• Journal of the Korean Wood Science and Technology
• /
• v.26 no.3
• /
• pp.9-15
• /
• 1998

The strength and stiffness of structures would be weakened by thermal degradation of wood members which are exposed to a variety of heat including a fire. For this reason, thermal degraded wood members can't pertinently support the load. However, it is easy to repair or rehabilitate wood structures. So, the degraded wood members which can't support the load can be replaced with new members. For the sake of this advantage, there is a need for nondestructive evaluation(NDE) technique, which is very effective to assess wood members in service. In this paper, it was considered whether the stress wave method is adequate to estimate static bending MOE of thermal degraded wood. As the result, the relationship between static bending MOE and MOEsw in elevated temperature was found out significant. Therefore, the application of stress wave method for estimating static bending MOE of thermal degraded zzwood would be possible. However, it is thought that further research for the effects of exposure temperature, time, and thermal degradation on the relationship between static bending MOEb and MOEsw would be needed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.357-360
• /
• 2008

This study was performed to estimate the workability and the static behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Static test was executed for 20m railway bridge girder specimen and evaluated whether pure bending moment was introduced or not, and the behaviors after cracking, and at the ultimate load. Test results showed that a bicon girder had the enough safety in the introduction of pure moment, the serviceability, and the ultimate behavior.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.361-364
• /
• 2008

This study was performed to estimate the anchorage behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Therefore, the steel bar and the steel tendon must be unified in both ends and compressive and tensile force be offset. Anchorage dimension of 6 test specimens was designed under PTI specification which defined maximum stress and deformation to estimate structural behavior. Test results showed that the stress and the deformation of anchorage were within limits if the steel bar behaviored elastically.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.11 no.2
• /
• pp.15-26
• /
• 1991

The lateral forces such as the earthquake and wind my cause the torsion to be coupled with the lateral bending in the gider, the cross-section of wich has only one axis of symmetry. This induces additional stresses especially in cables arranged in double-planes. Since this effect cannot be considered by using the conventional frame elements, the stiffness and the mass matrices of the geometrically nonlinear thin-walled frame element are developed in this study to model the girder. The equivalent modulus of elasticity proposed by Ernst is used for the cable elements. Verification of the present theory is made through a numerical example. Then, the free vibration of a three dimensional cable-stayed bridge is analyzed to study the coupled flexural-torsional behavior.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.1
• /
• pp.75-82
• /
• 1999

일반 해양 구조물이나 해저면에 설치되는 해저 관로는 외력에 의한 변형이 발생된다. 구조물 형상이 복잡하거나, 구성 요소의 개수가 많을 경우 응력해석 시 많은 초기값이 필요하고 해석 시간 또는 장 시간 소요된다. 해양 구조물에 작용하는 대표적인 외력은 파도, 조류, 바람이고 이런 외력은 구조물의 사용 기간(operation life)동안 계속적으로 작용하기 때문에 구조물의 변형율은 항상 허용치 안에서 발생되도록 설계되어야 한다. 허용 변형은 탄성범위 내에 존재해야 하며, 비교적 큰 변형을 일으키는 구조물이나 해저파이프라인의 응력해석을 수치적으로 접근하는 방법을 고찰하였다. 평행상태의 하중 벡터값만 직각 좌표계에서 인트린직(intrinsic) 좌료로 변환시킬 때 변형이 발생함으로, 본 논문에서 소개하는 이차 요소(quadratic element)방법을 사용할 경우 수치해석 시 많은 장점이 있다는 것을 보여준다. 본 방법을 도입함으로써 비교적 큰 변형이 발생되는 구조물 해석 시 일반 수치해석 방법과 그 결과는 같으나 해석 시간을 단축시킬 수 있다는 장점이 있다. 응력 해석 시 국부 강도 행열(element stiffness matrix)은 방향과 무관하며 이차요소 방법을 사용하여 각 요소 벡터를 발생시켰다. 해저관로 일점 상승 시 관로에 작용하는 변형과 상승력에 따른 휨 모멘트를 산출하여 일반적으로 사용되는 선형이론과 비교하였다.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.2
• /
• pp.89-96
• /
• 2017

In this study, CS-H walls with large stiffness were constructed using geosythetics for use in excavation at a depth of 30 m or more in Korea, and in order to construct the CS-H wall suitable for the site conditions, the formulation was examined according to the change in the mixing ratio of the geosythetics and the slump value (slump flow) and as a result, in the target slump 180 mm and the slump flow 500 mm, the formulation was confirmed to meet the mechanical properties such as the initial bending strength, the long-term behavior, and the elastic modulus as well as the economic efficiency. However, in the slump flow 600 mm, the result indicated that the formulation was inappropriate in the mechanical properties such as the initial bending strength, the long-term behavior, and the elastic modulus.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.9
• /
• pp.39-49
• /
• 2007

The load deformation behavior of the cap-pile-soil system is investigated, based on numerical analysis. Special attention is given to consideration of pile cap flexibility. Rigid pile cap analysis and flexible cap analysis were conducted for comparison. A numerical method that takes into account the coupling between the rigidities of the piles, the cap, and the column has been introduced to analyze the response of pile group supported columns. The prediction of the lateral loads and bending moments in the pile cap is much more conservative for a flexible cap than for a rigid cap.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.5
• /
• pp.98-105
• /
• 2018

Cracks in RC members occurred as a result of material and structural factors. The crack width and a crack location are very difficult to examine. A direct crack control method and indirect crack control method to control a crack are presented in the KHBDC (LSD) and KSCDC (2012). In the KSCDC text, cracks are controlled by steel spacing indirectly under a service load. On the other hand, in the KSCDC appendix, cracks are controlled by a crack width directly under a sustained load. In particular, the loading state considered is different. On the other hand, cracks are controlled under a combination of service load and an effective elastic modulus is used in KHBDC. Therefore, in this study, an effective elastic modulus that can reflect the ratio of the sustained load and live load was applied, and a maximum steel spacing was calculated through a design crack width. A variable interpretation was carried out, and a rational crack control method was assessed. As a result, a steel spacing through the design crack width in the KSCDC was smaller than that from the design crack width in the KHBDC, which leads to a conservative design. In addition, the maximum steel spacing suggested in this study has a consistency eliminating the difference between direct crack control and indirect crack control.

• Journal of Korea Foresty Energy
• /
• v.25 no.2
• /
• pp.1-8
• /
• 2006

The physical, mechanical and chemical properties of old and new Korean red pine (Pinus densiflora) were analyzed. The old woods were from dismantled timbers of Bonjungsa temple. The crystallized resin in the latewood was observed by microscopic analysis. Also, reduction of specific gravity, occurrence of microscopic cleavage of tracheid was observed in the old wood. The angle of microscopic cleavage of tracheid is estimated with the same angle of micro-fibril angle of 52 layer. The bending, compression and shear strength of old world were decreased about 35-27% than those of new wood. Dynamic modulus of elasticity measured by ultrasonic nondestructive test has the tendency of reducing by the time elapse of the wood usage. Therefore, deterioration of wood could be measured by reduction of specific gravity and dynamic MOE. The static MOE and mechanical properties of old wood could be predictable by measuring dynamic MOE in the longitudinal direction. Extractives of the old wood in 1-% NaOH solution are larger quantity than new wood. Therefore the decay of the wood could be evaluated by analyzing the chemical compound, especially 1-% NaOH solution. The results of this research could be used for understanding and prediction of the changing properties with elapsing time of wood.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.4
• /
• pp.5-14
• /
• 2016

Numerical simulation of dynamic soil-pile-structure interaction embedded in a dry sand was carried out. 3D model of the dynamic centrifuge model tests was formulated in a time domain to consider nonlinear behavior of soil using the finite difference method program, FLAC3D. As a modeling methodology, Mohr-Coulomb criteria was adopted as soil constitutive model. Soil nonlinearity was considered by adopting the hysteretic damping model, and an interface model which can simulate separation and slip between soil and pile was adopted. Simplified continuum modeling (Kim et al., 2012) was used as boundary condition to reduce analysis time. Calibration process for numerical modeling results and test results was performed through the parametric study. Verification process was then performed by comparing numerical modeling results with another test results. Based on the calibration and validation procedure, it is identified that proposed modeling method can properly simulate dynamic behavior of soil-pile system in dry condition.