• Structural Engineering and Mechanics
• /
• v.83 no.6
• /
• pp.799-810
• /
• 2022

This study investigated the effect of the strengthening efficiency of unbonded steel-bar truss system on the out-of-plane behavior of perforated masonry walls. Four full-scale unreinforced masonry (URM) walls with two different planes were prepared using the unbonded steel-bar truss system and a URM walls without strengthening. All masonry walls were tested under constant axial and cyclic lateral loads. The obtained test results indicated that the pinching effect in the out-plane behavior of masonry walls tends to decrease in the in- and out-of-plane strengthened URM walls using the unbonded steel-bar truss system with the higher prestressing force ratio (R_p) of vertical reinforcing bars in the unbonded steel-bar truss system, regardless of the perforated type of the masonry wall. Consequently, the highest maximum shear resistance and cumulative dissipated energy at peak load in the post-peak behavior were observed in the in- and out-plane strengthened URM walls with the highest R_p values, which are 2.7 and 6.0 times higher than those of URM. In particular, the strengthening efficiency of the unbonded steel-bar truss system was primarily attributed to the vertical prestressed steel-bars rather than the diagonal steel-bars, which indicates that the strains in the vertical prestressed steel-bars at the peak load were approximately 1.6 times higher than those in the diagonal steel-bars.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.411-416
• /
• 2002

With a rapid industrialization, repair and strengthening methods for a damaged bridges are raised a head in face of safety and reduction of physical distribution costs of bridges. Above all, external prestressing method has the high adaptability for concrete structures and the reliable effect of strengthening. Innovative ideas for bridges strengthening were considered along with established methods. That methods are identified, described. However there is not a systematic and categorized manual for external prestressing method. This study will provide a systematic and reliable manual with investigating the arrangement shape of cable and characteristics of brackets. And the key result of this study is an extensive compilation, which can be used by practicing engineers, of the most effective techniques for strengthening existing bridges.

• Journal of International Academy of Physical Therapy Research
• /
• v.3 no.1
• /
• pp.378-382
• /
• 2012

The purpose of this study effectiveness of core strengthening exercise programs on symmetric double limb support and balance ability for elderly. The subjects that 30 persons between the ages of 65~80 elderly participated were divided into two groups randomly for 8 weeks. Tetrax interactive balance system and Berg's balance scale were used to assess support and stability. Paired t-tests were used to evaluate the changes before and after intervention. The difference between the groups was compared using an independent t-test. The experimental group showed significantly increase weight support, stability, balance(p<.05). However, the control group not showed significantly increase weight support, stability, balance(p>.05). In a variation, experimental and control groups showed significantly increased rate of weight support, stability, balance(p<.05). Consequently, core strengthening exercise program should be considered as a therapeutic method for the elderly to improve the balance ability and effectiveness on falls.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.10a
• /
• pp.293-298
• /
• 1995

This study experimentally evaluate the bonding performance of repair and strengthening materials. It is very important problem to justify bonding properties between repair and strengthening materials and old concrete. Many previous research and investigation showed that bonding strength of reinforcing materials determines the strengthening effect and the durability of repair work. Therefore, menifestation of bonding properties and the improvement of bonding performance of repair and strengthening materials are very important. In order to improve the perforamnce of repair work, it needs to investigate the behavior of bonding materials, such as stress distribution along the bonding area and the long term performance of the material. The target repair methods are steel plate addition technique and repair mortar method, and the test parameters studied in this paper include epoxy thickness, bonding surface texture, and bonding area.

• Coupled systems mechanics
• /
• v.9 no.4
• /
• pp.359-379
• /
• 2020

Due to susceptibility of bridges in the past earthquakes, vulnerability assessment and strengthening of bridges has gained a particular significance. The objective of the present study is to employ an analytical method for the development of fragility curves, as well as to investigate the effect of strengthening on the RC box-girder bridges. Since fragility curves are used for pre-and post-earthquake planning, this paper has attempted to adopt the most reliable modeling assumptions in order to increase the reliability. Furthermore, to acknowledge the interaction of soil, abutment and pile, the effect of different strengthening methods, such as using steel jacketing and FRP layers, the effect of increase in the bridge pier diameter, and the effect of vertical component of earthquake on the vulnerability of bridges in this study, a three-span RC box-girder bridge was modeled in 9 different cases. Nonlinear dynamic analyses were carried out on the studied bridges subjected to 100 ground motion records via OpenSEES platform. Therefore, the fragility curves were plotted and compared in the four damage states. The results revealed that once the interaction of soil and abutment and the vertical component of the earthquake are accounted for in the calculations, the median fragility is reduced, implying that the bridge becomes more vulnerable. It was also confirmed that steel jackets and FRP layers are suitable methods for pier strengthening which reduces the vulnerability of the bridge.

• Physical Therapy Korea
• /
• v.23 no.4
• /
• pp.27-37
• /
• 2016

Background: In previous studies regarding flexible pes planus, Foot orthosis, special shoes have been used as interventions for correcting malalignment and intrinsic muscles strengthening exercise have been regarded as interventions for foot function and supporting medial longitudinal arch during walking. However, some recent studies reported that strengthening extrinsic muscles as well as intrinsic muscles is more effective and active intervention for flexible pes planus. In particular, the tibialis posterior muscle of foot extrinsic muscles plays essential roles in maintaining the medial longitudinal arch during dynamic weight bearing and balance. In addition this muscle acts longer than other supination muscles during the stance phase in the gait cycle. Objects: This study aimed to investigate the effect of foot intrinsic muscle and tibialis posterior muscle strengthening exercise for plantar pressure and dynamic balance in adults with flexible pes planus. Methods: 16 young flexible pes planus adults (7 males, 9 females) were recruited and were randomized into two groups. The experimental group performed foot intrinsic muscle and tibialis posterior muscle strengthening training, the control group performed only foot intrinsic muscle strengthening training. All groups received strengthening training for 30 minutes five times a week for six weeks. Results: The experimental group had significantly lower plantar pressure of medial heel area than the control group in stand (p<.05). The experimental group had significantly higher dynamic balance ability than control group (p<.05). Conclusion: The results of this study provide evidence to suggest that foot intrinsic muscle and tibialis posterior muscle of extrinsic muscle strengthening exercises may improve plantar pressure distribution and dynamic balance ability in adults with flexible pes planus.

• Journal of the Korean Society of Physical Medicine
• /
• v.6 no.2
• /
• pp.165-175
• /
• 2011

Purpose: This study examined the effect of the strengthening exercise and stretching exercise to decrease symptom patellofemoral pain syndrome (PFPS). Methods: The Anterior Knee Pain Scale (AKPS) and Clark's test performed for diagnosis of intrinsic PFPS among young adults. Selected thirty young adults subjects who aged 20~26 years participated in the study. Participants were randomly assigned to strengthening, stretching, or control groups. Strengthening group consisted of quadriceps, hamstring and iliotibia band training used elastic band. Stretching group consisted of quadriceps, hamstring and iliotibia band trainings used stretching exercises program. Participants received 50-minute individualized exercise sessions, 3 times a week for 6 weeks. Results: The results were as follow: there were significantly difference stretching exercise group by all muscles on muscular strength test (p<.05). there were significantly difference both strengthening and stretching exercise group by all muscles on flexibility test (p<.05). There were significantly difference stretching exercise group by all muscles on step-down test (p<.05). There were significantly difference both strengthening and stretching exercise group by all muscles on visual analog scale (p<.05). Conclusion: Results suggest important implications for exercise programs of PFPS that stretching exercise is more improved knee pain, functional performance, patella mobility than strengthening exercise.

• Journal of Korean Academy of Nursing
• /
• v.26 no.3
• /
• pp.556-575
• /
• 1996

In an attempt to investigate the effect of a muscle strengthening exercise program on muscle strength, pain, depression, self-efficacy and quality of life of patients with knee osteoarthritis, a pre-experiment, one group pre-test & post-test design, was planned. Muscle strengthening exercise was carried out from May 22 through August 14, 1995 at isokinetic exercise room in rehabilitation department of University Hospital in Taejon. The subjects were seven female clients conveniently sampled from University Hospital located in Taejon, between 39 and 61 years of age, who had a osteoarthritis in knee. Muscle strengthening exercise program was composed of three sessions per week, one isokinetic exercise at angular velocity of 60° and 180° with Cybex isokinetic dynamometer and two resistance home exercise sessions with elastic band. Data were analyzed with frequency, percentage of change, Friedman test, Duncan test using SAS program. Results were obtained as follows : 1) Flexion and extension muscle strength at angular velocity of 60° and 180° were increased after 12weeks' exercise than those of before experiment. But exept flexion muscle strength at angular velocity of 180°(F=3.34, P=0.0261), there was no statistically significant difference among muscle strengths, which is measured every 3 weeks. 2) Pain was decreased after 6weeks' exercise than that of before experiment, and after 12weeks' exercise than that of 6weeks' exercise. There was statistically significant difference (F=4.28, P=0.0396). 3) Depression was increased after 6weeks' exercise than that of before experiment, and after 12weeks' execise than that of 6weeks' exercise. There was no statistically significant difference between before experiment and after 6weeks' exercise. But, there was statistically significant difference between after 6weeks' exercise and 12weeks' exercise(F=9.38, P=0.0035). 4) Self-efficacy was decreased after 6weeks' exercise than that of before exercise. But, it was increased after 12weeks' exercise than that of be-fore exercise and after 6weeks' exercise. But there was no statistically significant difference (F=1.46, P=0.2706). 5) Quality of life was increased after 6weeks' exercise than that of before exercise, and after 6weeks' exercise than that of 12weeks' exercise. But there was no statistically significant differ once (F=1.06, P=0.3816). Thus, the significant of muscle strengthening exercise for the improvement of muscle strength, pain, depression, is verified. But, this study was a pre-experiment with small size subjects. So, con-trolled experimental study is necessary to determine the effect of this muscle strengthening exercise program on muscle strength, pain, depression, self-efficacy, and quality of life of patients with knee osteoarthritis.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.1
• /
• pp.171-178
• /
• 2019

Fiber-reinforced polymer (FRP) composites have proved to be reliable as strengthening materials. Most of existing studies used single types of FRP composites. Therefore, in this experimental study, carbon FRP sheet, aramid FRP sheet, and hybrid FRP plate including glass fibers were fabricated, and the effect of pre-stressed FRP composites on flexural strengthening of reinforced concrete (RC) beams was investigated. In total, eight RC beam specimens were fabricated, including one control beam (specimen N) without FRP composites and seven FRP-strengthened beams. The main parameters were type of FRP composite, the number of anchors used for pre-stressing, and thickness of FRP plates. As a result, the beam strengthened with pre-stressed FRP plate showed superior performance to the non-strengthened one in terms of initial strength, strength and stiffness at yielding, and ultimate strength. As the number of anchors and thickness of FRP plate (i.e., amount of FRP plates) increased, the strengthening effect increased as well. When hybrid FRP plates were pre-stressed, the strengthening effect was higher in comparison with pre-stressed single type FRP plate.

• Journal of Korea Foundry Society
• /
• v.11 no.4
• /
• pp.293-302
• /
• 1991

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by a combined technique of rheo-compocasting and hot extrusion. Distribution of fibers in the composites fabricated by rheo-compocasting was relatively uniform. A good degree of uniaxial fiber alignment has been achieved by hot extrusion, but a lot of fibers fractured during extrusion. The tendency of fiber fracturing increases as the aspect ratio and the amount of fibers increase. Relatively good bonding between fiber and matrix was obtained by the formation of $MgAl_2O_4$ and Mg(Al, Fe)$_2O_4$ at the interface between fiber and matrix. In extruded composites, fiber-strengthening effect was relatively small since a lot of fibers fractured during hot extrusion. On the other hand, dispersion strengthening effect may increase. In order to improve the fiber strengthening effect, it is important to optimize the extrusion condition with consideration of metal flow in extrusion die.