• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.307-312
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• 2012

This study aims to investigate the effect of the post weld treatments on the fatigue life of T-type welded structure made by a SM50A steel material, generally used for excavators, because changes in the geometry, material and surface properties of welded regions affect the fatigue life of welded structures. T-type test specimens were prepared by the CO2 welding of rolled steel plates (SM50A steel) with a thickness of 10 mm at a welding speed of 30 cm/min and these Ttype welded specimens were further treated by UIT (Ultrasonic Impact Treatment) and/or toegrinding post welding treatment methods. In order to investigate improvements on the fatigue life of the samples. 3-point bending fatigue tests were conducted with a stress ratio of R=0.1 under a cyclic loading environment at a frequency of 5 Hz, via a hydraulic fatigue testing machine (${\pm}100\;kN$, MTS 809). The tests were performed at room temperature. The fatigue life of UIT specimens was approximately 25 times longer than that of as-welded specimens at a stress amplitude of 281 MPa, while toe-grinding specimens exhibited 4.15 times longer fatigue life. The current results could provide important guidelines to determine the proper post weld treatment methodologies of T-type welded parts for excavators with a satisfactory fatigue life although under severe operating conditions.

• Journal of Korean Association for Spatial Structures
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• v.12 no.2
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• pp.45-53
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• 2012

This paper derives Isogeometric analysis and post-processing method of surface that are generated by NURBS basis function for accurate geometric modeling and structure analysis of free-form. By deforming these parameters that are consisted of control points, knots, polynomial, variable geometric models are derived. The basis function that is used to Isogeometric analysis is same to the basis function of NURBS that is used to generate geometric models. For performing isogeometric analysis, h-p-k refinement is performed without changing of original geometry. To visualize the results of isogeometric analysis that control points' displacements, post-processing method that is the interface method between IGES format and Rhinoceros is derived.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.451-462
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• 2023

Lumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre-localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post-localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber-reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.4
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• pp.57-66
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• 1989

In this paper, a theory for the static analysis of large plastic deformations of 3-dimensional frames, aiming at application to the collapse analysis of ship structures, is presented. In the frame analysis formulation, effects of shear deformations are included. A plastic hinge is inserted into the field of a beam end, and post. failure deformation of the plastic hinge is characterized by finite rotations and extensions. In order to model deep web frames of ship's structures into a framed structures, collapse of thin-walled plate girders is investigated. The proposed analysis method is applied to several ship structural models in the references.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.263-267
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• 1995

The usual methods for the temperature control of mass-concrete structures include the use of low-heat cement, pre-cooling, post-cooling, or sheet curing. In order to control the heat of hydration during the construction of mass-concrete structures, the combination of the above methods is commonly employed. For the construction of mass-concrete structures such as massive pier or anchor, it is necessary to control the curing temperature with pipe cooling. In this study, the method of analysis on the effect of pipe of was proposed to prevent the thermal cracking due to heat of hydration In addition the effect of covering the concrete surface with blanket insulation was investigated. The results of the present study may be useful for the prediction of curing temperature of mass-concrete structures and the reasonable construction management.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3068-3078
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• 1996

stereolithography is a process used to rapidly produce polymer components directly from a computer representation of the part. There are several considerations to be made for the efficient use of the process. Especially, the necessity of support structures, which prevent the part from warping, sagging, or parachuting and toppling as the elevator moves up and down in the resin, is one concern. After solidification, the support structures must by removed in the end. Bacause this post-treatment process is often performed manually, the more the support structures, the more it increases the finishing operations. Especially for a complicated part, the removal operations may be difficult, take so much time, and even reduce the accuracy of the product. Thus it is important to efficiently generate the efficient support structure for each part geometry. This paper proposes a procedure to automatically generate the supprot structures focused on accuracy, efficiency, convenience, and generation speed.

• Structural Engineering and Mechanics
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• v.9 no.2
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• pp.111-126
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• 2000

Truss type structures are attractive to a variety of engineering applications on earth as well as in space due to their high stiffness to mass ratios and ease of construction and fabrication. During the service life, an individual member of a truss structure may lose load carrying capacity due to many reasons, which may lead to collapse of the structure. An analytical and computational procedure has been developed to study the response of truss structures subject to member failure under static and dynamic loadings. Emphasis is given to the dynamic effects of member failure and the propagation of local damage to other parts of the structure. The methodology developed is based on nonlinear finite element analysis technique and considers elasto-plastic material nonlinearity, postbuckling of members, and large deformation geometric nonlinearity. The pseudo force approach is used to represent the member failure. Results obtained for a planar nine-bay indeterminate truss undergoing sequential member failure show that failure of one member can initiate failure of several members in the structure.

• Steel and Composite Structures
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• v.5 no.6
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• pp.515-533
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• 2005

Buckling and post-buckling of cold-formed steel members are rather difficult to predict due to material and geometrical non-linearity. However, numerical techniques have reached a level of maturity such that many are now successfully undertaking ultimate strength analysis of cold-formed steel members. In numerical non-linear analysis, both geometrical and material imperfections, have to be estimated and properly used. They must be codified in terms of shape and magnitude. The presented paper represents a state-of-art report, including relevant results obtained by the authors and collected from literature, on that problem.

• Earthquakes and Structures
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• v.8 no.3
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• pp.541-553
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• 2015

Structural Health Monitoring (SHM) systems can provide valuable information regarding the safety of structures during and after ground motions which can be used by authorities to reduce post-earthquake hazards. Strain gages as a key element play an important role in the success of SHM systems. Reducing the number of required strain gages while keeping the efficiency of SHM system not only can reduce the cost of structural health monitoring but also avoids storage and process of uninformative data. In this study, a method based on performance based seismic design of structures is proposed for ideal placement of stain gages in structures. The robustness and efficiency of the proposed method is demonstrated through installation of strain gages on an Airport Traffic Control (ATC) Tower. The obtained results show that the number of required strain gages decrease significantly.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.403-413
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• 2017

Residual axial capacity from numerical analysis was widely used as a critical indicator for damage assessment of reinforced concrete (RC) columns subjected to blast loads. However, the convergence of the numerical result was generally based on the displacement response, which might not necessarily generate the correct post-blast results in case that the strain softening behavior of concrete was considered. In this paper, two widely used concrete models are adopted for post-blast analysis of a RC column under blast loading, while the calculated results show a pathological mesh size dependence even though the displacement response is converged. As a consequence, a nonlocal integral formulation is implemented in a concrete damage model to ensure mesh size independent objectivity of the local and global responses. Two numerical examples, one to a RC column with strain softening response and the other one to a RC column with post-blast response, are conducted by the nonlocal damage model, and the results indicate that both the two cases obtain objective response in the post-peak stage.