• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.630-633
• /
• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and BGA solder joint s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. A model based on plastic-strain rate such as the Coffin-Manson Fatigue Model is utilized in this study. The effects of random variables such as frequency, maximum temperature, and temperature variations on the failure probability of the BGA solder joint are systematically investigated by using a failure probability model with the first order reliability method(FORM).

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.365-370
• /
• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and solder joint' failure. The first order Taylor series expansion of the limit state function incorporating with Tresca failure criterion is used in order to estimate the failure probability of solder joints under heated condition. Using shear stresses and shear strains appeared on the solder joint, we estimate the failure probability of solder joints with the Tresca failure criterion. The effects of random variables such as CTE, distance of the solder joint from the neutral point(DNP), temperature variation and height of solder on the failure probability of the solder joint are systematically studied by using the failure probability model with first order reliability method(FORM).

• Earthquakes and Structures
• /
• v.11 no.5
• /
• pp.905-924
• /
• 2016

Several two-dimensional analytical beam column joint models with varying complexities have been proposed in quantifying joint flexibility during seismic vulnerability assessment of non-ductile reinforced concrete (RC) frames. Notable models are the single component rotational spring element and the super element joint model that can effectively capture the governing inelastic mechanisms under severe ground motions. Even though both models have been extensively calibrated and verified using quasi-static test of joint sub-assemblages, a comparative study of the inelastic seismic responses under nonlinear time history analysis (NTHA) of RC frames has not been thoroughly evaluated. This study employs three hypothetical case study RC frames subjected to increasing ground motion intensities to study their inherent variations. Results indicate that the super element joint model overestimates the transient drift ratio at the first story and becomes highly un-conservative by under-predicting the drift ratios at the roof level when compared to the single-component model and the conventional rigid joint assumption. In addition, between these story levels, a decline in the drift ratios is observed as the story level increased. However, from this limited study, there is no consistent evidence to suggest that care should be taken in selecting either a single or multi component joint model for seismic risk assessment of buildings when a global demand measure such as maximum inter-storey drift is employed in the seismic assessment framework.

• Steel and Composite Structures
• /
• v.6 no.1
• /
• pp.33-53
• /
• 2006

The rotational behaviour of bolted extended end plate beam-to-column connections is evaluated in the context of the component method. The full moment-rotation response is characterized from the force-deformation curve of the individual joint components. The deformability of end plate connections is mostly governed by the bending of the column flange and/or end plate and tension elongation of the bolts. These components form the tension zone of the joint that can be modelled by means of "equivalent T-stubs". A systematic analytical procedure for characterization of the monotonic force-deformation behaviour of individual T-stub connections is proposed. In the framework of the component method, the T-stub is then inserted in the joint spring model to generate the moment-rotation response of the joint. The procedures are validated with the results from an experimental investigation of eight statically loaded extended end plate bolted moment connections carried out at the Delft University of Technology. Because ductility is such an important property in terms of joint performance, particularly in the partial strength joint scenario, special attention is given to this issue.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.243-250
• /
• 2004

This paper reports on the evaluation of the initial stiffness of steel joints using component method as well as experimental tests. The so-called component method corresponds precisely to a simplified mechanical model composed of extensional springs and rigid links, whereby the joint is simulated by an appropriate choice of rigid and flexible components. An application to a cantilever beam-to-column steel joint is presented and compared to the experimental results obtained under cyclic loading condition. Comparison between numerical and experimental results allows to conclude that the numerical model is able to simulate, with a good level of accuracy for initial stiffness, the behaviour of beam-to-column joints.

• Steel and Composite Structures
• /
• v.20 no.3
• /
• pp.469-486
• /
• 2016

Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics ($M-{\phi}$ relationship), or at least three basic joint properties, namely the moment resistance $M_R$, the rotational stiffness $S_j$ and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance $M_R$, initial stiffness $S_{j.ini}$ and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2005.11a
• /
• pp.129-132
• /
• 2005

Recently, Domestic construction industry is confronted with a new phase by increasement of stock and elation of the concern about environment. In particular, the focus on remodeling as an altanative of the reconstruction system that squanders resources and creates massive construction waste, has increased. However, current remodeling methods are being obstructed factor, because design has not considered the remodeling at the beginning of the construction. The purpose of this study is to search for the improvement of component joint for efficient remodeling. Field survey is conducted on the components grouped by spaces(living room/bed room/kitchen/bathroom) of unit living at 6 construction sites in Seoul & countries. As a result, total 228 component joints are selected and classified according to interface condition and problem pattern.

• PNF and Movement
• /
• v.7 no.4
• /
• pp.17-23
• /
• 2009

Purpose : The objective of this study was conducted to find out treatment of weight bearing joint problems. Method : This is a literature study with books, seminar note and international PNF course books. Result : In joint therapy have to consider that what kind joint mechanics during movement, what kind relation between rotatory component of the force and translatory component of the force, what kind muscles are in the global mobilizer(GM) and local stabilizer(LS). One joint has muscle imbalance between GM and LS. It will make joint surface degenerative change which will make joint pain. Conclusion : Joint therapy is not only joint mobilization but also biomechanics of joint and GM's and LS's role. Total knee of hip joint replacement is not perfect. Before surgery have to be find out problem solving method within the physical medicine.

• The Academic Congress of Korean Shoulder and Elbow Society
• /
• 2004.11a
• /
• pp.129-135
• /
• 2004

만약 Glenoid side를 해부학적으로 정확하게 치환하고, 상완골측의 prosthesis를 삽입할 때 실제 골두의 크기와 같은 prosthetic head를 쓰고, humeral stem의 위치 및 높이를 정확하게 맞추어 삽입하여, humeral head component의 center와 glenoid component의 center가 일치되고 lateral glenohumeral offset이 정상에 가깝게 수술을 시행하면 인공 치환물로 대치된 glenohumeral joint가 정상에 가장 가까운 kinematics를 가질 수 있다 (당연한 얘기지만 이렇게 수술하려면 많은 경험이 필요). 따라서 Glenohumeral joint의 인공 관절 치환술은 항상 technique-dependant 수술이며, 아무리 좋은 치환물도 훌륭한 수술 기법보다 더 중요할 수는 없다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.35 no.6
• /
• pp.343-349
• /
• 2022

This paper proposes a new topology optimization scheme to determine optimized joints for multi-component models. The joints are modeled as zero-length high-stiffness spring elements. The spring joints are considered as mesh-independent springs based on a joint-element interpolation scheme. This enables the changing of the location of the joints regardless of the connected nodes during optimization. Because the joints are movable, the locations of the optimized joints should be aggregated at several points. In this paper, the novel joint dispersal (JD) constraint to prevent joint clustering is proposed. With the joint dispersal constraint, it is possible to determine the optimized joint location as well as optimized topologies while maintaining the minimum distance between each joint. The mechanical compliance value is considered as the objective function. Several topology optimization examples are solved to demonstrate the effect of the joint dispersal constraint.