• Structural Engineering and Mechanics
• /
• 제68권4호
• /
• pp.475-483
• /
• 2018

Square tubular columns are commonly used in moment resisting frames, while through-diaphragm connection is the most typical configuration detail to connect the H-shaped beam to the column. However, brittle fracture normally occurs at the complete joint penetration weld between the beam flange and the through-diaphragm due to the stress concentration caused by the geometrical discontinuity. Accordingly, three improved types of through-diaphragm are presented in this paper to provide smooth force flow path comparing to that of conventional connections. Tensile tests were conducted on four specimens and the results were analyzed in terms of failure modes, load-displacement response, yield and ultimate capacity, and initial stiffness. Furthermore, strain distributions on the through-diaphragm, the beam flange plate, and the column face were comprehensively evaluated and discussed. It was found that all the proposed three types of improved through-diaphragm connections were able to reduce the stress concentration in the welds between the beam flange and the through-diaphragm. Furthermore, the stress distribution in connection with longer tapered through-diaphragm was more uniform.

• 한국지반공학회지:지반
• /
• 제5권3호
• /
• pp.19-28
• /
• 1989

본문은 전단과정에서 경화되는 모래와 같은 재료의 구성식을 연구하기 위하여 그 기초실험으로서 이미 경화된 콘크리트를 대상으로 3주응력을 독립적으로 제어할 수 있는 입방체삼축추축실험기를 통해 여러가지 응력경로 실험을 실시한 것이다. 실험으로서는 HC, CTC, TC, TE, SS 등 5종이고 그 들의 응력-변형률관계와 강도특성을 8면체면에서 고찰한 것이다. 이들을 통한 주요 결론은 다음과 같다. 1. 경화재료에 대한 전단강도의 크기는 CTC, TC, SS, TE의 순서이다. 2. 8면체전단강도는 응력경로에 의존하고 3. 또한 등방응력이 클수록 좋다. 4. 8면체면에서 극한포락선은 원추형상이다. 5. 마찰성재료인 경화재료에 대해서는 인장강도의 영향을 고려해야 한다.

• Steel and Composite Structures
• /
• 제21권1호
• /
• pp.137-156
• /
• 2016

Due to excellent advantages such as better illuminative effects, considerable material savings and ease and rapidness of construction, the bolted ball-cylinder joint which is a new type joint system has been proposed in space truss structures. In order to reveal more information and understanding on the behaviour of bolted ball-cylinder joints, full-scale experiments on eight bolted ball-cylinder joint specimens were conducted. Five joint specimens were subjected to axial compressive force, while another three joint specimens were subjected to axial tensile force. The parameters investigated herein were the outside diameter of hollow cylinders, the height of hollow cylinders, the thickness of hollow cylinders, ribbed stiffener and axial force. These joint specimens were collapsed by excessive deformation of hollow cylinders, punching damage of hollow cylinders, evulsion of bolts, and weld cracking. The strain distributions on the hollow cylinder opening were mainly controlled by bending moments. To improve the ultimate bearing capacity and axial stiffness of bolted ball-cylinder joints, two effective measures were developed: (1) the thickness of the hollow cylinder needed to be thicker; (2) the ribbed stiffener should be adopted. In addition, the axial stiffness of bolted ball-cylinder joints exhibited significant non-linear characteristics.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1999년도 가을 학술발표회 논문집
• /
• pp.389-396
• /
• 1999

In this study compressive and tensile load tests have been performed to investigate reinforcing effect and load transfer mechanism of small diameter piles installed in the foundation soil for the marine suspension bridge. Load tests were carried out on steel plate with diameters of 50cm, 100cm and 150cm varying loads starting from 39 tons up to 314 tons. Small diameter piles were proved to behavior like as friction piles and loads were not transmitted to the bottom of piles. From pull-out tests, the uplift capacity of small diameter piles was largely influenced by reinforcing materials compared to frictional resistance between piles and adjacent soils. The bearing capacity of small diameter piles appeared to be higher than the ultimate bearing capacity evaluated using static formulae. The load carrying capacity of small diameter piles was superior to the bored piles with a similar size. Thus, ultimate bearing capacity estimated from static formulae can provide conservative designs and thereby resulting in economic disadvantages. A further study to accumulate data regarding various soil conditions is recommended for an improved estimation of bearing capacity of piles with small diameter.

• 한국재난정보학회 논문집
• /
• 제16권4호
• /
• pp.796-805
• /
• 2020

연구목적: I형 강거더의 압축플랜지에 80MPa급의 고강도 콘크리트가 합성된 거더의 극한휨강도 평가를 위하여 정적재하시험을 수행하였다. 연구방법: 본 실험은 전단연결 상세가 다른 2종류의 실험체를 설계 및 제작하여 극한한계상태 도달까지 극한휨거동을 평가하였다. 또 실험 결과와 변형률적합법 결과 비교를 통해 극한강도를 평가하였다. 연구결과: 상대슬립 측정 결과 0.02mm 이내 변위를 확인함으로서 두 실험체가 완전결합을 담보한다는 것을 검증하였다. 따라서 전단상세의 차이는 강성에 큰 영향을 미치지 않으며 완전합성 된다면 극한한계상태까지의 거동에도 차이가 없다. 결론:실험 대상이 되는 거더는 사용하중이 탄성범위 내 있고, 허용처짐에 대한 사용성 요구조건을 충족시킨다. 따라서 케이싱 일부가 균열이 발생하는 수준의 인장력을 받더라도 철근의 역할로 인해 바닥판이 압축 파괴에 먼저 도달한다.

• Geomechanics and Engineering
• /
• 제8권4호
• /
• pp.541-557
• /
• 2015

This research aims to analyze the fracture coalescence characteristics of brittle sandstone specimen ($80{\times}160{\times}30mm$ in size) containing various flaws (a single fissure, double squares and combined flaws). Using a rock mechanics servo-controlled testing system, the strength and deformation behaviours of sandstone specimen containing various flaws are experimentally investigated. The results show that the crack initiation stress, uniaxial compressive strength and peak axial strain of specimen containing a single fissure are all higher than those containing double squares, while which are higher than those containing combined flaws. For sandstone specimen containing combined flaws, the uniaxial compressive strength of sandstone increase as fissure angle (${\alpha}$) increases from $30^{\circ}$ to $90^{\circ}$, which indicates that the specimens with steeper fissure angles can support higher axial capacity for ${\alpha}$ greater than $30^{\circ}$. In the entire deformation process of flawed sandstone specimen, crack evolution process is discussed detailed using photographic monitoring technique. For the specimen containing a single fissure, tensile wing cracks are first initiated at the upper and under tips of fissure, and anti-tensile cracks and far-field cracks are also observed in the deformation process; moreover anti-tensile cracks usually accompanies with tensile wing cracks. For the specimen containing double squares, tensile cracks are usually initiated from the top and bottom edge of two squares along the direction of axial stress, and in the process of final unstable failure, more vertical splitting failures are observed in the ligament region. When a single fissure and double squares are formed together into combined flaws, the crack coalescence between the fissure tips and double squares plays a significant role for ultimate failure of the specimen containing combined flaws.

• 콘크리트학회논문집
• /
• 제14권5호
• /
• pp.638-644
• /
• 2002

본 연구에서는 압축강도 1400 kgf/$\textrm{cm}^2$ 를 갖는 불포화 폴리에스터 폴리머 콘크리트를 이용하여 제작한 C형 시험체에 대한 편심압축 시험을 통하여 폴리머 콘크리트 휨부재의 응력-변형률 관계를 구명하고 등가직사각형 응력블럭의 파라미터 $\alpha$, $\beta$1, ${\gamma}$를 산출하였다. 아울러 인장철근비를 달리하는 5종의 전단스팬비 4.0인 철근 보강 폴리머 콘크리트 보에 대한 휨시험에서 얻어진 극한모멘트 시험값과 C형 시험체 응력-변형률 곡선에서 산출되는 파라미터 $\alpha$=0.61, $\beta$1=0.73 를 이용하여 계산된 이론적인 극한모멘트 값을 비교하여 보았던 바, 인장철근비가 0.50 $\rho$b 이상일때 시험값과 이론값이 비교적 잘 부합됨을 확인 할 수 있었다. 그러나 폴리머 콘크리트 휨 부재에 대한 보다 정확한 설계기준의 마련을 위해서는 압축강도와 크기를 변수로 하는 C형 시험체에 대한 보다 많은 시험을 통한 파라미터의 체계적인 연구가 필요하다.

• 대한토목학회논문집
• /
• 제28권2A호
• /
• pp.289-295
• /
• 2008

본 연구는 탄소섬유판으로 보강된 철근콘크리트 부재의 휨 거동특성 및 파괴양상을 규명하고 또한 탄소섬유판 부착탈락 거동을 규명함에 그 목적이 있다. 이를 위하여 탄소섬유판의 형상, 섬유판 부착길이, 부착면적 등의 다양한 변수를 포함하는 실험연구가 수행되었으며, 초기 부착균열이 발생되는 부착탈락 기구를 규명 하였다. 본 실험결과 탄소섬유판으로 보강된 철근콘크리트 부재의 휨 강성은 보강되지 않은 보에 비해 현저하게 개선되며 최대 극한강도 증진율은 120% 이상인 것으로 나타났다. 또한 탄소섬유판 탈락 시 측정된 탄소섬유판의 인장변형율은 탄소섬유판의 극한 변형율의 36%에 해당되는 것으로 나타났으며, 탄소섬유판의 부착길이가 충분 할수록 보는 휨 균열로 야기되는 탄소섬유판의 계면 부착탈락으로 파괴됨을 알 수 있었다. 탄소섬유판의 계면부착탈락은 휨을 받는 구역에서 시작되어 보의 양 끝단으로 급격하게 전파되는 취성적인 파괴를 유도하는 것으로 나타났다. 본 연구에서는 탄소섬유판의 유효응력에 근거하여 탄소섬유판으로 보강된 철근콘크리트 부재의 휨 강성을 계산하였으며, 이는 실험결과와 잘 일치하는 것으로 나타났다.

• 대한기계학회논문집A
• /
• 제30권11호
• /
• pp.1494-1501
• /
• 2006

Mechanical and physical properties of a copper alloy for a liquid rocket engine(LRE) combustion chamber liner application were tested at various temperatures. All test specimens were heat treated with the condition they might experience during actual fabrication process of the LRE combustion chamber. Physical properties measured include thermal conductivity, specific heat and thermal expansion data. Uniaxial tension tests were preformed to get mechanical properties at several temperatures ranging from room temperature to 600$^{\circ}C$. The result demonstrated that yield stress and ultimate tensile stress of the copper alloy decreases considerably and strain hardening increases as the result of the heat treatment. Since the LRE combustion chamber operates at higher temperature over 400$^{\circ}C$, the copper alloy can exhibit time-dependent behavior. Strain rate, creep and stress relaxation tests were performed to check the time-dependent behavior of the copper alloy. Strain rate tests revealed that strain rate effect is negligible up to 400$^{\circ}C$ while stress-strain curve is changed at 500$^{\circ}C$ as the strain rate is changed. Creep tests were conducted at 250$^{\circ}C$ and 500$^{\circ}C$ and the secondary creep rate was found to be very small at both temperatures implying that creep effect is negligible for the combustion chamber liner because its operating time is quite short.

• 한국안전학회지
• /
• 제23권1호
• /
• pp.1-11
• /
• 2008

In this study, small punch test and tensile test were performed with specimens directly machined from an ASTM A53 grade B carbon steel pipe at which an explosion accident was occurred in the Heavy Oil Unit. Main damage mechanism of the pipe was known as a high temperature hydrogen attack(HTHA). Effects of HTHA on the mechanical strength change of the A53B steel were studied in detail. Small punch test results have showed that maximum reaction forces, SP energy and ductility were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Yield strength and tensile ultimate strength were calculated with the obtained small punch test curve results using different methods and compared the estimation methods. Small punch test simulation has been also performed with the finite element method and then mechanical strength, equivalent strain and fracture toughness were calculated with the obtained numerical analysis results. It was shown that the fracture toughness data calculated from small punch equivalent energy obtained by the finite element analysis for SP test was very low at the hydrogen attacked part.