• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.59-69
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• 2017

The tension load of the ground anchor inserted in the ground gradually changes over time. In this regard the change of the initial tension load is primarily decreased by the fixation condition of the fixing head and the mechanical characteristics of the tensile material. The subsequent additional tension load is a time-dependent loss mostly due to the fixing conditions of the bonded length and the surrounding ground properties of the field. In this paper, therefore, a measurement system using a relative displacement detector that can relatively easily measure the change of tension load is discussed. As a result of the review, it was confirmed that the results using the relative displacement detector are similar to those of the real scale model test, and it was also confirmed that similar results were obtained with the result of the pull-out test conducted on the ground anchors fixed to weathered rocks condition. In addition, a pull-out test was conducted on the test anchors whose initial tension load loss was relatively large and through this test pull-out behavior of the tension type ground anchors was verified.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.120-129
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• 2023

Hanger cable tension is a major response that can determine the integrity and safety of suspension bridges. In general, the vibration method is used to estimate hanger cable tension on operational suspension bridges. It measures natural frequencies from hanger cables and indirectly estimates tension using the geometry conditions of the hanger cables. This study estimated the hanger cable tension of the Palyeong Bridge using a vision-based system. The vision-based system used digital camcorders and tripods considering the convenience and economic efficiency of measurement. Measuring the natural frequencies for high-order modes required for the vibration method is difficult because the hanger cable response measured using the vision-based system is displacement-based. Therefore, this study proposed a back analysis technique for estimating tension using the natural frequencies of low-order modes. Optimization for the back analysis technique was performed by defining the difference between the natural frequencies of hanger cables measured in the field and those calculated using finite element analysis as the objective function. The direct search method that does not require the partial derivatives of the objective function was applied as the optimization method. The reliability and accuracy of the back analysis technique were verified by comparing the tension calculated using the method with that estimated using the vibration method. Tension was accurately estimated using the natural frequencies of low-order modes by applying the back analysis technique.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.175.1-175
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• 2001

This paper handles main automation facilities and important control issues for hot rolling mill processes. Starting from the general procedures of production cycle, detailed tension control applications are handled based on field experiences and published research papers. Nowadays, quality control and delivery time control for products is becoming more and more important as the client demand is tighter than any other period. In this respect, control technology in steel making process takes very important position. Therefore, the objective of this paper is to share control problems with the people in academic field and by doing so, to get new and striking solution for the problems.

• The Korean Journal of Pharmacology
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• v.26 no.2
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• pp.113-120
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• 1990

Influences of trigger calcium on myocardial contraction from several sources were investigated on the frequency reduction-induced changes of contraction in rat left atria driven by electrical field stimulation. Rat atria elicited characteristic three phase-changes according to frequency reduction: the first rapid rise in twitch tension, the second transient fast decrease in tension and the third maintenance of twitch tension at about 200% of resting tension during high frequency. Caffeine treatment enormously suppressed the frequency reduction-induced twitch tension increase. The atrial contraction during high frequency vanished after verapamil treatment. But, during low frequency, atrial contraction revived in the presence of verapamil. Ouabain treatment and sodium depletion in superfusing solution abolished the characteristic second phase with slow frequency. These results suggest that slow calcium channel is an indispensable calcium entry route and calcium release from sarcoplasmic reticulum is an major source for trigger calcium in cardiac contraction. And sodium-calcium exchange has a modulatory roles in the regualtion of trigger calcium according to the changes of intracellular sodium concentration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.58-66
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• 2023

In this study, cable tension was measured using the vibration method, and a vision-based system was applied as a sensor to measure the displacement response of a cable in a non-contact method. In the vision-based system, the camera is installed in a location that considers the target structure and the field of view of the camera. However, it can be difficult to recognize the control points required to measure the displacement response of a structure as the target structure and other structures such as vehicles may be included in the image at the intended installation location. In this study, a distorted image including a vehicle shows inaccurate results in image analysis due to the installation position of the vision-based system. Accordingly, the image including the vehicle was eliminated by calculating the similarity between the two images. To verify the validity of the method of estimating the cable tension of cable-stayed bridges using the proposed method, the vibration method was applied to cable-stayed bridges in service to measure the tension.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.67-74
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• 2006

The use of steel plates has been greatly increased in bridge construction, particularly for long-span bridges. For connections of those steel plates in the field, application of high-tension bold, such as M30, is highly demanded. However, the current steel construction specifications in Korea do not provide information for large-sized bolt connections. In order to evaluate the applicability of the large-sized high-tension bolt, this study experimentally investigates relaxation and slip behavior of M30 bolts with varying bolt size and plate thickness. In addition, internal compressive stress was computed using FEM analysis. The analyzed results were compared with the stress distribution measured from strain gages attached on bolts and bolt holes. From the study presented herein, the M30 high-tension bolts are anticipated to be successfully used with the relaxation less than 10% and the slip coefficient satisfying the specified limit.

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.17 no.2
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• pp.50-56
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• 2013

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.255-266
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• 2012

Main cable of a suspension bridge is the important member which shows the overall structure integrity at bridge completion. Configuration of main cable is a free hanging state at cable erection completion and is different from that at bridge completion supporting the dead loads such as hanger, girder, and so on. Accordingly, the configuration control under cable erection is considerably significant because the configuration at cable erection completion has direct influence on that at bridge completion. That is performed by sag adjustments at center, side span and tension adjustments at anchor span. The former needs the sag sensitivity which represents the control quantity of strand length corresponding to that of sag. The latter requires the tension sensitivity which shows the change of strand tension according to that of strand temperature. In this study, the fundamental equations of cable were derived with the assumption of either catenary or parabola shape, the differential-related equations using chain rule on horizontal tension were drawn from those and finally the estimation methods of the sag / tension sensitivity were proposed from both those. The nonlinear numerical analysis flow charts of sag sensitivity based on the catenary equations were proposed and the sag sensitivities grounded on the differential-related equations were compared with the results using them for various parameters of sag change. Also, considering the combinations of sag change parameters, the calculation method of the final variation for the cable sag was suggested. For the real suspension bridge under construction with PPWS method, the sag/tension sensitivity were estimated considering the construction conditions like the change of PPWS length, PPWS temperature, bridge span, etc.. We hope that this study will be a systematic guideline for the configuration control under main cable erection and improved highly by field verification in the real bridge site.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.176-187
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• 2015

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.24-32
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• 2002

The modified compression field theory is already applied in shear problem at some code(AASHTO-1998) partly. Nominal shear strength of concrete beam is sum of the concrete shcar strength and the steel shear strength in the current design code. But Torsional moment strength of concrete is neglected in the calculation of the nominal torsional moment strength of concrete beam In the current revised code. Tensile stress of concrete strut between cracks is still in effect due to tension stiffening effect. But The tensile stresses of concrete after cracking are neglected in bending and torsion In design. The torsional behavior is similar to the shear behavior in mechanics. Therefore the torsional moment strength of concrete should be concluded in the nominal torsional moment strength of reinforced concrete beam. This paper shows that the torsional moment strength of concrete is caused by the average principal tensile stress of concrete. To verify the validity of the proposed model, the nominal torsional moment strengths according to two ACI codes (89, 99) and proposed model are compared to experimental torsional moment strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.