• Journal of the Korean GEO-environmental Society
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• v.16 no.10
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• pp.15-22
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• 2015

In this study, to evaluate the long-term behavior characteristics and the loss of prestress force, the long-term measurement of the tensile anchors in the actual construction was performed and the results were analyzed comparing with the existing estimation. As the reinforcement member used for the purpose of slope stability or uplift-resisting of the permanent structure, etc, the permanent anchor should maintain the functions during the performance period of the structure differently from the temporary anchor. However, as the time passes by, since the relaxation and the creep of the anchor occur constantly, the management for the loss of tensile force is essential to perform the functions stably. So far, the loss of the tensile force has been estimated according to the reduction of the prestress using elasticity theory and using the relaxation value according to the type of tension member and the test using the long-term measurement is limited. Therefore, in this study, the site condition and the ground were investigated for the tensile anchor in the actual construction and the long-term measurement results more than 500 days was analyzed by installing the loadcell, inclinometer and the groundwater level gauge. In addition, the long-term behavior characteristics were evaluated by comparing the disposition of the measured earth retaining wall and the tension force loss of the anchor with the existing interpretation results. In the evaluation results, the most of the tension force loss occurs within 90 days and the loss was measured less than the estimated values.

• Journal of the Korea Society of Computer and Information
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• v.23 no.11
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• pp.43-49
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• 2018

In this paper, we propose a displacement measurement method based on deep learning using image data obtained from tensile tests of a material specimen. We focus on the fact that the sequential images during the tension are generated and the displacement of the specimen is represented in the image data. So, we designed sample generation model which makes sequential images of specimen. The behavior of generated images are similar to the real specimen images under tensile force. Using generated images, we trained and validated our model. In the deep neural network, sequential images are assigned to a multi-channel input to train the network. The multi-channel images are composed of sequential images obtained along the time domain. As a result, the neural network learns the temporal information as the images express the correlation with each other along the time domain. In order to verify the proposed method, we conducted experiments by comparing the deformation measuring performance of the neural network changing the displacement range of images.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.235-239
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• 2008

Cable systems are a construction of elements carrying only tension and no compression or bending in membrane structure. Tensile membrane structures are most often used as roofs as they can economically and attractively span large distances. But cable systems have weaknesses to vibration by earthquake, wind and vehicle loads. Damage detection of cable systems by using existing safety diagnosis is difficult to detect the characteristic change of overall structural action. If cable snaps are occurred to cable release and tear in tension structures, these are set up a vibration. So, we used piezo-electric materials, and The principle of operation of a piezoelectric sensor is that a physical dimension, transformed into a force, acts on two opposing faces of the sensing element. In this study, the development on test method of cable system is proposed and tested by tensile strength using piezo-electric materials.

• Journal of Welding and Joining
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• v.23 no.4
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• pp.59-65
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• 2005

The resistance spot welding is one of the most commonly used welding process for joining the sheet metal in automotive manufacturing process due to higher deposition rates and higher economy achieved. Control variables in the resistance spot welding for achieving high quality are welding current, welding force and welding time. Generally at the manufacturing scene, welding current Vs welding time lobe diagram is used to estimate weldability because controlling welding force is not practical due to economical reasons. However new automotive steel plates have been developed to make lightweight automobiles and to improve resistance against rusting. Also the weldability of these steel plates are worst than the existing steel plates because of changing bare metal and surface plating effect. In consequence of above mentioned reasons, it is necessary to use welding force to present the lobe diagram. In this study, we obtained the welding force Vs welding current lobe diagram for commonly used GA steel plate and found that the second order repression model of tensile shear strength was useful in reducing the number of experiments, and the indentation, and thickness change during welding were used as a response to estimate quantitatively expulsion.

• Computers and Concrete
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• v.13 no.1
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• pp.49-70
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• 2014

Steel fiber-reinforced concrete (SFRC) is known as one of the efficient modern composites that can greatly enhance the material performance of cracked concrete in tension. Such improved tensile resistance mechanism at crack interfaces in SFRC members can be heavily influenced by methodologies of treatments of crack direction. While most existing studies have focused on developing the numerical analysis model with the rotating-angle theory, there are only few studies on finite element analysis models with the fixed-angle model approach. According to many existing experimental studies, the direction of principal stress rotated after the formation of initial fixed-cracks, but it was also observed that new cracks with completely different angles relative to the initial crack direction very rarely occurred. Therefore, this study introduced the direct tension force transfer model (DTFTM), in which tensile resistance of the fibers at the crack interface can be easily estimated, to the nonlinear finite element analysis algorithm with the fixed-angle theory, and the proposed model was also verified by comparing the analysis results to the SFRC shear panel test results. The secant modulus method adopted in this study for iterative calculations in nonlinear finite element analysis showed highly stable and fast convergence capability when it was applied to the fixed-angle theory. The deviation angle between the principal stress direction and the fixed-crack direction significantly increased as the tensile stresses in the steel fibers at crack interfaces increased, which implies that the deviation angle is very important in the estimation of the shear behavior of SFRC members.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.581-588
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• 2014

The PSC bridges have recently been widely used in Korea. The PSC bridge is a structure whose performance is improved through the use of tendons and steel bars in deflection and cracking characteristics of the concrete. Therefore, measurement or estimation of the load acting on tendon is important in order to maintain the PSC bridges efficiently and safely. This paper deals with a numerical study on the deformation of a multi-tendon anchor head in order to verify the relationship between the load acting on tendon and the deformation of anchor head. All kinematics, material properties and contact nonlinearity are included for the precise analysis and numerical studies are performed by Abaqus. From the numerical results, it is verified that the hoop strain is most useful in the estimation of the load acting on tendon and strains are affected by various parameters such as friction coefficient, boundary conditions, and arrangement.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.68-68
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• 2009

Recently, resistance spot welding using Inverter DC is applied to improve the weldability of high strength steel for the auto-body fabrication. In this study, inverter DC spot welding machine, which is developed in the domestic, was evaluated weldability of the galvanized and cold rolled dual-phase steel(tensile strength : 590MPa). The welding conditions (welding time, current and force) were decided by tensile-shear test, and welding strength and nugget size were analyzed by statistical analysis methods which involved dynamic resistance and indentation. The results of the statistical analysis was utilized for real-time estimation of the invisible nugget size and tensile strength. Moreover, it can be achieved without the conventional destructive testing of welds.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.47-53
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• 2022

As the limit state design method is applied as a method of designing concrete structures, the ultimate state is considered in the analysis or design. In fact, when the reinforced concrete member bears tensile force, the force is transmitted from the rebar to the concrete, and the structure bears the tensile force to the ultimate state even after yield. Therefore, the accurate evaluation of behavior after yield, it is necessary to study the tension stiffening effect after yield of the flexural member. In this study, a 4-point bending test was conducted on the RC simple beam having a rectangular cross section of the double reinforcement, and the behavior of the member was analyzed in detail using the image analysis method. Using the analysis results, the estimation formula for the tension stiffening effect after yield was proposed, and the applicability of this was verified through the experimental results of existing study. The difference between the ultimate strain and the yield strain representing the ductile behavior of the member is similar to the experimental results. The prediction of the proposed formula is relatively accurate.

• Coupled systems mechanics
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• v.12 no.5
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• pp.419-428
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• 2023

We have developed a model for estimating the parameters of viscous materials from indirect tensile tests for asphalt. This is a simple Burger nonlinear rheological two-cell model or standard model. At the same time, we begin to develop a more versatile and complex multi-cell model. The simple model is validated using experimental load-displacement results from laboratory tests: The recorded displacements are used as input values and the measured force data are simulated with the model. The optimal model parameters are estimated using the Levenberg-Marquardt method and a very good agreement between the experimental results and the model calculations is shown. However, not all parts of the model are active in the loading phase of the experiment, so we extended the validation of the model to the simulation of the relaxation behaviour. In this stage, the other model parameters are activated and the simulation results are consistent with the literature. At this stage, we have estimated the parameters only for the two-cell uniaxial model, but further work will include results for the multi-cell model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.997-1004
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• 2017

The life of elevator wire ropes is one of the most important characteristics of an elevator, which is closely related to the safety of users and its maintenance policy. It is not cost effective to measure the lifetime of elevator wire ropes during their use. In this study, the life estimation of elevator wire ropes (8x19W-IWRC) is considered using accelerated degradation test data. A bending fatigue tester is used to perform the accelerated degradation tests, incorporating the acceleration factor of tensile force. Assuming that the life of wire ropes is log-normally distributed, two life estimation methods are suggested and their results are compared. The first method estimates the life of wire ropes utilizing the accelerated life model with pseudo lives obtained from a linear regression model. The second method estimates the life using a logistic model based on failure probability.