• 대한정형도수물리치료학회지
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• 제29권1호
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• pp.1-9
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• 2023

BACKGROUND: The purpose of this study was to find out which exercise is more effective for the activation of the trunk, when the suspension plank and modified bridge exercise are performed. Weakening of the trunk muscles can lead to secondary injuries such as back injuries. In order to prevent injury, trunk muscles must be strengthened, and representative trunk strengthening exercises include planks and bridges. Each has been developed with a modified method, but since there is no paper comparing which exercise is more effective for trunk muscle strength, it was written to compare the two exercises. METHODS: The subjects were a random sample of 30 healthy men who agreed to participate in the study. The subjects were divided into two groups of 15 people each, and the suspension plank and the modified bridge exercise were performed for six weeks. The thickness of the transverse abdominis (TrA), internal abdominal oblique (IO), external abdominal oblique (EO), rectus abdominis (RA), multifidus (MF) was measured before and after the exercise. The two groups were analyzed using an independent t-test and paired t-test to compare the muscle thickness and the difference before and after exercise. RESULTS: The trunk muscle thickness was increased in both groups with suspension plank and modified bridge exercise, and there was a statistically significant difference. When comparing the two groups, the suspension plank group also showed a significant difference in RA (p<.05). CONCLUSION: As a result of this study, suspension plank exercise can have a positive effect on activating the trunk muscles and strengthening the strength of RA. Therefore, it is considered that suspension plank exercise is a more effective intervention to strengthen trunk muscle than modified bridge exercise.

• Geomechanics and Engineering
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• 제31권1호
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• pp.31-52
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• 2022

Investigating and evaluating the long-term creep behavior of historical buildings built on seismic zones is of great importance in terms of transferring these structures to future generations. Furthermore, assessing the earthquake behavior of historical structures such as masonry stone bridges is very important for the future and seismic safety of these structures. For this reason, in this study, earthquake analyses of a masonry stone bridge are carried out considering strong ground motions and various water levels. Tokatli masonry stone arch bridge that was built in the 10th century in Turkey-Karabük is selected for three-dimensional (3D) finite difference analyses and this bridge is modeled using FLAC3D software based on the three-dimensional finite difference method. Firstly, each stone element of the bridge is modeled separately and special stiffness parameters are defined between each stone element. Thanks to these parameters, the interaction conditions between each stone element are provided. Then, the Burger-Creep and Drucker-Prager material models are defined to arch material, rockfill material for evaluating the creep and seismic failure behaviors of the bridge. Besides, the boundaries of the 3D model of the bridge are modeled by considering the free-field and quiet boundary conditions, which were not considered in the past for the seismic behavior of masonry bridges. The bridge is analyzed for 6 different water levels and these water levels are 0 m, 30 m, 60 m, 70 m, 80 m, and 90 m, respectively. A total of 10 different seismic analyzes are performed and according to the seismic analysis results, it is concluded that historical stone bridges exhibit different seismic behaviors under different water levels. Moreover, it is openly seen that the water level is of great importance in terms of earthquake safety of historical stone bridges built in earthquake zones. For this reason, it is strongly recommended to consider the water levels while strengthening and analyzing the historical stone bridges.

• Advances in Computational Design
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• 제2권2호
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• pp.147-168
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• 2017

Over the past couple decades, externally bonded fiber reinforced polymer (FRP) composites have emerged as a repair and strengthening material for many concrete infrastructure applications. This paper presents an analytical investigation of the use of carbon FRP (CFRP) for a specific problem that occurs in concrete bridge girders wherein the girder ends are damaged by excessive exposure to deicing salts and numerous freezing/thawing cycles. A 3D finite element (FE) model of a full scale prestressed concrete (PC) I-girder is used to investigate the effect of damage to the cover concrete and stirrups in the end region of the girder. Parametric studies are performed using externally bonded CFRP shear laminates to determine the most effective repair schemes for the damaged end region under a short shear span-to-depth ratio. Experimental results on shear pull off tests of CFRP laminates that have undergone accelerated aging are used to calibrate a bond stress-slip model for the interface between the FRP and concrete substrate and approximate the reduced bond stress-slip properties associated with exposure to the environment that causes this type of end region damage. The results of these analyses indicate that this particular application of this material can be effective in recovering the original strength of PC bridge girders with damaged end regions, even after environmental aging.

• International Journal of Concrete Structures and Materials
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• 제1권1호
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• pp.29-36
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• 2007

The purpose of this paper is the assessment of the capacity of the reinforced concrete (RC) elements of an arch bridge when they are subjected to contact and near-contact explosive charges of various amounts, and the estimation of the critical charges for these components. The bridge considered is the Tenza Viaduct, a decommissioned structure south of Naples, Italy. Its primary elements, deck, piers and arches were analyzed. The evaluation was accomplished via numerical analyses that made possible to obtain the elements dynamic response when they are exposed to blast loading conditions. To evaluate the member's capacities, failure criteria for deck, piers and arches were proposed based on concrete damage parameters. Additionally, curves relating the explosive charge to the residual capacity and to damage level of the elements were also developed. The results of this work were taken into account to investigate the progressive collapse of the global structure.

• Steel and Composite Structures
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• 제30권3호
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• pp.231-251
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• 2019

In the present study, a numerical and experimental investigation has been carried out on the seismic behavior of RC columns of a bridge which damaged under corrosive environments and retrofitted by various techniques including combined application of CFRP sheets and steel profiles. A novel hybrid retrofitting procedure, including the application of inner steel profiles and outer peripheral CFRP sheets, has been proposed for strengthening purpose. Seven large-scale RC columns of a Girder Bridge have been tested in the laboratory under the influence of simultaneous application of constant axial load and the lateral cyclic displacements. Having verified the finite element modeling, using ABAQUS software, the effects of important parameters such as the corrosion percentage of steel rebars and the number of CFRP layers have been evaluated. Based on the results, retrofitting of RC columns of the bridge with the proposed technique was effective in improving some measures of structural performance such as lateral strength degradation and higher energy absorption capability. However, the displacement ductility was not considerably improved whereas the elastic stiffness of the specimens has been increased.

• PNF and Movement
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• 제17권3호
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• pp.441-450
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• 2019

Purpose: This study identified the co-activation of quadriceps and hamstring muscles during hamstring strengthening exercises in healthy adults. Methods: Twenty-one participants were required for the present study design to achieve 80% power, 0.8 effect size (η2), and an alpha level of 0.05. Thus, this study recruited 21 healthy adults. All participants performed Nordic exercises, bridge exercises, and one-leg deadlifts randomly. The activity of the rectus femoris, vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (SM) were measured. In addition, the ratios of VM/VL and hamstring/quadriceps (HQ) were measured during the three hamstring strengthening exercises using electromyography. One-way ANOVA was used to compare the co-activation of quadriceps and hamstring muscles in the three exercises. Results: The activity of VM and VL during the performance of one-leg deadlifts was significantly higher than the other two exercises. The BF had significantly higher activity during the Nordic exercises compared to the other two exercises. In addition, the SM activation was significantly greater during Nordic exercises than one-leg deadlifts. Additionally, there was significant difference in HQ ratio among hamstring strengthening exercises. In specific, the one-leg deadlifts yielded a significantly lower HQ ratio. Conclusion: This study revealed that one-leg deadlifts are effective in rehabilitation for anterior cruciate ligament injury. In addition, Nordic exercises can be recommended to facilitate hamstring muscle activation.

• Computers and Concrete
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• 제2권5호
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• pp.389-409
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• 2005

The Finite Element Analysis (FEA) is evidently a powerful tool for the analysis of structural concrete having nonlinearity and brittle failure properties. However, the result of FEA of structural concrete is sensitive to two modeling factors: the shear transfer coefficient (STC) for an open concrete crack and force convergence tolerance value (CONVTOL). Very limited work has been done to find the optimal FE Modeling (FEM) methodologies for structural concrete members strengthened with externally bonded FRP sheets. A total of 22 experimental deep beams with or without FRP flexure or/and shear strengthening systems are analyzed by nonlinear FEA using ANAYS program. For each experimental beams, an FE model with a total of 16 cases of modeling factor combinations are developed and analyzed to find the optimal FEM methodology. Two elements the SHELL63 and SOLID46 representing the material properties of FRP laminate are investigated and compared. The results of this research suggest that the optimal combination of modeling factor is STC of 0.25 and CONVTOL of 0.2. A SOLID 46 element representing the FRP strengthening system leads to better results than a SHELL 63 element does.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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• pp.158-161
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• 1991

By applying the newly developed techniques of polymer impregnated concrete (PIC) severely deteriorated and low quality concrete can be restored to an adequate structural material. Early deterioration of concrete causes severe problems for bridge deck concrete, pavement concrete for highways and airports, hydraulic structures and buiilding structures. Deterioration has its orgin in cracks on concrete surface, scaling of spalling due to freezing and thawing, neutralization of concrete, penetrations of water, salt, and calcium chloride. The objective of this study is to develope the new surface impregnants and strengthening techniques for them. It is found that the new impregnants and strengthening techniques developed in this study can retian the charecteristics of the existing concrete and decrease deterioration, and also increase durability, chemical resistance, strength, stiffness and ductility of the existing concrete.

• 한국구조물진단유지관리공학회 논문집
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• 제15권5호
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• pp.136-149
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• 2011

국내의 지형 특성으로 인해서 교량의 많은 부분이 슬래브교 형식이다. 차량이 대형화하고 교통량이 증가하면서 노후 슬래브교의 보강이 필요한 경우가 많다. 본 연구에서는 노후화된 슬래브교를 효과적으로 보강할 수 있는 외부 긴장재 보강공법을 제안하였다. 종방향 및 횡방향 외부 프리스트레싱을 이용한 네트형 보강법은 슬래브 중앙부의 처짐을 효과적으로 보강할 수 있는 방법이며, 하부공간을 침해하지 않으므로 실제 적용성이 뛰어나다. 실험을 통해서 제안한 보강법으로 인해서 향상되는 내하력의 크기를 검증하였다. 실험에서는 세 가지 서로 다른 하중조건에 대하여 처짐 및 변형률을 계측하여 보강의 효과를 비교, 분석하였다. 네트형 긴장재 보강 전후의 휨강성의 증가량은 재하 종류별로 30.7~107.3% 증가하였다. 보강 전후 처짐의 감소율은 27.6~52.2%에 달하였다. 종방향 및 횡방향 프리스트레싱으로 인한 네트형 보강법은 슬래브교의 중앙부 보강에 매우 효과적이며, 중앙에 집중되는 하중 뿐만 아니라 편기 재하되는 하중에 대해서도 유사한 보강효과가 있다. 또한 네트형 보강법은 필요에 따라 재긴장이 가능하므로 유지보수 및 사용성 측면에서 장점이라 할 수 있다.

• 대한통합의학회지
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• 제9권4호
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• pp.11-18
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• 2021

Purpose : The purpose of this study was to investigate the effect on lung capacity of healthy men and women in their twenties by performing an intervention using the chest extension exercise and the bridge exercise, which are respiratory muscle strengthening exercises. Methods : Thirty adult men and women in their 20s participated in this study. All subjects participated in the study after hearing the explanation of the purpose and method of the study, filling out a consent form. All subjects were randomly assigned to the chest extension exercise (CEE) group and the bridge exercise (BE) group of fifteen each. Each exercise was performed twice a week for 4 weeks. Lung capacity was measured by forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁) using spirometry. Lung capacity was measured before and after exercise. The measured data were compared through the dependent t-test and the independent t-test. The statistical significance level was set at .05. Results : After the intervention, the CEE group showed a significant increase in FVC and FEV₁ compared to before the intervention (p<.05). After the intervention, the BE group also had a significant increase in FVC and FEV₁ compared to before the intervention (p<.05). However, there was no difference in FVC and FEV₁ between groups before and after the intervention (p>.05). Conclusion : There was no difference between groups in lung capacity after exercise. However, both the chest extension exercise and the bridge exercise increased FVC and FEV1, which was thought to be because both exercise methods were effective in increasing lung capacity. Therefore, both chest extension exercises and bridge exercises can be effectively applied as a way to increase lung capacity.