Tension–Shear Experimental Analysis and Fracture Models Calibration on Q235 Steel

Xiaogang Huang,Zhen Zhou,Yazhi Zhu,Dongping Zhu,Lu Lu 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.5

Tension–shear loading is a common loading condition in steel structures during the earthquake shaking. To study ductile fracture in structural steel under multiple stress states, experimental investigations on the diff erent fracture mechanisms in Chinese Q235 steel were conducted. Diff erent tension–shear loading conditions achieved by using six groups of inclined notch butterfl y confi gurations covering pure shear, tension–shear and pure tension cases. Numerical simulations were carried out for all the specimens to determine the stress and strain fi elds within the critical sections. Two tension–shear fracture models were calibrated based on the hybrid experimental–numerical procedure. The equivalent fracture strain obtained from the round bar under tensile loading was used for evaluating these two models. The results indicated that the tension–shear criterion as a function of the shear fracture parameter had better performance in predicting the fracture initiation of structural steel under diff erent loading conditions.

전단하중의 크기가 모드 Ⅱ 분기균열의 형성과 전파에 미치는 영향

이정무(J. M. Lee),송삼흥(S. H. Song) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

In this paper, we investigated the characteristics of initiation and propagation behavior for fatigue crack observed by changing various shapes of initial crack and magnitudes of loading in modified compact tension shear(CTS) specimen subjected to shear loading. In the low-loading condition, the secondary fatigue crack was created in the notch root due to friction on the pre-crack face grew to a main crack. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Influenced by the shear loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. The propagation path of fatigue crack under the Mode II loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

전단하중 하의 피로균열 전파거동의 특징

이정무(Jeong-Moo Lee),송삼홍(Sam-Hong Song) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

This paper reviewed characteristics of fatigue crack behavior observed by changing various shapes of initial crack and magnitudes of loading in compact tension shear(CTS) specimen subjected to shear loading. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Meanwhile, the secondary fatigue crack in the low-loading condition which was created in the notch root due to friction on the pre-crack face grew to a main crack. Influenced by the mode II loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. Propagation path of fatigue crack under the shear loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

전단류 하중을 받는 상부장력 라이저의 동적 응답 해석

김국현(Kookhyun Kim) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.4

A numerical scheme based on a mode superposition method is presented for the dynamic response analysis of a top?tensioned riser (TTR) under sheared current loads. The natural frequencies and mode shapes of the TTR have been calculated analytically for a beam with a slowly varying tension and pinned?pinned boundary conditions at the top and bottom ends. The lift coefficients and corresponding amplitudes used to estimate the vortex?induced modal force and damping for each mode were predicted via iterative calculations based on the input and output power balancing concept. Here, the power?in regions were controlled by the normal distribution function, for which the center was coincident with the lock ?in location by local vortex?shedding, and the range was defined by the constant standard deviation for the reduced velocity by the local current speed. Finally, dynamic responses such as root?mean?squared displacement and stress were calculated using the mode superposition technique. In order to verify the presented scheme, a numerical calculation was performed for a TTR under an arbitrary linearly sheared current and linearly varying tension. A comparison with the results of the existing software showed that the presented scheme could give reliable and feasible solutions. Case studies were performed to investigate the effects of various current loads and tensions.

Fatigue Crack Propagation Behavior in STS304 Under Mixed-Mode Loading

Lee, Jeong-Moo,Song, Sam-Hong The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.6

The use of fracture mechanics has traditionally concentrated on crack growth under an opening mechanism. However, many service failures occur from cracks subjected to mixed-mode loading. Hence, it is necessary to evaluate the fatigue behavior under mixed-mode loading. Under mixed-mode loading, not only the fatigue crack propagation rate is of importance, but also the crack propagation direction. In modified range 0.3$\leq$a/W$\leq$0.5, the stress intensity factors (SIFs) of mode I and mode II for the compact tension shear (CTS) specimen were calculated by using elastic finite element analysis. The propagation behavior of the fatigue cracks of cold rolled stainless steels (STS304) under mixed-mode conditions was evaluated by using K$\_$I/ and $_{4}$ (SIFs of mode I and mode II). The maximum tangential stress (MTS) criterion and stress intensity factor were applied to predict the crack propagation direction and the propagation behavior of fatigue cracks.

자동차 차체 점 용접부 특성에 관한 연구

나의균(Euigyun Na),오석형(SeokhyungOsh),김장권(Jangkweon Kim),김연직(YoenjigKim) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.5-2

The purpose of this study is to examine the characteristics of the spot weld region for the car body. Steel used was ss41 with cold work and 0.8mm of thickness. Spot weld was conducted in air. Finite element method(FEM) and experiment were conducted to investigate the characteristics of the spot weld region. Basic data against the steel were composed of the relations of the specific heat, conductivity, and temperature. Software used was SYS-weld. Node and mesh was made. Tension - shearing test was conducted against the spot weld specimens. Sputtering phenomena occurred at the initial spot weld stage which causes the inappropriate and poor weld for the car body. Residual stresses were produced around the spot weld region and maximum value was located 4mm away from the weld center. It was verified that maximum load around the spot weld region was dependent upon the weld current through the tension-shearing test.

Wire tension 측정을 위한 Pin type Load-cell 개발

백인석(I. S. Pack),이동욱(D. W. Lee),이석순(S. S. Lee),이계광(K. K. Lee),김인환(I. H. Kim),허남수(N. S. Hur) 한국정밀공학회 2013 한국정밀공학회 학술발표대회 논문집 Vol.2013 No.10월

철근콘크리트 보의 극한해석

김태형,김운학,신현목 한국콘크리트학회 1995 콘크리트학회지 Vol.7 No.1

본 논문에서는 단조증가하중을 받는 철근콘크리트 보의 비선형거동, 즉, 탄성, 비탄서의 극한영역에 이르기까지의 모든 하중이력에 대한 응력-변형도 관계와 균열의 진행 및 철근과 콘크리트의 응력과 변형도 등을 정확히 해석할 수 있는 해석법의 제시를 목적으로 한다. 이러한 목적을 위하여 철근콘크리트의 재료적 비선형성으로 균열발생후 이장, 압축 및 전단모델과 철근에 대한 모델을 각각 조합하여 고려하였다. 콘크리트의 해석모델로서 분산균열모델을 사용하였고, 철근에 대해서는 등가의 분산분포된 요소와 철근의 정확한 거동과 위치를 확보하기 위해 별도의 축력만을 받는 봉요소로 모델화하여 사용하였다. 본 논문에서 제안한 해석법의 타당성을 검증하기 위해 몇 개의 실험치를 해석치와 비교, 검토한 결과, 본 논문의 해석법이 3.5-15(%)의 오차를 보이며, 정확함을 알 수 있었다. The purpose of this paper is to present an analysis method which can exactly analyze load-deflection relationships. crack propagations and stresses and strains of steel reinforccnlent and concrete in hehaviors of elastic, mclastic and ultlmate ranges of reinforced concretc beams under monotonically increasing loads. For these purposes, the material nonlinearities are taken into account by comprising the tension. compression and shear models of cracked concrete and a model for reinforcement in the concrete. Smeared crack model is used as a modeling of concrete. The steel reinforcement is assumed to be in an uniaxial stress state and modeled srncaretl layers of eqivalent thickness and line elernents for correct positiori arid behavior. For the verification of application and validity of the method proposed in this paper, several numerical examples are analyzed and compared with those from other researchers. As a results, this method shown in 3.5-15(%) error is correct.

전단링을 사용한 고장력볼트 이음부의 역학적 특성에 관한 연구

이승용(Lee Seung Yong),박영훈(Park Young Hoon) 대한토목학회 2006 대한토목학회논문집 A Vol.26 No.2A

강구조물의 대표적인 현장이음방식인 고장력볼트 마찰이음은 볼트 축력의 관리가 엄격하기 때문에 많은 노동력과 시간을 필요로 하며, 미끄러짐 하중을 기준으로 설계가 이루어져 볼트의 높은 전단강도를 유효하게 이용하지 못하고, 그 결과 소요 볼트수가 많아지는 단점이 있다. 따라서 고장력볼트 마찰이음의 단점을 보완하고, 지압이음의 장점을 살린 전단링을 시용한 새로운 이음방식을 개발하여 기존의 고장력볼트 마찰이음과 비교실험을 실시하고 해석적 연구를 실시하였다. 그 결과 전단링을 이용한 새로운 이음방식은 전단링의 높은 전단강도로 저항하기 때문에 기존의 마찰이음보다 이음부의 내력이 크게 향상되는 것을 실험적으로 확인할 수 있었다. 한편 전단이음의 응력집중을 최소화하면서 최대의 연결강도를 유도하기 위해서는 전단링의 깊이 등의 설계 변수에 대한 추가적인 연구가 필요할 것으로 판단된다. Friction type high tension bolted joints is one of the most common steel structure connections and requires significant concerns on axial force of the bolts. However, its high shear capacity is not appropriately considered in design and hence the number of bolts is over-designed than actually required. It is primarily due to a slip-load-based design method. This study, therefore, suggests a new technology of connection using a shear ring, which may reduce the shortcomings from the friction-typed high tension bolted joints and maximize the advantages from the bearing-typed joints. Experimental and numerical studies were performed to compare the capacity of the suggested method with traditional high tension bolted joints. From the results, it is known that the suggested connections has higher bearing capacity than friction-typed high tension bolted joints due to the higher shear resistance from the ring. For further study, it may be necessary to investigate on design parameters including the depth of shear ring, for increased connection capacity.

격자형 강합성 바닥판 이음부의 하중전달 거동에 관한 실험적 연구

신현섭 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.4

프리캐스트 방식에 의해 제작이 가능한 격자형 강합성 바닥판의 이음부는 콘크리트 전단키와 고장력볼트 체결로 구성될 수 있으며, 이와같은 이음부 자체에 대한 휨 및 전단성능은 부재요소에 대한 실험을 통해 분석된 바 있다. 본 연구에서는 실제 바닥판 구조시스템에서 이음부에 의한 횡방향 하중전달 거동을 분석하고자, 길이 2.5m 및 폭 1m의 단위 바닥판 모듈 한쌍에 이음부를 설치한 실험체를 제작하고 중심 및 편심가력 휨실험을 하였다. 이음부에 하중이 직접 가해지는 중심재하 조건에서 고장력볼트의 설치개수가 30cm 간격 9개에서 60cm 간격 4개로 줄어 들 경우, 재하단계에 따라 이음부의 회전이 비교적 더 크게 증가하고, 이에 따라 바닥판 횡방향으로의 하중전달 정도가 감소함을 알 수 있었다. 그러나, 한쪽 바닥판의 중심에 집중하중이 가해지는 편심재하 조건의 경우에는 횡방향 하중전달 거동에 큰 차이가 없었다. 하중 재하방법별로 이음부의 거동을 비교한 결과, 집중하중에 대한 바닥판 횡방향으로의 하중분배 및 전달량은 이음부 자체의 성능뿐만 아니라 바닥판 슬래브의 펀칭전단에 의해서도 제한되는 것으로 분석되었다. 또한, 펀칭 전단파괴가 발생할 때까지 이음부의 고장력볼트가 항복하지 않은 점을 고려할 때, 이음부 고장력볼트의 설치개수를 4개에서 9개로 증가시키는 것은 실질적으로 강도 보다는 이음부 및 바닥판의 휨강성 성능 증가에 더 큰 영향을 미치는 것으로 사료된다. The joint of prefabricated steel grid composite deck is composed of concrete shear key and high-tension bolts. The flexural and shear strength of the joint were experimentally evaluated only by the bending and push-out test of the joint element. In this study the lateral load transfer behavior of the joint in deck structure system is experimentally evaluated. Several decks connected by the joint are prefabricated and loaded centrically and eccentrically. In the case of centrically loaded specimens, the analysis results show that for the same loading step the rotation angle of the joint with 4 high-tension bolts is larger than the case of the joint with 9 high-tension bolts. Consequently, flexural stiffness of deck and lateral load transfer decrease in the case of specimen with 4 high-tension bolts. But, in the case of eccentrically loaded specimens, it is found that there are no significant differences in the load transfer behavior. The further analysis results about the structural behavior of the joint show that lateral load transfer can be restricted by the load bearing capacity of the joint as well as punching shear strength of the slab. Furthermore, considering that high-tension bolts in the joint didn't reach to the yielding condition until the punching shear failure, increase in the number of high-tension bolts from 4 to 9 has a greater effect on the flexural stiffness of the joint and deck system than the strength of them.