• Structural Engineering and Mechanics
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• 제34권6호
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• pp.739-753
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• 2010

Pointing to the design requirement of prestressed space grid structure being the target cable force, the pretension scheme decision analysis method is studied when there's great difference between structural actual state and the analytical model. Based on recursive formulation of cable forces, the simulative recursive system for pretension process is established from the systematic viewpoint, including four kinds of parameters, i.e., system initial value (structural initial state), system input value (tensioning control force scheme), system state parameters (influence matrix of cable forces), system output value (pretension accomplishment). The system controllability depends on the system state parameters. Based on cable force observation values, the influence matrix for system state parameters can be calculated, making the system controllable. Next, the pretension scheme decision method based on cable force observation values can be formed on the basis of iterative calculation for recursive system. In this way, the tensioning control force scheme that can meet the design requirement when next cyclic supplemental tension finished is obtained. Engineering example analysis results show that the proposed method in this paper can reduce a lot of cyclic tensioning work and meanwhile the design requirement can be met.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.61-68
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• 2003

In this study, a newly modified soil nailing technology named as the pretension soil nailing system, is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the pretension soil nailing system, has been investigated mainly focusing on an establishment of the design procedure. In the present study, laboratory model tests are carried out to investigate the failure mechanism and behavior characteristics of the pretension soil-nailed wall. Various results of model tests are also analyzed to provide a fundamental basis for the efficient design.

• 대한기계학회논문집A
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• 제27권6호
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• pp.1034-1040
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• 2003

Tension mask is a part of CRT type devices, which is installed right behind glass-made front panel. Numerous slits on the thin metal sheet enable the electron beams emitted from posterior gun to be focused, resulting in enhanced definition. Flattened and enlarged displays necessitate the imposition of pretension on the masks, in order to improve the robustness of display quality against vibration or impact. High temperature assembly process subsequent to pretensioning, however, degenerates creep resistance of mask material, and common mask may become susceptible to undesirable elongation due to creep. Once tensile stress becomes high enough to induce creep deformation, pretension is substantially loosened. In this study, tension mask assembly is modeled as a combined structure of beams and wire array, and a numerical simulation is attempted for pretensioning followed by high temperature process. Based on a model study, creep occurrence is found to be probable and its adverse influence is quantified. As fur maintaining high tensile force, simply increasing pretension does not seem to be helpful. Instead, the structure of frame needs to be modified somehow, or material for mask needs to be selected properly.

• 한국공간구조학회논문집
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• 제17권1호
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• pp.31-40
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• 2017

The objective of this study is to analysis the mechanical characteristics and nonlinear behaviors on the geometric nonlinear behavior of a cable spoke wheel roof system for long span lightweight roof structures. The weight of a cable spoke wheel roof dramatically can reduce and the cable roof system can easily make the required rigidity and shape by the sag ratio and pretension forces. Determining the pretension and initial sag of cable roof system is essential in a design process and the shape of roof is changed by pretension. The nonlinear behavior of flexible cable system has greatly an affect on the sag and pretension. This paper will be carried out analyzing and comparing the tensile forces and deflection of a cable spoke wheel system for the large span retractable roof, and analyzed to deflections and tensile forces by the post height of center hub. The double arrangement of a spoke wheel system with reverse curvature works more effectively as a load bearing system, the pretension can easily increase the structural stiffness. The cable truss system can carry vertical load in up and downward direction, and act effectively as load bearing elements.

• 한국공간구조학회논문집
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• 제16권3호
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• pp.47-58
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• 2016

Cable network system is a flexible lightweight structure which curved cables can transmit only tensile forces. The weight of cable roof dramatically can reduce when the length becomes large. The cable network system is too flexible, most cable systems are stabilized by pretension forces. The tensile force of cable system is greatly influenced by the sag ratio and pretension forces. Determining initial sag ratio of cable roof system is essential in a design process of cable structures. Final sag ratio and pretension depends on initial installed sag and on proper handling during installation. The design shape of cable system has an affect on the sag and pretension, and must be determined using well-defined design philosophy. This paper is carried out the comparative data of the deflection and tensile forces on the geometric non-linear analysis of cable network systems according to sag ratio. The study of cable network system is provided to technical informations for the design of a large span cable roof, analytical results are compared with the results of other researchers. Structural nonlinear analysis of systems having cable elements is relatively complex than other rigid structural systems because displacements are large as a reason of flexibility, initial prestress is applied to cables in order to increase the rigidity, and then divergence of nonlinear analysis occurs rather frequently. Therefore, cable network systems do not exhibit a typical nonlinear behavior, iterative method that can handle geometric nonlinearities are necessary.

• 한국정밀공학회지
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• 제20권6호
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• pp.214-221
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• 2003

Tension mask assembly is positioned right behind the glass-made front panels of CRT type display devices. The frame-supported thin metal sheet contains numerous slits, through which electron beams are focused to enhance definition. Pretension is imposed on the masks, especially for enlarged flat screens, in order to avoid vibration due to acoustic or mechanical impact. High temperature assembly process subsequent to pretensioning, however, degenerates the creep resistance of common mask materials, and if tensile stress is high enough, tension on the mask may be loosened substantially due to creep deformation. In this study, the assembly is modeled as a combined structure of beams and wire array, and a numerical simulation is attempted for pretensioning followed by high temperature process. According to a model study, small amount of creep strain is likely to be generated, but its adverse influence is not negligible. Some structural modification measures to reduce the creep-induced tension loosening are proposed and evaluated. Also, optimal configuration of frame structure is sought for, which maintains high tension of masks and minimizes the possible creep of frame simultaneously.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1401-1402
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• 2013

• 한국지반공학회논문집
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• 제20권7호
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• pp.197-206
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• 2004

쏘일네일링 공법을 도심지 지하굴착 공사에 있어, 지중매설물이 인접하여 존재하거나 대지경계선 등의 준수 등 시공조건에 따라서 설치네일의 길이가 제한되는 경우 및 연약한 지반을 보강할 경우 등과 같은 벽체변위 및 지표침하 억제와 안정성 증대 등을 위하여, 지반앵커공법과 유사한 프리텐션 방식의 도입이 필요한 실정이다. 지반앵커공법과 유사한 프리텐션 방식의 쏘일네일링 공법을 도입하게 될 경우, 단계별 굴착시 발생하는 변위를 최소화할 수 있을 것으로 예상되며 국부적인 안정성도 증대할 것으로 사료된다. 따라서, 본 연구에서는 단계별 굴착시 유발되는 벽체변위 및 침하량 등을 억제하기 위한 노력의 일환으로, 프리텐션 쏘일네일링 시스템을 개발하였다. 또한 최대 프리텐션하중 및 프리텐션 시스템의 안정성을 평가하기 위해, 영향원 반경, 다이레이턴시 각, 정착길이 등을 반영한 설계기법을 제안하였으며, 펀칭전단파괴에 저항할 수 있는 숏크리트의 요구두께를 결정하는 신뢰도 평가기법을 제안하였다. 아울러 설계예제와 $FLAC^{2D}$ 프로그램 수치해석을 통해 프리텐션에 의한 변위 감소효과를 살펴봤으며, 전단강도감소기법을 도입한 안정해석이 $FLAC^{2D}$ 프로그램을 토대로 수행되었다.

• 한국지반공학회논문집
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• 제20권2호
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• pp.87-96
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• 2004

쏘일네일링 공법은 도심지 지하굴착 공사에 있어, 지중매설물이 인접하여 존재하거나 대지경계선 등의 준수 등 시공조건에 따라서 설치네일의 길이가 제한되는 경우 및 연약한 지반조건으로 구성된 사면을 보강할 경우 등과 같은 벽체변위 및 지표침하 억제와 안정성 증대 등을 위하여, 지반앵커공법(ground anchor system)과 유사한 프리텐션 방식의 도입이 필요한 실정이다. 지반앵커공법과 유사한 프리텐션(pretension) 방식의 쏘일네일링 공법을 도입하게 될 경우, 프리텐션 하중에 의해 네일 두부에 부착된 지압판 등은 전면벽체에 수동토압을 유발시키게 되므로, 일반 보일네일링 벽체에서 발생하는 주동토압을 어느 정도 경감시킬 수 있을 것으로 기대되며, 아울러 단계별 굴착시 발생하는 변위를 최소화할 수 있을 것으로 예상된다. 따라서, 본 연구에서는 단계별 굴착시 유발되는 벽체변위 및 침하량 등을 억제하기 위한 노력의 일환으로, 프리텐션 보일네일링 시스템을 개발하였다. 또한 본 연구에서는 실내모형실험을 토대로 프리텐션 쏘일네일링 벽체의 거동특성 및 발휘되는 토압 등을 정량적으로 분석하여 프리텐션 효과에 따른 쏘일네일링 벽체의 파괴유형을 규명하였다. 아울러, 프리텐션 효과가 쏘일네일링 벽체 안정성에 미치는 영향을 검토하여, 향후 예상되는 프리텐션 효과에 따른 수평토압 감소 및 주면마찰력 증가등의 지반-네일 상호작용을 고려한 해석기법개발에 필요한 기초적인 자료를 제시하고자 한다.

• 한국기계가공학회지
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• 제17권1호
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• pp.34-41
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• 2018

A flange joint is a pipe connection used to prevent the leakage of high-pressure fluids by inserting a gasket and tightening the bolts. Among several kinds of gaskets available, metal ring type joint gaskets are most widely used in conditions that require high-temperature and high-pressure fluid flow, such as oil pipelines, gas pipes, pumps, valve joints, etc. The purpose of this study is to investigate the contact pressure and stress characteristics closely related to the sealing performance of Class 900 flange joints used in high temperature and high pressure environments. The dimensions of flange joints with five different nominal pipe sizes were determined with reference to those specified in ASME 16.5. The metal ring gaskets inserted in the joints were octagonal and oval gaskets. The bolt tensile forces calculated from the tightening torques were input as the bolt pretension loads in order to determine the contact pressure and stress levels after fastening. Loading was composed of three steps, including the fastening step, and different amounts of applied pressures were used in each analysis to investigate the effect of fluid pressure on the contact force of the joints. A general-purpose software, ANSYS 17.2, was used for the analysis.