• Computers and Concrete
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• v.5 no.3
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• pp.261-277
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• 2008

This paper presents methodologies for remaining life prediction of plain concrete structural components considering tension softening effect. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. A methodology to account for tension softening effects in the computation of SIF and remaining life prediction of concrete structural components has been presented. The tension softening effects has been represented by using any one of the models mentioned above. Numerical studies have been conducted on three point bending concrete structural component under constant amplitude loading. Remaining life has been predicted for different loading cases and for various tension softening models. The predicted values have been compared with the corresponding experimental observations. It is observed that the predicted life using bi-linear model and power curve model is in close agreement with the experimental values. Parametric studies on remaining life prediction have also been conducted by using modified bilinear model. A suitable value for constant of modified bilinear model is suggested based on parametric studies.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.178-201
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• 2019

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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.57-65
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• 2022

This study investigated the electromechanical response of smart ultra-high performance fiber reinforced concretes (S-UHPFRCs) under flexural loading to evaluate the self-sensing capacity of S-UHPFRCs in both tension and compression region. The electrical resistivity of S-UHPFRCs under flexural continuously changed even after first cracking due to the deflection-hardening behavior of S-UHPFRCs with the appearance of multiple microcracks. As the equivalent bending stress increased, the electrical resistivity of S-UHPFRCs decreased from 976.57 to 514.05 kΩ(47.0%) as the equivalent bending stress increased in compression region, and that did from 979.61 to 682.28 kΩ(30.4%) in tension region. The stress sensitivity coefficient of S-UHPFRCs in compression and tension region was 1.709 and 1.098 %/MPa, respectively. And, the deflection sensitivity coefficient of S-UHPFRCs in compression region(30.06 %/mm) was higher than that in tension region(19.72 %/mm). The initial deflection sensing capacity of S-UHPFRCs was almost 50% of each deflection sensitivity coefficient, and it was confirmed that it has an excellent sensing capacity for the initial deflection. Although both stress- and deflection-sensing capacity of S-UHPFRCs under flexural were higher in compression region than in tension region, S-UHPFRCs are sufficient as a self-sensing material to be applied to the construction field.

• Steel and Composite Structures
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• v.47 no.2
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• pp.289-296
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• 2023

The failure of a thin-walled tube was studied in this paper based on three failure models. Both proportional and non-proportional loading paths were applied. Proportional loading consisted of combined tension-torsion. Cyclic non-proportional loading was also applied. It was a circular out-of-phase axial-shear stress loading path. The third loading path was a combination of a constant internal pressure and a bending moment. The failure models under study were equivalent plastic strain, modified Mohr-Coulomb (Bai-Wierzbicki) and Tearing parameter models. The elasto-plastic analysis was conducted using J2 criterion and nonlinear kinematic hardening. The return mapping algorithm was employed to numerically solve the plastic flow relations. The effects of the hydrostatic stress on the plastic flow and the stress triaxiality parameter on the failure were discussed. Each failure model under study was utilized to predict failure. The failure loads obtained from each model were compared with each other. The equivalent plastic strain model was independent from the stress triaxiality parameter, and it predicted the highest failure load in the bending problem. The modified Mohr-Coulomb failure model predicted the lowest failure load for the range of the stress triaxiality parameter and Lode's angle.

• Structural Engineering and Mechanics
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• v.24 no.2
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• pp.227-245
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• 2006

The performance of a three dimensional non-linear finite element model for hyperelastic material considering the effect of compressibility is studied by analyzing rubber blocks under different modes of deformation. It includes simple tension, pure shear, simple shear, pure bending and a mixed mode combining compression, shear and bending. The compressibility of the hyperelastic material is represented in the strain energy function. The nonlinear formulation is based on updated Lagrangian (UL) technique. The displacement model is implemented with a twenty node brick element having u, ${\nu}$ and w as the degrees of freedom at each node. The results obtained by the present numerical model are compared with the analytical solutions available for the basic modes of deformation where the agreement between the results is found to be satisfactory. In this context some new results are generated for future references since the number of available results on the present problem is not sufficient enough.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.903-905
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• 2003

High temperature superconductor (HTS) tapes are now commercially available for practical applications to apply various purposes. However HTS tapes show different electrical and mechanical characteristics, according to the manufacturers who are trying to apply various fabrication processes and treatments. From the viewpoint of an application it is very important to investigate the properties of HTS tapes under mechanical stress because the tapes will be wound with twisting and tension in applications such as magnets and cables. Thus, we studied characteristics of HTS tapes and measure critical current under bending, considering of a mechanical conditions. A description of some typical results will be presented with discussions.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.432-437
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• 2007

Sidewall curl is the curvature that results from non-uniform through-thickness strain present in the sheet stamping process which involves material flow over a die radius. In order to understand and control sidewall curl for tight fit-up tolerances, an analytical model that can provide a reliable measure for the amount of curl would be very helpful. In this study, a model is developed based on the moment-curvature relationship during bending-under-tension operations. The analytical model includes the variables of applied tensile force, the yield strength, the elastic modulus, the bending radius, and the sheet thickness, which are the primary factors affecting sidewall curl during sheet stamping operations. For the accuracy of analytical model, six possible deformation patterns are proposed on the basis of material properties and bending geometries.

• Progress in Superconductivity and Cryogenics
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• v.9 no.4
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• pp.11-15
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• 2007

In practical applications of HTS tapes for electric devices such as coils and power cables, the jointing of HTS tapes is inevitable even though long length tapes have recently been achieved. The critical current, $I_c$, degradation behaviors with tensile and bending deformations were investigated in commercially available YBCO coated conductor tapes. When the V-I relationship was measured at the jointed section of the lap-jointed YBCO CC tapes, the resistance at the joint decreased with increasing joint length. The critical load for 95% $I_c$ retention were determined for the IBAD and RABiTS YBCO tapes and they were 175 and 355N, respectively. Fracture occurred at the unjointed part which represents strong copper lamination and solder jointing. The electro-mechanical properties of lap-jointed CC tapes depended on the properties of single tapes. The V-I behavior under bending strain was similar with the tensile case.

• Computers and Concrete
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• v.17 no.1
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• pp.29-51
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• 2016

Tension-stiffening is the contribution of concrete between the cracks to carry tensile stresses after cracking in Reinforced Concrete (RC) members. In this paper, a tension-stiffening model has been proposed for computationally efficient nonlinear analysis of RC flexural members subjected to service load. The proposed model has been embedded in a typical cracked span length beam element. The element is visualized to consist of at the most five zones (cracked or uncracked). Closed form expressions for flexibility and stiffness coefficients and end displacements have been obtained for the cracked span length beam element. Further, for use in everyday design, a hybrid analytical-numerical procedure has been developed for nonlinear analysis of RC flexural members using the proposed tension-stiffening model. The procedure yields deflections as well as redistributed bending moments. The proposed model (and developed procedure) has been validated by the comparison with experimental results reported elsewhere and also by comparison with the Finite Element Method (FEM) results. The procedure would lead to drastic reduction in computational time in case of large RC structures.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.58-58
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• 2010

The purpose of this study is to evaluate the structural safety at the topside weldment of hull structure, which was welded after launching. For it, the variations of residual stress and distortion at the topside weldment with loading conditions such as hull girder hogging bending moment after launching and free initial loading state was evaluated by using FEA. And the maximum stress range at the weldment under design loads specified by classification society was evaluated by FEA. In this case, the residual stress and welding distortion at the topside weldment was assumed to be initial imperfection. In accordance with FEA results, regardless of initial loading condition, tensile residual stress was found. However, the residual stress and welding distortion at the topside weldment produced under hogging condition was less than those of topside weldment under free loading state. That is, the amount of residual stress at the topside weldment decreased with an increase in the amount of tension load caused by hogging condition. It was because the compressive thermal strain at the topside weldment produced during welding was reduced by tensile load. However, the maximum stress range at the topside weldment under maximum hull girder bending moment was almost similar regardless of initial loading condition. So, if the problem related to the soundness of weldment is not introduced by initial load, the effect of initial loading condition during welding on fatigue strength of topside weldment could be negligible.