터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측 한국지반공학회논문집 제26권 제6호터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측

박두희,신종호,윤세웅 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.6

Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

단일 현장타설말뚝의 가상고정점 설계 및 분리해석 적용성 평가

김재영,정상섬 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.7

In this study, the virtual fixed point analysis and 3D full-modeling analysis for pile bent structures are conducted by considering various influencing factors and the applicability of the virtual fixed point theory is discussed. Also, a discrete analysis calculating separately both the superstructure and substructure of pile bent structures is performed on the basis of an equivalent base spring model by taking into account the major influencing parameters such as soil conditions, combined loading and pile diameter. The results show that the settlement and lateral deflection of the virtual fixed point theory are smaller than those of 3D full-modeling analysis. On the other hand, the virtual fixed point analysis overestimates the axial force and bending moment compared with 3D full-modeling analysis. It is shown that the virtual fixed point analysis cannot adequately predict the real behavior of pile bent structures. It is also found that discrete analysis gives similar results of lateral deflection and bending moment to those of unified analysis. Based on this study,it is found that discrete analysis considering column-pile interaction conditions is capable of predicting reasonably well the behavior of pile bent structures. It can be effectively used to perform a more economical design of pile bent structures.

벨로우즈형 신축관이음의 휨각도 예측 및 이를 이용한 배관계의 안정성 해석

손인수,Son, In-Soo 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.5

In this study, the prediction of the bending angle for the 350 A bellows-type expansion joints and the structural stability according to the load were determined. The stability of the 2km piping system was predicted by applying the allowable bending angle of the expansion pipe joint obtained from the analysis. The maximum bending angle was calculated through bending analysis of the bellows-type expansion joints, and the maximum bending angle by numerical calculation was about 1.8°, and the maximum bending angle of the bellows obtained by comparing the allowable strength of the material was about 0. 22°. This angle was very stable compared to the allowable bending angle (3°) of the expansion pipe joint regulation. By applying the maximum bending angle, the allowable maximum deflection of the 2 km pipe was about 3.8 m. When the seismic load was considered using regression analysis, the maximum deflection of the 2km pipe was about 142.3mm, and it was confirmed that the bellows-type expansion joints and the deflection were stable compared to the allowable maximum deflection of the pipe system. These research results are expected to present design and analysis guidelines for the construction of piping and the development of bellows systems, and to be used as basic data for systematic research.

유한요소해석을 이용한 박판 벤딩용 CO₂ 레이저 성형기 제작

고대철,이찬주,김병민,Ko D.C.,Lee C.J.,Kim B.M. 한국소성가공학회 2006 소성가공 : 한국소성가공학회지 Vol.15 No.4

The laser forming process is a new flexible forming process without forming tools and external force, which is applied to various fields of industry. Especially, applications of the laser forming process focused on cutting, welding and marking process. In this paper, the laser bending process of sheet metal which is heated by laser beam and formed by internal stress is simulated by using thermo elastic-plastic analysis model. Based on the result of FE-analysis, the laser bending machine is made to obtain reliable data for sheet bending. Under the same condition as FE-analysis, the laser bending experiment has been performed to ver 펴 the result of FE-analysis and good agreement has been obtained between FE-analysis and experiments. Additional laser bending experiments have been performed to evaluate the laser bending machine.

Limit and plastic collapse loads for un-reinforced mitred bends under pressure and bending

Min, Sung-Hwan,Jeon, Jun-Young,Lee, Kuk-Hee,Kim, Yun-Jae,Budden, Peter J. Elsevier 2011 The International journal of pressure vessels and Vol.88 No.11

<P><B>Abstract</B></P><P>Approximate limit and plastic collapse load solutions for un-reinforced mitred bends under internal pressure and under bending are proposed in this paper, based on three-dimensional finite element analysis and approximate solutions for smooth bends. Solutions are given for single- and multi-mitred bends (mainly for single and double segmented bends) with the pipe mean radius-to-thickness ratio (<I>r/t</I>) ranging from <I>r/t</I> = 5 to <I>r/t</I> = 50, and the bend radius-to-mean radius ratio (<I>R/r</I>) from <I>R/r</I> = 2 to <I>R/r</I> = 4. Internal pressure, in-plane bending and out-of-plane bending loads are considered, but not their combination. It is found that the essential features of limit and plastic collapse loads for mitred bends are similar to those for smooth bends, and thus existing solutions for smooth elbows can be used to construct limit loads and plastic collapse for mitred bends.</P> <P><B>Highlights</B></P><P>► This paper presents approximate limit/collapse load solutions for un-reinforced mitred bends. ► Internal pressure, in-plane bending and out-of-plane bending loads are considered. ► The essential features of limit/collapse loads for mitred bends are found to be similar to those for smooth bends. ► Existing limit/collapse load solutions for smooth elbows can be used for mitred bends.</P>

Fatigue analysis on the mooring chain of a spread moored FPSO considering the OPB and IPB

Kim, Yooil,Kim, Min-Suk,Park, Myong-Jin The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

The appropriate design of a mooring system to maintain the position of an offshore structure in deep sea under various environmental loads is important. Fatigue design of the mooring line considering OPB/IPB(out-of-plane bending/in-plane bending) became an essential factor after the incident of premature fatigue failure of the mooring chain due to OPB/IPB in the Girassol region in West Africa. In this study, mooring line fatigue analysis was performed considering the OPB/IPB of a spread moored FPSO in deep sea. The tension of the mooring line was derived by hydrodynamic analysis using the de-coupled analysis method. The floater motion time histories were calculated under the assumption that the mooring line behaves in quasi-static manner. Additional time domain analysis was carried out by prescribing the obtained motions on top of the selected critical mooring line, which was determined based on spectral fatigue analysis. In addition, nonlinear finite element analysis was performed considering the material nonlinearities, and both the interlink stiffness and stress concentration factors were derived. The fatigue damage to the chain surface was estimated by combining both the hydrodynamic and stress analysis results.

Fatigue analysis on the mooring chain of a spread moored FPSO considering the OPB and IPB

Yooil Kim,Min-Suk Kim,Myong-Jin Park 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

The appropriate design of a mooring system to maintain the position of an offshore structure in deep sea under various environmental loads is important. Fatigue design of the mooring line considering OPB/ IPB(out-of-plane bending/in-plane bending) became an essential factor after the incident of premature fatigue failure of the mooring chain due to OPB/IPB in the Girassol region in West Africa. In this study, mooring line fatigue analysis was performed considering the OPB/IPB of a spread moored FPSO in deep sea. The tension of the mooring line was derived by hydrodynamic analysis using the de-coupled analysis method. The floater motion time histories were calculated under the assumption that the mooring line behaves in quasi-static manner. Additional time domain analysis was carried out by prescribing the obtained motions on top of the selected critical mooring line, which was determined based on spectral fatigue analysis. In addition, nonlinear finite element analysis was performed considering the material nonlinearities, and both the interlink stiffness and stress concentration factors were derived. The fatigue damage to the chain surface was estimated by combining both the hydrodynamic and stress analysis results.

Theoretical Analysis of Bending Stresses to Design a Sprocket for Transportation Part of a Chinese Cabbage Collector

이예슬,ALI MOHAMMOD,Md Nafiul Islam,Kamal Rasool,장보은,Md Shaha Nur Kabir,강태경,정선옥 한국농업기계학회 2020 바이오시스템공학 Vol.45 No.2

Purpose Force calculation, stress, and fatigue analysis are major issues in machine design to ensure the life expectancy of sprocket-gear power transmission systems. Therefore, this study aims to conduct a theoretical analysis of bending stresses to select the size and component materials for the power transmission part of a Chinese cabbage collector that is under development. Methods The three-dimensional models of a 14T sprocket gear for two steel materials, SCr420H and SM45C, were generated, employing commercial software. The bending stresses, deformations, and fatigue damages of the designed sprocket were determined by varying the face width and pressure angle of the sprocket teeth. The Lewis and American Gear Manufacturer Association (AGMA) equations were used to calculate the bending stresses. The calculated bending-stress values were compared with the stress values obtained from finite-element analysis (FEA). Results The maximum stress values on the gear teeth were 650.07, 826.23, and 840.77 MPa for a 20° pressure angle by using the Lewis, AGMA, and FEA methods, respectively. The simulated maximum stress value was higher than the yield strength of the SM45C steel and lower than the yield strength of the SCr420H steel. In addition, the maximum face width showed the minimum bending stress and fatigue damage for the selected material. Hence, considering the safety factor, the steel material SCr420H was selected with a 4.5-mm face width for designing the power transmission part of the Chinese cabbage collector. Conclusion The analysis of bending stresses presented in this research can guide the design of a sprocket for the efficient transfer of Chinese cabbages using the proposed Chinese cabbage collector.

Fatigue Analysis for Automotive Wheel Bearing Flanges

Ji-Won Jin,Ki Weon Kang,Seungpyo Lee 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.4

The automotive wheel bearing is an integral component of automobiles that transfers rotation and supports the weight of the vehicle. The life of automotive wheel bearings can be categorized into the raceway and flange lives. The raceway life is based on the spalling that occurs in the raceway and can be determined analytically using the basic rating life calculation method for the rolling bearing. The flange life is based on failure involving the flange and can be numerically predicted through fatigue analysis. In particular, the fatigue analysis for predicting the flange life must consider rotation owing to the bearing characteristics, unlike the general fatigue analysis. In this study, we examined the fatigue analysis of the automotive wheel bearing flange while considering rotation. We performed sequential stress and fatigue analyses using commercial software. As the fatigue material properties are required for fatigue analysis, we obtained the properties by conducting a rotary bending fatigue test on the bearing materials. To verify the results of the analysis, we compared the analysis results with the test results. The validity of the proposed fatigue analysis was confirmed.

Development of Integrated Whipping Analysis Program Using 1-D Beam Analogy Model

Jeong-il Kwon,Jung-hoon Chung,Yun-ho Shin,Jin-Hyeong Kim,Tae-Muk Choi 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5

Whipping response analysis for a naval surface ship caused by UNDEX(UNDerwater EXplosion) bubble pulse should be carried out for the evaluation of longitudinal hull-girder strength. For this evaluation, 1-D beam analogy analysis and 3-D analysis using the finite element method are typically used during the ship design process. But these analytic calculation processes are very complicated in order to compare and estimate the calculated UNDEX whipping moments with the allowable bending moment of a given design which can be derived from the allowable strength criteria of longitudinal hull girder structural members. In this paper, to decrease these complicated flipping analysis process and promote the calculation efficiency, an integated whipping analysis program has been developed based on the thin-walled Timoshenko beam theory and the modal analysis method using wetted1 vertical vibratory modes of the hull-girder. This program is developed for the efficiency of UNDEX whipping analysis process based on best practices including to effectively manage, utilize and evaluate the massive and various simulation data and results including UNDEX scenarios and ship design data. Finally, the usefulness of the developed program has been confirmed with the comparison of results obtained by between 1-D and 3-D analysis.