• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2632-2640
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• 2012

The purpose of this study was to investigate whether medial gastrocnemius ultrasound imaging of the Delayed Onset Muscle Soreness (DOMS) has the possibilities as a measurement method. This study was conducted from April 21th 2011 to April 30th 2011. Thirty-five healthy subjects were included based on the absence of regular physical activity, and no history of recent trauma, musculoskeletal pathology, cardiovascular disease or drug intake. All subjects induced DOMS through climbing for 5 hours and we measured the visual analogue scale (VAS), creatine kinase (CK) and maximal voluntary isometric contraction (MVlC) of ankle plantar flexor prior to DOMS and at 24, 48 and 72 hours post DOMS and these measurements were compared with pennation angle of medial gastrocnemius measured by ultrasound imaging. Results of this study were as following. VAS, CK, and MVIC of ankle plantar flexor were found significant difference related measurement period (p<0.05) and pennation angle of medial gastrocnemius were found significant difference related measurement period (p<0.05). Furthermore, we confirmed that the flow of change between variables related measurment period was consistent. Through this study, we think that measuring the changes in pennation angle of medial gastrocnemius over time using ultrasound imaging will be able to be used as a new method measuring DOMS.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.543-555
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• 1997

Generally, in a steel-concrete composite gilder, the shear connector which was constructed between concrete deck and steel girder should have enough stiffness to behave as one body, because the conformity between plate and concrete deck is influences by the stiffness and spacing of the shear connectors. If the stiffness of shear connectors are insufficient, slip would happen at the contact surface. Partial interaction is the case that takes account of slips. In this paper, an easy method is presented to evaluate the stiffness or spacing of the shear connector according to the degree of imperfection without difficult calculations for a composite gilder with partial interaction. Also, the horizontal shearing force applied to the shear connector and the longitudinal axial force, which is occurs at contact surface between concrete deck and steel girder, have been presented in a simple influence line that is various to the parameters of sectional properties, degree of imperfection and applied load points. Furthermore, through the case study, it determined the relationships between the degree of imperfection and the follows 1) spring constants 2) axial force and horizontal shearing force 3) stress and neutral axis by using the partial differential equation based on Newmark's Partial Interaction Theory.

• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.13-22
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• 2015

In the current work, a series of three-dimensional (3D) numerical modelling has been performed in order to study the effects of the relative locations of tunnels with respect to the position of pile tips which governs the behaviour of pre-existing, adjacent single piles. In the numerical analyses, several governing factors, such as tunnelling-induced pile head settlements, relative displacements, volume losses, axial pile forces, interface shear stresses and apparent factors of safety have been analysed. When the pile tips are inside the tunnelling influence zone, of which the pile tip location is considered with respect to the tunnel position, tunnelling-induced pile head settlements are larger than the ground surface settlements, resulting in tunnelling-induced tensile pile forces. On the contrary, when the pile tips are outside the influence zone, compressive pile forces associated with downward shear stresses at the upper part of the piles are developed. Based on computed load and displacement relation of the pile, the apparent factors of safety of the piles inside the tunnelling influence zone have been reduced by 36% in average. The shear transfer mechanism based on the relative tunnel locations has been analysed in great detail by considering tunnelling-induced pile forces, interface shear stresses and the apparent factors of safety.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.279-299
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• 2019

Recently occurred earthquake Gyeongju and Pohang served as a momentum to remind that Korean peninsular is not a safety zone from earthquake anymore. The importance of seismic design, therefore, have been realized and researches regarding design response spectrum have been actively carried out by many researchers and engineers. Current tunnel seismic design method is conducted to check safety of tunnel structure by dynamic numerical analysis with condition of completed lining installation, so, it is impossible to consider safety of tunnel behavior under construction. In this study, therefore, dynamic numerical analysis considering seismic wave propagations has been performed after back analysis using results from field monitoring of tunnel under construction in fractured zone and 1st reinforcement (shotcrete, rockbolt) behaviour are analyzed. Waves are classified by period characteristic (short and long). As a result, the difference depending on period characteristic is minor, and increasements of displacement are obtained at crown displacement due to seismic wave is 28~31%, 14~16% at left side of tunnel in the fractured zone, 13~27% at right side of tunnel in the bed rock, respectively. In case of shotcrete axial force is increased 113~115% at tunnel crown, 102% at left side, 106~110% at right side, respectively. Displacement and axial force of rockbolts which are selected by type of anchored grounds (only fractured zone, fractured zone and bed rock, only bedrock) are analyzed, as a result, rockbolt which is anchored to fractured zone and bed rock at the same time are weaker than any other case.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.641-652
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• 2007

In this paper, a half-scaled substructure test was performed to evaluate the buckling and structural safety of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads of a prototype transmission tower, which uses a triangular jig that is mounted on the reduced model to which the similarity law of a half length was applied. As a result of the preliminary numerical analysis carried out to evaluate the stability of a specimen for the design load, is was confirmed that the calculated axial forces of tower leg members were distributed to $80{\sim}90%$ of an admissible buckling load. When the substructured transmission tower was loaded by 270% of its maximum admissible buckling load, it was failed due to the local buckling that is occurred in joints with weak constraints for out-of-plane behavior of leg members. By inspection of load-displacement curves, displacements and strains of members, it is considered that this local buckling was due to additional eccentric force by unbalanced deformation because the time that is reached to yielding stress due to the bending moment is different at each point of a same section.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.59-71
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• 2012

Results of the analysis of the structural behavior of axially loaded nodes in freeform structure were not fully understood due to certain difficulties, including the application of various welding and bolting types. In this study, a node of single layered freeform structure was tested to determine its structural behavior when subjected to axial loads. The tests were classified into node ball tests to evaluate the center of the node subjected to cyclic and monotonic loading. The node part tests were also conducted to evaluate the whole node subjected to monotonic loading. The test showed that the node ball is safe with the tensile force, but the node ball needs to increase its strength with the node loaded compressive force due to the additional bending moment of the node ball's asymmetric form.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.315-326
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• 2004

This study performed model tunnel tests in order to investigate the influence of discontinuity condition of rock mass to the stress and deformation of tunnel lining. Tests were carried out changing the direction of main joint and lateral earth pressure condition of rock mass. Test results revealed that the axial force in tunnel lining showed a tendency of decrease with the presence of joints. It decreased much with the increase of lateral earth pressure coefficient. And, it also showed that the location or maximum displacement and maximum stress in lining were changed by the direction of main joint of rock mass. The tangential stress and normal stress showed the difference above the maximum twenty times as lateral earth pressure coefficient due to effect of joints increased. Also, these tendencies of concentration of tensile stress in tunnel lining were confirmed by elastic theory.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.93-96
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• 2008

This paper deals with the shaking table test(STT), the Quasi-Static Test(QST), and the Pseudo-Dynamic Test(PDT) to evaluate the seismic performance of RC bridge piers under near fault ground motion. Five scaled specimens were constructed the weight of the superstructure was applied through the prestressing strand at the centroid of the column section during the QST and PDT. However, the STT was simulated. The lateral inertia force of the superstructure by the mass frame which was linked with the pier because of the limited payload of shaking table. Particularly for the STT, friction underneath the mass frame was minimized by special details and it was verified by a series of pre-load test. Scale factor of the RC piers was 4.25.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.535-546
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• 2010

Recently, the probability of collision accident between vehicles or vessels and infrastructures are increasing at alarming rate. Particularly, collision impact load can be detrimental to sub-structures such as piers and columns. The damaged pier from an impact load of a vehicle or a vessel can lead to member damages, which make the member more vulnerable to impact load due to other accidents which. In extreme case, may cause structural collapse. Therefore, in this study, the vehicle impact load on concrete compression member was considered to assess the quantitative design resistance capacity to improve, the existing design method and to setup the new damage assessment method. The case study was carried out using the LS-DYNA, an explicit finite element analysis program. The parameters for the case study were cross-section variation of pier, impact load angle, permanent axial load and axial load ratio, concrete strength, longitudinal and lateral rebar ratios, and slenderness ratio. Using the analysis results, the performance based resistance capacity evaluation method for impact load using satisfaction curve was developed using Bayesian probabilistic method, which can be applied to reinforced concrete column design for impact loads.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.147-156
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• 1999

An investigation was conducted into the flexural behavior of earthquake damaged reinforced concrete columns repaired with carbon fiber sheets. Six column specimens were tested to failure under reversed cyclic loading. Two columns were specimens for control with no sheets and tested. These columns were repaired with carbon fiber sheets and retested to evaluate the effect of the confinement of the carbon fiber on the damaged column. Another two columns were repaired and tested with no pre-cyclic loading. The test specimens were designed to model single bent under a constant axial force with reversed cyclic lateral loading. Carbon fiber sheets were used to repair damaged concrete columns in the critically stressed areas near the column footing joint and the physical, mechanical properties of carbon fiber sheets are described. The performance of repaired columns in terms of their hysteretic response is evaluated and compared to those of the original columns. The results indicate that the repaire technique with carbon fiber sheets is highly effective. Both flexural strength and displacement ductility of repaired columns were higher than those of the original columns.