• Bulletin of the Society of Naval Architects of Korea
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• 제26권4호
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• pp.81-93
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• 1989

The present study attempts to develop the theoretical model for the damage estimation of offshore tubular members which are subjected to the accidental impact loads due to collision, falling objects and so on. For the reasons of the simplicity of the problem being considered, however, this paper postulates that the accidental load can be approximated to be the quasi-static one, in which dynamic effects are negelcted. Based upon the theoretical and experimental results which are obtained from the present study as well as the existing literature, the load-displacement relations taking the interaction effect between the local denting and the global bending deformation into account are presented in the explicit form when the concentrated lateral load acts on the tubular member whose end condition is supposed to be rotation ally free and axially restrained, in which membrane forces develop. Thus, the practical estimation of damage deformation for the local denting and the global bending damage of tubular members against the accidental loads is possible and also the collision absorption capability of the member can be calculated by performing the integration of the area below the given load-displacement curves, provided that all the energy is dissipated to the deforming the member itself.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제30권6A호
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• pp.513-523
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• 2010

For continuous I-girder bridges, a large negative bending moment is generated near pier region so that plastic hinge is first formed at this point. Then, the bending moment is redistributed when the I-girder has enough flexural ductility (or rotational capacity). However, for I-girder with high strength steel, it is known that the flexural ductility is considerably decreased by increasing the yield strength of material. Thus, it is necessary to conduct a study for guaranteeing proper flexural ductility of I-girder with high-strength steel. In this study, the evaluation of flexural ductility of negative moment region of I-girder with high strength steel where yield stress of steel is 680 MPa is presented based on the results of finite element analysis and experiment. From the results, it is found that the flexural ductility of the I-girder is significantly reduced due to the increase of elastic deformation and the decrease of plastic deformation ability of the material when the yield strength increases. In this study, the method to improve the flexural ductility of I-girder with high strength steel is proposed by an unequal installation of cross beam and an optimal position of cross beam is also suggested. Finally, the effects of the unequal installation of cross beam on the flexural ductility are discussed based on the experimental results.

• Journal of the Society of Disaster Information
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• 제20권2호
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• pp.329-338
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• 2024

Purpose: This study verified the safety of the improved box-type girder behavior by comparing and evaluating the bending behavior results of a full-scale specimen based on the analytical behavior of the splice element PSC U-shaped girder with integrated tensioning systems. Method: Based on the results of the service and strength limit state design using the bridge design standard(limit state design method), the applied load of a 40m full-scale specimen was calculated and a static loading experiment using the four-point loading method was performed. Result: When the design load, crack load, and ultimate load were applied, the specimen deflection occurred at 97.1%, 98.5%, and 79.0% of the analytical deflection value. When the design load, crack load, and ultimate load were applied, the crack gauge was measured at 0.009~0.035mm, 0.014~0.050mm, and 6.383~5.522mm at each connection. Conclusion: The specimen behaved linear-elastically until the crack load was applied, and after cracks occurred, it showed strainhardening up to the ultimate load, and it was confirmed that the resistance of bending behavior was clearly displayed against the applied load. The cracks in the dry joints were less than 25% of grade B based on the evaluation of facility condition standard. The final residual deformation after removing the ultimate load was 0.114mm, confirming the stable behavior of the segment connection.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제37권4호
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• pp.259-265
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• 2024

Shape memory alloy (SMA)-textile actuators have attracted significant attention across various fields, including soft robotics and wearable technology. These smooth actuators are developed by combining SMA and simple textile fibers and then knitting them into two loop patterns known as the knit (K-loop) and plain (P-loop) patterns. Both loops are distinguished by opposite bending characteristics owing to loop head geometry. However, the knitting processes for these actuator sheets require expertise and time, resulting in high production costs for knitted loop actuation sheets. This study introduces a novel method by which to assess the strain in SMA textile-based actuators, which experience large deformations when subjected to voltage. Owing to the highly nonlinear constitutive equations of the SMA material, developing an analytical model for numerical analysis is challenging. Therefore, this study employs a novel approach that utilizes a linear constitutive equation to analyze large deformations in SMA material with nonlinear geometry considerations. The user-defined material (UMAT) subroutine integrates the linear constitutive equation into the ABAQUS software suite. This equivalent unit cell (EUC) model is validated by comparing the experimental bending actuation results of K-loops and P-loops.

• Journal of the Microelectronics and Packaging Society
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• 제18권2호
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• pp.17-27
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• 2011

This paper describes an experimental study and finite element analysis (FEA) carried out for investigating thermal deformation behavior of solders, resulting from temperature change in the solder. With such a goal in mind, a shear specimen that was composed of two metal bars having different coefficient of thermal expansion and solder blocks placed between two bars was designed and fabricated. Two different types of solder blocks, eutectic solder (Sn/36Pb/ 2Ag) and lead-free solder (Sn/3.0Ag/0.5Cu) were tested as well. Fringe patterns for several temperature steps were recorded and analyzed for three temperature cycles using a real-time moir$\acute{e}$ setup. The experimental data was verified with FEA and used to evaluate the suitability for numerous solder constitutive models available in literatures. FEA employing Anand material model suggested by Darveaux et al. and Chang et al. were found to be in an excellent agreement with the experimental results for the eutectic solder and the lead-free solder, respectively. In addition, numerical predictions on bending displacement, shear strain and viscoplastic distortion energy are documented and viscoplastic deformation behavior of two types of solder material are compared.

• Journal of Korean Society of Steel Construction
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• 제21권6호
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• pp.597-608
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• 2009

In this paper, large-deformation elasto-plastic analysis of space frames that considersjoint connection properties is presented. This method is based on the large-deformation formula with finite rotation, which was developed initially for elastic systems, and is extended herein to include the elasto-plastic effect and the member joint connection properties of semi-rigid what?. The analytical method was derived from the Eulerian concept, which takes into consideration the effects of large joint translations and rotations. The localmember force-deformation relationships were obtained from the beam-column approach, and the change caused by the axial strain in the member chord lengths and flexural bowing were taken into account. The effect of the axial force of the member on bending and torsional stiffness, and on the plastic moment capacity, is included in the analysis. The material is assumed to be ideally elasto-plastic, and yielding is considered concentrated at the member ends in the form of plastic hinges. The semi-rigid properties of the member joint connection are considered based on the power or linear model. The arc length method is usedto trace the post-buckling range of the elastic and elasto-plastic problems with the semi-rigid connection. A sample non-linear buckling analysis was carried out with the proposed space frame formulations to demonstrate the potential of the developed method in terms of its accuracy and efficiency.

• Journal of the Korea institute for structural maintenance and inspection
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• 제22권6호
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• pp.170-175
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• 2018

For the seismic performance, it is necessary to prevent the destruction of the expansion joint device due to the appropriate deformation of the expansion joint device due to the seismic force. Recently, the hinge is installed on the fingering of the expansion joint device in Korea, New products are being developed. In this paper, we have experimentally evaluated the real scale resistance of the expansion joints with rotational finger joints against load at right angle to the bridge axis. Experimental results show that the maximum horizontal displacement is about 21.1mm for conventional stretch joints and 51.00mm for seismic stretch joints. It is presumed that the existing expansion joint test specimen is resistant to the load in a direction perpendicular to the throat axis, and then the bending and shear deformation of the finger are excessively generated and the fracture phenomenon is likely to occur. On the other hand, in the case of the seismic expansion joint, the deformation of the load due to the load is absorbed by the hinge of the finger with respect to the load in the direction perpendicular to the throat, so that only horizontal deformation in the direction of load action.

• Journal of the Korean Geotechnical Society
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• 제26권6호
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• pp.57-70
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• 2010

Recent earthquakes have demonstrated that the tunnels, which were once considered to be highly resistant to earthquakes, are susceptible to substantial damage under severe seismic loading. Among various modes of deformation under an earthquake loading, the response of the tunnel in the transverse direction is known to be the critical mode. This paper investigates the seismic response of the tunnel in the transverse direction using the method of seismic displacement, which is a type of pseudo-static analysis. Firstly, the methods of calculating the ground deformation are compared. It is shown that the single and double cosine may not provide an accurate estimation of the ground deformation, and that a one-dimensional site response analysis needs to be performed for a more reliable evaluation. Secondly, the tunnel responses are calculated using the simplified, analytical, and numerical solutions. It is demonstrated that the simplified method provides poor estimates of the tunnel response ground deformation. The analytical solution is shown to be effective in modeling circular tunnels in uniform ground, but has serious limitation in modeling tunnel response in non-uniform ground. Numerical analyses are shown to be applicable to all cases, and give the most accurate estimates of the tunnel response. It is also demonstrated that the linear solutions can be so conservative that the soil nonlinearity needs to be accounted for more accurate evaluation of the tunnel response.

• Journal of Korean Society of Steel Construction
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• 제16권3호통권70호
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• pp.295-303
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• 2004

In this paper, an improved four-node Reissner-Mindlin plate-bending element with enhanced assumed strain field is presented for the analysis of isotropic and laminated composite plates. To avoid the shear locking and spurious zero energy modes, the transverse shear behavior is improved by the addition of a new enhanced shear strain based on the incompatible displacement mode approach and bubble function. The "standard" enhanced strain fields (Andelfinger and Ramm, 1993) are also employed to improve the in-plane behaviors of the plate elements. The four-node quadrilateral element derived using the first-order shear deformation theory is designated as "14EASP". Several applications are investigated to assess the features and the performances of the proposed element. The results are compared with other finite element solutions and analytical solutions. Numerical examples show that the element is stable, invariant, passes the patch test, and yields good results especially in highly distorted regimes.

• Journal of the Korean Academy of Esthetic Dentistry
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• 제3권1호
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• pp.32-43
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• 1995

Ni-Ti alloy has excellent corrosion resistance, biocompatibility, shape memory effect and superelasticity, so it has been used widely in biomedical fields. But it has difficulty in casting due to its high melting temperature and oxygen affinity at high temperature. Recently it has been attempted to cast Ni-Ti alloy using new casting machine and investment. The purpose of this study was to examine the superelastic behavior of cast shape memory Ni-Ti alloy and to compare the mechanical properties of the cast shape memory alloy with those of commercial alloys for removable partial denture framework. Ni-Ti alloy(Ni 50.25%, Ti 49.75% : atomic ratio) was cast with dental argon-arc pressure casting machine and Type IV gold alloy, Co-Cr alloy, Ni-Cr alloy, pure titanium were cast as reference. Experimental cast Ni-Ti alloy was treated with heat($500{\pm}2^{\circ}C$) in muffle furnace for 1 hour. Transformation temperature range of cast Ni-Ti alloy was measured with differential scanning calorimetry. The superelastic behavior and mechanical properties of cat Ni-Ti alloy were observed and evaluated by three point bending test, ultimate tensile test, Vickers microhardness test and scanning electron microscope. The results were as follows : 1. Cast Ni-Ti alloy(Ni 50.25%, Ti 49.75% : atomic ratio) was found to have superelastic behavior. 2. Stiffness of cast Ni-Ti alloy was considerably lesser than that of commercial alloys for removable partial denture. 3. Permanent deformation was observed in commercial alloys for removable partial denture framework at three point bending test over proportional limit(1.5mm deflection), but was not nearly observed in cast Ni-Ti alloy. 4. On the mechanical properties of ultimate tensile strength, elongation and Vickers microhardness number, cast Ni-Ti alloy was similiar to Type IV gold alloy, Co-Cr alloy, Ni-Cr alloy and pure titanium. With these results, cast Ni-Ti alloy had superelastic behavior and low stiffness. Therefore, it is suggested that cast Ni-Ti alloy may be applicated to base metal alloy for removable partial denture framework.