudinal bending stiffness of the center tower is strengthened, and the spatial cable system or double cable system is employed.

• Wind and Structures
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• 제24권4호
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• pp.367-384
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• 2017

The Maanshan Bridge over Yangtze River in China is a new long-span suspension bridge with double main spans of $2{\times}1080m$ and a closed streamline cross-section of single box deck. The flutter and buffeting performances were investigated via wind tunnel tests of a full bridge aeroelastic model at a geometric scale of 1:211. The tests were conducted in both smooth wind and simulated boundary layer wind fields. Emphasis is placed on studying the interference effect of adjacent span via installing a wind deflector and a wind separating board to shelter one span of the bridge model from incoming flow. Issues related to effects of mid-tower stiffness and deck supporting conditions are also discussed. The testing results show that flutter critical wind velocities in smooth flow, with a wind deflector, are remarkably lower than those without. In turbulent wind, torsional and vertical standard deviations for the deck responses at midspan in testing cases without wind deflector are generally less than those at the midspan exposed to wind in testing cases with wind deflector, respectively. When double main spans are exposed to turbulent wind, the existence of either span is a mass damper to the other. Furthermore, both effects of mid-tower stiffness and deck supporting conditions at the middle tower on the flutter and buffeting performances of the Maanshan Bridge are unremarkable.

• 대한토목학회논문집
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• 제33권1호
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• pp.219-227
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• 2013

본 연구에서는 연약점토지반에 근입된 송전철탑 기초를 대상으로, 기초부보강공법의 하나인 연결형 기초 형식의 거동과 연결보 특성에 따른 성능발휘 효과를 분석하였다. 이를 위해 유한요소 해석 모델을 구축하였으며, 송전철탑 기초에 연결보의 매트와 닿는 면적비율변화에 의한 거동 및 저항력 특성을 분석하였고, 송전철탑 연결형 기초 모형실험 결과를 이용하여 구축된 유한요소 해석 모델의 타당성의 검증을 실시하여 다양한 매개변수 해석을 통해 연결보의 강성 증가에 따른 효과를 분석하여 송전철탑 연결형 기초의 거동에 효과적인 연결보의 강성을 선정 하였다. 또한, 연결보 자체 휨 모멘트 분포를 확인하여 취약부 분석을 실시하였다.

• 한국지반공학회논문집
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• 제28권8호
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• pp.31-41
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• 2012

연약지반에 건설되는 송전철탑 말뚝기초는 부등침하로 인한 철탑구조체의 손상을 유발 할 수 있다. 이에 따라 일본과 미국에서는 철탑을 지지하는 각 기초부를 연결보로 연결한 연결형기초의 사용을 추천하고 있다(TEPCO 1988, IEEE 2001). 연결형 말뚝기초의 저항력증가계수는 연결체의 영향으로 인하여 증가되는 연결형 말뚝기초의 저항력의 증가량을 나타낸다. 본 연구에서는 점토지반에 근입된 송전철탑 연결형말뚝 기초의 모형수평재하시험을 수행하여 연결형 말뚝기초의 저항력증가계수를 도출하였다. 본 시험은 실트질 점토지반에서 수행되었으며, 수평하중의 재하높이와 재하각도, 말뚝기초를 연결하는 연결체의 강성을 변화시켜 다양한 조건상에서의 저항력 증가계수를 도출하였다. 본 연구에서 도출된 저항력 증가계수는 송전철탑의 하중작용높이와 기초를 연결하는 연결체의 강성에 대한 함수로 나타났으며, 도출된 증가계수를 통하여 연결형 말뚝기초의 저항력을 산정한 결과 측정결과와 비교적 일치하는 것으로 나타났다.

• Smart Structures and Systems
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• 제10권4_5호
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• pp.375-391
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• 2012

This paper reports the structural health monitoring benchmark study results for the Canton Tower using Bayesian methods. In this study, output-only modal identification and finite element model updating are considered using a given set of structural acceleration measurements and the corresponding ambient conditions of 24 hours. In the first stage, the Bayesian spectral density approach is used for output-only modal identification with the acceleration time histories as the excitation to the tower is unknown. The modal parameters and the associated uncertainty can be estimated through Bayesian inference. Uncertainty quantification is important for determination of statistically significant change of the modal parameters and for weighting assignment in the subsequent stage of model updating. In the second stage, a Bayesian model updating approach is utilized to update the finite element model of the tower. The uncertain stiffness parameters can be obtained by minimizing an objective function that is a weighted sum of the square of the differences (residuals) between the identified modal parameters and the corresponding values of the model. The weightings distinguish the contribution of different residuals with different uncertain levels. They are obtained using the Bayesian spectral density approach in the first stage. Again, uncertainty of the stiffness parameters can be quantified with Bayesian inference. Finally, this Bayesian framework is applied to the 24-hour field measurements to investigate the variation of the modal and stiffness parameters under changing ambient conditions. Results show that the Bayesian framework successfully achieves the goal of the first task of this benchmark study.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.687-696
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• 2005

Safety diagnosis was conducted to evaluate the long-term stability evaluation of power transmission tower of which deformation of the upper structural elements occurred. To assess the cause of the structural deformation, field investigation including BIPS, down-hole test, concrete pile coring and finite element analysis were carried out. From these studies, the major cause of deformation was found due to the heavily fractured layer and weathered soil topography at the pile tip area. The cement-milk grouting method was proposed to reinforce these weak zone around the pile tip area. Also, the increase of cross-section and stiffness for steel members of upper tower structures was suggested. Instrumental monitoring was proposed as well to verify reinforcing effect.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.649-661
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• 2007

Friction-type reinforcing members(FRM) to enhance the resistance to wind loads of a transmission tower through both stiffness strengthening and damping increase are energy dissipation devices that utilize bending deflection of a tower leg. In this paper, the hysteretic behavior of the transmission tower structure with FRMs was experimentally investigated through cyclic loading tests on a half scale substructure model. Firstly, the variation of friction forces and durability of the FRM depending on the type of friction-inducing materials used in the FRM were examined by performing the cyclic loading tests on the FRM. Secondly, cyclic loading tests of a half-scale two-dimensional substructure model of a transmission tower with FRMs were conducted. Test results show that the FRM, of which desired maximum friction force is easily regulated by adjusting the amplitude of the torque applied to the bolts, have stable hysteretic behaviors and it is found that there exists the optimum torque depending on a design load by investigating the amount of energy dissipation of the FRMs according to the increase of torque.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.568-577
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• 2007

Friction-type reinforcing members (FRM) to enhance the resistance to wind loads of a transmission tower through both stiffness strengthening and damping increase are energy dissipation devices that utilize bending deflection of a tower leg. In this paper, the hysteretic behavior of the transmission tower structure with FRMs was experimentally investigated through cyclic loading tests on a half scale substructure model. Firstly, the variation of friction forces and durability of the FRM depending on the type of Friction-inducing materials used in the FRM were examined by performing the cyclic loading tests on the FRM. Secondly, Cyclic loading tests of a half-scale two-dimensional substructure model of a transmission tower with FRMs were conducted. Test results show that the FRM, of which desired maximum friction force is easily regulated by adjusting the amplitude of the torque applied to the bolts, have stable hysteretic behaviors and it is found that there exists the optimum torque depending on a design load by investigating the amount of energy dissipation of the FRMs according to the increase of torque.

• 대한조선학회지
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• 제24권2호
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• pp.29-35
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• 1987

As offshore activities move into deeper ocean, conventional fixed-base platforms drastically increase in size and cost, One of alternatives available is a guyed tower, in which environmental loads are supported by guylines instead of structural members. The guying system of the guyed tower is designed on one hand to be stiff enough to limit the structural displacement in normal operations, but on the other hand to be soft enough to permit large slow sways during the presence of design-level storms. This compliancy provides an efficient means of withstanding harsh environment so that the disproportionate increase in size of deep water platforms can be kept to a rational limit. Novel configurations contain always some degrees of potential risks mainly due to the lack of experience. The most critical hazard inherent to a guyed tower may be the pullout of anchor piles. Once it happens, the guyline fails to function and it may eventually lead to the total collapse of the system. It is the aim of this paper to discuss and quantify the anchor-pullout risk of a guyed tower. A stochastic analysis is made for evaluating the first-upcrossing probability of the tension acting on anchor piles over the uplift capacity. Nonlinearities involved in the mooring stiffness and hydrodynamics are taken into account by using time-domain analysis. A simplified two dimensional dynamic model is developed to exemplify the underlying concept. Real hurricane data in the Gulf of Mexico spanning over 70 years are incorporated in a numerical example of which result clearly indicates highly potential risk of anchor pullout.