• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.139-150
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• 1996

H/T(High Tension) bolt is generally being used in joining the members of steel structure. It has some difficulties in management such as an adequate fastening force and a selection of proper instrument for fastening. T/S(Torque Shear Type High Tension) bolt which is more convenient and easier than H/T bolt in quality control has recently been developed. T/S bolts are produced and widely used these days in domestic, but those have not a detail regulation for their on. Those are only being used according to the specification for the H/T bolts. In this study, we tried to confirm the soundness of T/S bolts by the fatigue test of the modified specimens. First, we measured the reduction rate of the initial axial force with time at bolts. Second, we investigated the slip forces of bolts when the test specimen is loaded in tension. Third, we implemented the fatigue tests. During the test, we measured the variation of the axial forces of bolts under the cyclic loading. Finally, we compared and analyzed the fatigue behavior of H/T and T/S bolt, by S-N curve diagrams that are obtained in this study.

• 한국안전학회지
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• 제23권4호
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• pp.19-24
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• 2008

This paper presents and discusses the experimental results on the F10T high strength bolts used in the T-flange joint structure. The experimental works were carried out for the parameters which are flange web thickness, the distance between bolts, prying ratio. The results show that the working stress imposed to bolts decreases as the flange web thickness increases on the other hand the imposed stress to the bolts increases as the distance between two bolts increases. In other words the strength of the T-flange joint increased as the web flange thickness increases and the distance between two bolts decreases. The prying ratio is increased as the distance between two bolts increases and as the flange web thickness decreases However, the degree of stress decrease in flange thickness variation is not that high as the distance variation between two bolts. Finally the equation for predicting the failure stress in T-flange joint structure using F10T high strength bolts was suggested.

• 한국정보통신학회논문지
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• 제13권5호
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• pp.937-943
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• 2009

본 논문에서는 영상 처리를 이용하여 차체의 진동에 영향을 미치는 자동차 T-Bar부품에서의 볼트와 너트의 존재 유무를 판별하는 알고리즘이 소개된다. T-Bar의 볼트와 너트 존재 유무를 판별하기 위하여 볼트와 너트의 특징치들이 학습되고 통계적 패턴매칭 방법을 이용하여 학습된 특징치들이 매칭된다. 또한 영상마다 볼트와 너트들의 화소값이 크게 변화하여 매칭율이 낮아지기 때문에 화소값의 최대와 최소 변화률이 이용된다. 본 논문에서 제안한 방법은 기존의 방법들에 비해 검사시간을 대폭 축소시켜 실시간이 요구되는 검사 자동화 분야에 아주 효율적이다.

• 소성∙가공
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• 제30권4호
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• pp.165-171
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• 2021

This study was conducted on the manufacturing method of high-strength aluminum bolts. We obtained the displacement-load information by tensile test of the Al 6056 raw material and the T6 heat-treated material and calculated the precise flow stress and fracture limit using repetitive finite element analysis for before and after heat treatment. We designed a multi-stage forging process for T6 heat-treated material, and calculated that the accumulated damage value does not exceed fracture limits by finite element method. We produced the prototype forgings without any harmful defects such as cracks and folding occurring. Bolts made of T6 heat treated material show 9.6%higher tensile strength than T6 heat treated material after wire drawing.

• 한국강구조학회 논문집
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• 제11권2호통권39호
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• pp.109-116
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• 1999

본 논문은 관통형 고력볼트를 사용한 엔드플레이트형식 콘크리트 충전 각형 강관 기둥 H형강 보 접합부에 대한 단조가력하에서의 실험적 연구이다. 본 실험의 목적은 전회(前回)에서는 파악되지 않았던 엔드플레이트의 두께와 볼트의 배열에 대한 영향을 정확하게 평가하는데 있다. 실험의 주요변수는 엔드플레이트의 두께(12mm, 16mm)와 볼트의 배열 (EP1, EP2, EP3)이다. 변수에 따른 실험결과를 비교, 분석하였다. 1)실험체는 Bjorhovde와 EC3의 분류법에 의해 분류하였다. 2)T-stub모델에 근거한 접합부의 최대 모멘트 예측식에 의해 계산된 이론치$(_tM_u)$는 실험치$(_eM_u)$에 잘 대응하였다.

• 한국강구조학회 논문집
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• 제28권2호
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• pp.121-128
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• 2016

고장력 볼트를 적용한 원형단면 콘크리트 충전 강재 기둥-기초 연결부의 합리적인 설계범위를 제안하기 위하여 축하중과 수평하중을 동시에 받는 기둥-기초 연결부의 전반적인 구조적 거동과 설계변수에 따른 거동특성을 상용 유한요소해석 프로그램인 ABAQUS를 이용하여 해석적으로 검토하였다. 이를 위해 앵커볼트를 고장력 볼트로 대신하는 선행연구의 실험을 토대로 수치해석을 실시하였으며, 해석방법의 타당성을 검증하였다. 또한 현행 설계기준을 분석하여 기둥-기초 연결부 거동에 영향을 미치는 설계변수(앵커의 묻힘깊이, 앵커의 강종, 리브의 높이, 리브의 두께)를 선정하였으며, 설계변수에 따른 기둥-기초 연결부의 거동특성을 비교 분석하였다. 일반 앵커에 비해 고장력 볼트를 적용하는 것이 기둥-기초 연결부의 거동에 유리한 것으로 나타났으며, 고장력 볼트의 최소 묻힘깊이는 기둥 직경(D)을 기준으로 0.5D이상으로 설계하는 것이 합리적이라고 판단된다. 리브의 높이는 0.5D이상, 리브의 두께는 베이스플레이트 두께($t_b$)를 기준으로 $0.4t_b$이상으로 설계하는 것이 합리적이라고 판단된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.80-81
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• 2009

Ti-6Al-4V alloy has been widely used for aerospace and power generation applications because of low density and attractive mechanical and corrosion resistant properties. However, the titanium alloy bolt is generally manufactured by cutting and rolling because of their poor workability. In order to achieve the mass production of titanium alloy bolts, it needs to be solved some manufacturing problems such as the sticking between workpiece and dies, the formation of the forming defects during the forging and so on. In this study, the manufacturing technology of titanium alloy bolts using warm forging process was introduced. The aim of present work is to develop a warm forging technology for high strength Ti-6Al-4V bolts.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1262-1267
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• 2003

TF magnet structures are the main structural components in the KSTAR magnet systems to protect the superconducting coils from mechanical, electrical, and thermal loads. TF coil structure supports CS and PF coil system. The inter-coil structure contains adjustable shear keys and conical bolts to provide pre-loading in toroidal direction and to resist against in-plane and out-of-plane forces that are the most critical loads on the TF magnet system. The conical bolts and shear keys are specially designed to assemble easily and to provide a convenient accommodation for a good alignment. The connection plate that is one of the prototype fabrications had been manufactured to study adjustability of conical bolts and shear keys for assembly of TF coil structure. We could measure the misalignments at the keyways and conical holes with the misalignment measuring instrument.

• Smart Structures and Systems
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• 제32권1호
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• pp.23-35
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• 2023

Steel bolted joint is an important part of steel structure, and its damage directly affects the bearing capacity and durability of steel structure. Currently, the existing research mainly focuses on the identification of corroded bolts and corroded bolts respectively, and there are few studies on multiple states. A detection framework of corroded and loosened bolts is proposed in this study, and the innovations can be summarized as follows: (i) Vision Transformer (ViT) is introduced to replace the third and fourth C3 module of you-only-look-once version 5s (YOLOv5s) algorithm, which increases the attention weights of feature channels and the feature extraction capability. (ii) Three states of the steel bolts are considered, including corroded bolt, bolt missing and clean bolt. (iii) Line segment detector (LSD) is introduced for bolt rotation angle calculation, which realizes bolt looseness detection. The improved YOLOv5s model was validated on the dataset, and the mean average precision (mAP) was increased from 0.902 to 0.952. In terms of a lab-scale joint, the performance of the LSD algorithm and the Hough transform was compared from different perspective angles. The error value of bolt loosening angle of the LSD algorithm is controlled within 1.09%, less than 8.91% of the Hough transform. Furthermore, the proposed framework was applied to fullscale joints of a steel bridge in China. Synthetic images of loosened bolts were successfully identified and the multiple states were well detected. Therefore, the proposed framework can be alternative of monitoring steel bolted joints for management department.

• Steel and Composite Structures
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• 제16권6호
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• pp.611-637
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• 2014

A single plate shear connection, or shear tab, is a very popular shear connection due to its merit in ease of construction and material economy. However, problems in understanding the connection behavior, both in terms of strength and ductility, have been well-documented. Suggestions or design model for single plate connections in AISC Design Manual have been altered several times, with the latest edition settling down to giving designers pre-calculated design strength tables if the connection details agree with given configurations. Results from many full-scale tests and finite element models in the past suggest that shear strength of a bolt group in single plate shear connections might be affected by yield strength of plate material; therefore, this research was aimed to investigate and clarify effects of plate yield strength and thickness on shear strength of the bolt group in the connections, including the validity of using a plate thickness/bolt diameter ratio ($t_p/d_b$) in design, by using finite element models. More than 20 models have been created by using ABAQUS program with 19.0- and 22.2-mm A325N bolts and A36 and Gr.50 plates with various thicknesses. Results demonstrated that increase of plate thickness or plate yield strength, with the $t_p/d_b$ ratio remained intact, could significantly reduce shear strength of the bolt group in the connection as much as 15 percent. Results also confirmed that the $t_p/d_b$ ratio is a valid indicator to be used for guaranteeing strength sufficiency. Because the actual ratio recommended by AISC Design Manual is $t_p/d_b$ + 1.6 (mm) for connections with a number of bolts less than six and plate yield strength in construction is normally higher than the nominal value used in design, it is proposed that shear strength of a bolt group in single plate connections with a number of bolts equal or greater than seven be reduced by 15 percent and the $t_p/d_b$ ratio be limited to 0.500.