• Steel and Composite Structures
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• v.23 no.4
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• pp.385-397
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• 2017

Currently, CFRP (Carbon Fiber Reinforced Polymer) plate bonding is used quite extensively as a strengthening method. In this technique, a composite CFRP plate or sheet of relatively small thickness is bonded with an adhesion material to steel or concrete structure in order to improve its structural behavior and strength. The sheets or plates do not require much space and give a composite action between the adherents. In this study, the rotation capacity of CFRP-strengthened cold-formed steel (CFS) beams has been evaluated through numerical investigation. Studies on different structural levels have been performed. At the beam level, C-section has been adopted with different values of profile thickness, web height, and flange width. At the connection level, a web bolted moment resistant type of connection using through plate has been adopted. In web-bolted connections without CFRP strengthening, premature web buckling results in early loss of strength. Hence, CFRP sheets and plates with different mechanical properties and geometric configurations have been examined to delay web and flange buckling and to produce relatively high moment strength and rotation capacity. The numerical results reveal that CFRP strengthening may increase strength, initial stiffness, and rotation capacity when compared with the case without strengthening.

• Computers and Concrete
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• v.30 no.1
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• pp.75-83
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• 2022

This study introduced a post-tensioned precast concrete system that was developed and designed to improve the performance of joints by post-tensioning. Full-scaled specimens were tested to investigate flexural performances at the negative moment region, where the test variables were the presence of slabs, tendon types, and post-tensioned lengths. A specimen with slabs exhibited significantly higher stiffness and strength values than a specimen without slabs. Thus, it would be reasonable to consider the effects of a slab on the flexural strength for an economical design. A specimen with unbonded mono-tendons had slightly lower initial stiffness and flexural strength values than a specimen with bonded multi-tendons but showed greater flexural strength than the value specified in the design codes. The post-tensioned length was found to have no significant impact on the flexural behavior of the proposed post-tensioned precast concrete system. In addition, a finite element analysis was conducted on the proposed post-tensioned precast concrete system, and the tests and analysis results were compared in detail.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.283-294
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• 2013

The high strength materials have been more widely used in reinforced concrete structures, specially, the reinforcing steel is permitted to used in RC structures up to yielding strength of 600 MPa. The strength of materials in RC beam section effects on the behavior and ductility of the RC members. In this study, the numerical analysis has been conducted to obtain the complete moment-curvature relation and the curvature ductility factor for the rectangular RC beams sections under the various reinforcement conditions and the effects of concrete strength, yield strength of reinforcement steel on the behavior and the curvature ductility factor of RC beam sections have been evaluated. The compressive strength of concrete and yield strength of steel have effected in various manner on the behavior and the curvature ductility factor of RC beam sections under reinforcement conditions. In the case of beam sections with equal resisting moment. the curvature ductility factor of RC beam section decreased with an increase in the yield strength of steel and increased with an increase in the concrete strength. When the yield strength of steel increased from 400 MPa to 600 MPa, the curvature ductility factor reduced about 30% and as the concrete strength increased from 30 MPa to 70 MPa, the curvature ductility factor of RC beam section increased about 3 times.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.587-592
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• 2002

This study attempts to calculate tile nominal flexural strength of reinforced concrete beam with carbon fiber sheets by tile 27 cases which have three steel ratios and four reinforcing ratios. Based on the result, application possibilities of strength design method to estimate the nominal moment is investigated and valuable data of carbon fiber sheets for reinforcing design will be discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.69-72
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• 2005

For reinforced concrete column under sustained loads, the member suffers additional lateral deflection due to creep. This deflection leads to additional bending in the member, which in turn causes the column to deflect still further. Therefore the secondary moment due to additional deflection causes an increase in primary moment and the strength of column is reduced. And also creep buckling may occur. On this study, nonlinear analysis of reinforced concrete long column including crack effects is carried out and then the strength of long column is revaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.365-372
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• 1997

This study is aimed for manufacturing a High performance Concrete(HPC) Pile as using steel fibers, investigation the mechanical properties of HPC Pile and proposition the potential application. At this study. We found that mechanical properties(cracking moment and fracture moment) of Pretensioned spun High strength Concrete (PHC) Pile using steel fibers is much superior to without steel fibers. Therefore. we think that using steel fibers in Concrete Pile is to progress flexural strength energy absorption capacity and post-cracking resistance.

• Journal of The Korean Society of Integrative Medicine
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• v.5 no.4
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• pp.41-48
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• 2017

Purpose : The purpose of this study was to verify the relationships among the knee adduction moment, hip rotation range, strength of hip rotators, and Foot Posture Index of healthy young adults. Method : Thirty-two healthy adults(24 male, 8 females) participated in this study. Subjects performed 5 walking trials to evaluate the knee adduction moments using a three-dimensional motion analysis system. Hip rotation ranges and hip rotator strengths were measured using a standard goniometer and a handheld dynamometer, respectively. The mean of three trials of clinical tests was used for data analysis. Results : The first peak knee adduction moment was significantly correlated with the hip rotation ranges and hip rotator strengths (P<.05). The second peak knee adduction moment was showed significant correlations with hip external rotation and rotation ratio. There were no correlations between Foot Posture Index and all knee adduction moments (P>.05). Conclusion : This study suggests that imbalances of the range of motion and strength of the internal and external rotation of the hip joint can affect knee adduction moments. The impact may exacerbate musculoskeletal disorders such as osteoarthritis of the knee. Therefore, further studies should be conducted to evaluate the effects of clinical interventions to correct these imbalances on the reduction of the knee adduction moments in patients with knee osteoarthritis.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.33-46
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• 1999

In spite of 6.8 magnitude and the neighborhood of the epicenter, the steel moment frame survived after Northridge earthquake without collapse or casualties. However, following investigation revealed that there were severe damages at the column-weld interface of welded flange-bolted web (WFBW) steel moment connection, which was believed to be economic and safe from earthquakes based on experience and past tests. In this paper, this unexpected brittle fracture of the steel moment connection is explored using linear elastic fracture mechanics and post-Northridge tests. A method to predict the brittle fracture strength of the steel moment connection is proposed. Using this method, the failure mode of the WFBW connection and reduced beam section (RBS) connection are presented.

• Steel and Composite Structures
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• v.1 no.1
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• pp.145-158
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• 2001

An experimental study was conducted to evaluate the effects of loading sequence and lateral bracing on the behavior of reduced beam section (RBS) steel moment frame connections. Four full-scale moment connections were cyclically tested-two with a standard loading history and the other two with a near-fault loading history. All specimens reached at least 0.03 radian of plastic rotation without brittle fracture of the beam flange groove welds. Two specimens tested with the nearfault loading protocol reached at least 0.05 radian of plastic rotation, and both experienced smaller buckling amplitudes at comparable drift levels. Energy dissipation capacities were insensitive to the types of loading protocol used. Adding a lateral bracing near the RBS region produced a higher plastic rotation; the strength degradation and buckling amplitude were reduced. A non-linear finite element analysis of a one-and-a-half-bay beam-column subassembly was also conducted to study the system restraint effect. The study showed that the axial restraint of the beam could significantly reduce the strength degradation and buckling amplitude at higher deformation levels.

• Steel and Composite Structures
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• v.32 no.4
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• pp.497-507
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• 2019

Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.