• 터널과지하공간
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• 제18권3호
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• pp.185-193
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• 2008

이 연구에서는 시추공 분석 작업을 통해 획득된 암반절리 방향성이 심도에 따라 변화하는 양상의 확인을 위해 피어슨 카이제곱 통계검정이 실시되었다. 대상 암반은 모암이 화강암질 편마암인 두 지역으로서, 이와같은 엽리가 발달하지 않은 괴상의 암상 선정은, 엽리가 존재하는 암석의 경우 절리 방향성이 엽리에 의해 영향을 받고 엽리의 방향은 습속 등의 지질작용에 의해 심도에 따라 다를 수가 있기 때문이다. 암반 절리들의 방향 파악을 위해 시추공 영상이 이용되었다. 획득된 방향자료를 천부구간과 심부구간의 자료로 분류한 후 21 영역으로 구성된 분할망에 각각 투영 후, 분류표를 작성하여 통계검정을 실시하였으며, 분석결과 두 지역 중 한 지역의 자료는 비동질로 나타났다. 이러한 결과는 터널과 같은 지하구조물의 설계를 위한 암반공학적으로 중요한 절리면의 방향성에 대한 조사시 원위치 조사가 바람직함을 시사한다.

• 한국강구조학회 논문집
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• 제21권1호
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• pp.55-62
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• 2009

강교 제작에는 강재 표면의 이물질 제거와 피복방식재료의 부착성 증대를 위하여 블라스트 표면처리가 실시되고 있다. 블라스트 표면처리는 쇼트나 그릿 등의 연마재를 압축공기로 분사하여 강재 표면에 충격을 가하는 표면처리법으로, 블라스트 처리에 의해 표면형상이 개선되고 압축잔류응력이 도입되어 용접이음의 피로수명이 향상될 것으로 예상된다. 본 연구에서는 하중비전달형 십자필렛 용접이음의 피로실험을 실시하여, 블라스트 표면처리가 용접이음의 피로거동에 미치는 영향을 실험적으로 검토하였다. 피로실험에는 용접 후 무처리 시험편(용접 그대로), 용접 후 블라스트 표면처리 한 시험편과 블라스트 처리 후 열처리에 의해 잔류응력을 제거한 시험편의 합계 3종류의 용접시험편을 대상으로 하였다. 그 결과 블라스트 표면처리에 의해 용접지단부의 곡률반경은 약 29% 증가하였으며, 용접지단부의 인장잔류응력이 제거되고 압축잔류응력이 도입되었다. 그리고 블라스트 처리에 의해 피로수명과 피로한계가 증가하였다. 피로수명은 응력범위가 낮을수록 더 크게 증가하였고, 피로한계는 약 1.5배 증가하였다.

• 한국자동차공학회논문집
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• 제21권1호
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• pp.145-153
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• 2013

In this study, shear punch-creep (SP-Creep) at Sn-4Ag/Cu pad the joint was tested by using environment-friendly Pb-free solder alloy Sn-4Ag of electronic components. Pb eutectic alloy (Sn-37Pb) joints limited to environmental issues with reflow time (10sec, 30sec, 100sec, 300sec) according to two types of solder alloy joints are compared and evaluated by creep strain rate, rupture time and IMC (Intermetallic Compound) behavior. As the results, reflow time increases with increasing thickness of IMC can be seen at overall 100sec later in case of two solder joints on the IMC thickness of Sn-4Ag solder joints thicker than Sn-37Pb solder joints. In addition, when considering creep evaluation factors, lead-free solder alloy Sn-4Ag has excellent creep resistance more than Pb eutectic alloy. For this reason, the two solder joints, such as in the IMC (Cu6Sn5) was formed. However, the creep resistance of Sn-4Ag solder joints was largely increased in the precipitation strengthening effect of dispersed Ag3Sn with interface more than Sn-37Pb solder joints.

• Steel and Composite Structures
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• 제19권6호
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• pp.1561-1580
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• 2015

No significant improvement has been observed on the seismic performance of the ordinary steel reinforced concrete (SRC) columns compared with the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type section steel were put forward on this background: a cross-shaped steel whose flanges are in contact with concrete cover by extending the geometry of webs, and a rotated cross-shaped steel whose webs coincide with diagonal line of the column's section. The advantages of new-type SRC columns have been proved theoretically and experimentally, while construction measures and seismic behavior remain unclear when the new-type columns are joined onto SRC beams. Seismic behavior of SRC joints with new-type section steel were experimentally investigated by testing 5 specimens subjected to low reversed cyclic loading, mainly including the failure patterns, hysteretic loops, skeleton curves, energy dissipation capacity, strength and stiffness degradation and ductility. Effects of steel shape, load angel and construction measures on seismic behavior of joints were also analyzed. The test results indicate that the new-type joints display shear failure pattern under seismic loading, and steel and concrete of core region could bear larger load and tend to be stable although the specimens are close to failure. The hysteretic curves of new-type joints are plumper whose equivalent viscous damping coefficients and ductility factors are over 0.38 and 3.2 respectively, and this illustrates the energy dissipation capacity and deformation ability of new-type SRC joints are better than that of ordinary ones with shear failure. Bearing capacity and ductility of new-type joints are superior when the diagonal cross-shaped steel is contained and beams are orthogonal to columns, and the two construction measures proposed have little effect on the seismic behavior of joints.

• Steel and Composite Structures
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• 제44권1호
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• pp.33-47
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• 2022

This paper presents a finite element model for predicting the monotonic behaviour of bolted endplate joints connecting steel-concrete composite walls and steel beams. The demountable Hollo-bolts are utilised to facilitate the quick installation and dismantling for replacement and reuse. In the developed model, material and geometric nonlinearities were included. The accuracy of the developed model was assessed by comparing the numerical results with previous experimental tests on hollow/composite column-to-steel beam joints that incorporated endplates and Hollo-bolts. In particular, the Hollo-bolts were modelled with the expanded sleeves involved, and different material properties of the Hollo-bolt shank and sleeves were considered based on the information provided by the manufacture. The developed models, therefore, can be applied in the present study to simulate the wall-to-beam joints with similar structural components and characteristics. Based on the validated model, the authors herein compared the behaviour of wall-to-beam joints of two commonly utilised composite walling systems (Case 1: flat steel plates with headed studs; Case 2: lipped channel section with partition plates). Considering the ease of manufacturing, onsite erection and the pertinent costs, composite walling system with flat steel plates and conventional headed studs (Case 1) was the focus of present study. Specifically, additional headed studs were pre-welded inside the front wall plates to enhance the joint performance. On this basis, a series of parametric studies were conducted to assess the influences of five design parameters on the behaviour of bolted endplate wall-to-beam joints. The initial stiffness, plastic moment capacity, as well as the rotational capacity of the composite wall-to-beam joints based on the numerical analysis were further compared with the current design provision.

• Geomechanics and Engineering
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• 제29권4호
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• pp.471-486
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• 2022

The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').

• 대한토목학회논문집
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• 제30권2A호
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• pp.113-120
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• 2010

콘크리트 충전강관을 이용한 교량은 새로운 형식의 교량 형태이다. 강관을 이용한 교량을 적용하는데 있어서 가장 중요한 것은 이음부의 설계이다. 이 논문에서는 축하중을 받는 충전강관 N형 이음부에서 현재는 충전강관으로 브레이스는 강관으로 구성된 이음부의 특성을 범용 프로그램인 ABAQUS를 이용하여 유한요소해석을 통해 고찰하였다. 충전강관 이음부의 핫스폿 응력을 결정하는 기하학적 인자 중, 용접 각장길이, 현재의 직경, 브레이스의 두께에 따른 핫스폿 응력의 차이점을 비교하였다. 또한 충전강관 N형 이음부에서 사재의 각도와 수직재와 사재사이의 거리를 변수로 하여 유한요소해석을 수행하였으며, 현재에 충전된 콘크리트의 강도의 변화에 따른 이음부의 핫스폿 응력 특성을 살펴보았다.

• 콘크리트학회논문집
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• 제24권3호
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• pp.275-283
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• 2012

초고층 건축물의 선행 코어 후행 슬래브 접합부, 지하 연속벽과 바닥구조의 접합부, 임시 개구부 등 신구 콘크리트 접합부의 철근 이음을 위하여, 다수의 커플러를 전단키가 있는 얇은 강판에 설치한 철근 이음용 매립 강판이 최근 개발되었다. 이 공법을 사용한 접합부의 구조 성능을 검증하기 위하여, 벽체-슬래브 접합부에 대한 반복하중 실험을 실시하였다. 비교를 위해 기존에 사용되는 굽힌 철근 박스를 이용한 접합부와 이음이 없는 접합부도 함께 실험하였다. 실험 결과 철근 이음용 매립 강판을 사용한 접합부는 이음이 없는 접합부와 동일하게 [인장철근 항복]-[충분한 휨변형]-[압축 콘크리트 압괴] 후 압축 철근의 좌굴로 파괴되었다. 따라서 설계에서 가정한 충분한 연성 거동을 확인할 수 있었다. 반면, 굽힌 철근 박스를 사용한 접합부의 경우, 탄성구간에서는 철근 이음용 매립 강판과 유사하게 거동하였으나, 측면 피복 콘크리트가 빨리 탈락되었으며, 슬래브 상하부면의 겹침이음 구간에 부착 균열이 다수 발생하였다. 최종적으로 이음 없는 실험체 및 철근 이음용 매립 강판을 사용한 실험체에 비해 강도와 변형능력이 저하되었다. 또한 굽힌 후편 철근을 겹침이음한 실험체가 철근 이음용 매립 강판을 적용한 경우에 비해 강성 저하가 빠르게 진행되었다. 굽힌 후편 철근의 탄성계수는 직선 철근에 비해 낮고, 완전한 직선으로 펼 수 없기 때문에 인장력을 받으면서 일부 구간이 펴지므로 접합부의 강성을 저하시킨 것으로 판단된다. 2종류의 철근 지름(D13, D16)과 강종(SD300, SD400)에 대해, 철근이음용 매립 강판을 적용한 접합부는 공칭 강도를 충분히 상회하였다. 그러나 굽힌 후 편 철근을 사용하면 강종이 높을수록 그리고 지름이 굵을수록 휨강도가 저하되었다. 따라서 굽힌 후 편 철근의 사용에 주의가 필요하다.

• 한국생산제조학회지
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• 제7권1호
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• pp.58-68
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• 1998

Advantages of adhesively bonded joints and techniques of weight reduction have led to increasing use of structural adhesives such as LSI(large scale integration) package, automobile, aircraft in the various industries. In spite of such wide applications of adhesively bonded joints, the evaluation method of bonding strength has not been established. Stress singularity occurs at the interface edges of adhesively bonded joints and it is required to analyze it. In this paper, the stress singularity using 2-dimensional elastic boundary element method (BEM) with the changes of the lap length and adhesive for single lap joint was analyzed, and experiments of strength evaluation were carried out. As the results, the evaluating method of bonding strength considering stress singularity at interface edges of adhesively bonded joints and stress intensity factor of interface crack have been proposed in static and fatigue test.

• Advances in concrete construction
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• 제10권1호
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• pp.21-34
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• 2020

Precast deck joints have larger crack width than cast-in-place concrete decks. The initial crack typically occurs at the maximum moment but cracks on precast joints are significant and lead to failure of the deck. The present crack equation is applied to cast-in-place decks, and requires correction to calculate the crack width of precast deck joints. This research aims to study the crack width correction equation of precast decks by performing static tests using high strength and normal strength concrete. Based on experimental results, the bending strength of the structural connections of the current precast deck is satisfied. However it is not suitable to calculate and control the crack width of precast loop connections using the current design equation. A crack width calculation equation is proposed for crack control of precast deck loop joints. Also included in this paper are recommendations to improve the crack control of loop connections.