• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.4A
• /
• pp.279-286
• /
• 2011

FRP (Fiber Reinforced Polymer) tendons can be used as an alternative to solve the corrosion problem of steel tendons. Material properties of FRP tendons-bond strength, transfer length, development length-must be determined in order to apply to concrete structures. First of all, in case of application for pretension concrete members with CFRP tendons, transfer length is an important characteristic. The bond of the material characteristics should be demanded clearly to apply to PSC structures prestressed with FRP tendons. This paper investigated on the bond characteristics of FRP reinforcements with various surface-type. To determine the bond characteristics of FRP materials used in place of steel reinforcement or prestressing tendon in concrete, pull-out testing suggested by CAN/CSA S806-02 was performed. A total of 40 specimens were made of concrete cube with steel strands, deformed steel bar and 6 different surface shape FRP materials like carbon or E-glass. Results of the bonding tests presented that each specimen showed various behaviors as the bond stress-slip curve and compared with the bond characteristic of CFRP tendon developed in Korea.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.3
• /
• pp.37-43
• /
• 2006

Six types of hat stiffened composite panels were manufactured with different bonding methods and stiffener section shapes and compression testing of these panels were performed. The panels showed similar behaviors in bucking and postbuckling region before a skin-stiffener separation failure occurred. Although all the separation failures occurred at the same locations of stiffener flanges close by skin buckling crests, the separation loads, separation failure growth behaviors and final collapse loads were different with respect to bonding methods and stiffener section shapes. As the separation failure initiated early and propagated larger area, collapse loads and structural efficiency of the panels decreased.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.121-124
• /
• 2008

The purpose of this study is to evaluate the critical strengthening ratio of concrete railroad bridge strengthened with NSM using CFRP plate. The railroad bridge is usually under vibration and impact in service state. Therefore, it is important that the effective strengthening performance must be exhibited under the service loading is acted. To widely apply the NSM method for the concrete railroad bridge in field, it needs that reasonable strengthening parameter such as strengthening ratio has to be investigated and evaluated when the strengthening design is conducted. In this study, to suggest more reasonable strengthening ratio, material and geometrical uncertainty was considered and applied by Monte Carlo Simulation (MSC) technique. Lastly, the critical strengthening ratio of concrete railroad bridge strengthened with NSM using CFRP plate was evaluated by using the limit state function with the target reliability index.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.19 no.2 s.72
• /
• pp.195-202
• /
• 2006

Thin-walled structures are efficiently utilized an automobiles, aircraft, satellite and ship as well as needed light weight simultaneously. This paper presents new shape of automobile hood reinforcement that rotating parts as engine, transmission are protected by thin-walled structures. The automobile hood is concerned about the resonance occurs due to the frequency of the rotating parts. The hood must be designed by supporting the stiffness of design loads and considering the natural frequencies. Hence, it is sustained the stiffness and considered the vibration by resonance. It is deep related to ride. Therefore, the topology, shape and size optimization methods are used to design the automobile hood. Topology technique is applied to determine the layout of a structural component optimum size with maximized natural frequency by volume reduction. In this research, The optimal structure layout of an inner reinforcement of an automobile hood for the natural frequency of a designated mode is obtained by using topology optimization method. The optimum size and the optimum shape are determined by PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm.

• Composites Research
• /
• v.33 no.6
• /
• pp.377-382
• /
• 2020

The free vibration characteristics of corrugated laminated composite plates with axial stiffeners is investigated using the Rayleigh-Ritz method. The plate is stiffened by beams with open cross-section area. The equivalent homogenization model is used for the corrugated laminated composite plates. This homogenization model is treated a corrugated plate as an orthotropic plate that has different material properties in two perpendicular directions. The motion of equivalent plate is represented on the basis of the first order shear deformation theory (FSDT) to account for the effect of rotary inertia and transverse shear deformation. Stiffeners are considered as discrete elements to predict the local vibration mode to be generated by the presence of stiffeners. To validate the proposed analytical approach, natural frequencies and vibration mode shapes from the analytical method are compared with those from the FEA by ANSYS.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.4
• /
• pp.241-249
• /
• 2017

In a reinforced soil structure, the interaction between soil and an reinforcement occurs due to the frictional resistance on the contact surface between them or the pullout resistance of the reinforcement. Generally, a pullout test is conducted to measure pullout parameters of extensible geogrids. The factors affecting the pullout parameters in a pullout test include a density of backfill, shape of reinforcements, overburden pressure, length of spread reinforcements, and so on. The purpose of this study is to suggest a length of the spreading of an extensible reinforcement that can be used in estimating suitable pullout parameters of a pullout test. To this end, a pullout test was carried out. For the test, the length of spreading of an extensible reinforcement was set as 32 cm, 52 cm, 72 cm, and 100 cm, and effects of the lengths on pullout parameters were analyzed. As a result of the pullout test, it was confirmed that the frictional resistance between the soil and the reinforcement increases with the increase of the length of the reinforcement.

• Applied Chemistry for Engineering
• /
• v.10 no.5
• /
• pp.789-795
• /
• 1999

In this study, carbon fiber reinforced cement composites(CFRCs) reinforced with short noncircular type carbon fibers were fabricated and properties(drying shrinkage, resistance to freezing and thawing, and fracture toughness) were compared with those of the CFRCs reinforced with circular type carbon fibers. It was found that these properties greatly depended on the shape and length of carbon fibers. The drying shrinkage of CFRCs reinforced with C-type carbon fiber was superior to other CFRCs. This effect was increased with a high aspect ratio of fiber. The resistance to freezing and thawing was increased with the fiber length and fiber volume percent, but there was on remarkable effect to fiber shape. Fracture toughness and resistance to crack propagation of CFRCs reinforced with C-CFs were improved compared with other CFRCs. It was believed that the more absorption of fracture energy into the larger interface caused an increase in fracture toughness and resistance to crack propagation.

• Proceedings of the KWS Conference
• /
• 1993.10a
• /
• pp.125-128
• /
• 1993

• Journal of Korean Society of Steel Construction
• /
• v.17 no.5 s.78
• /
• pp.527-536
• /
• 2005

A method of reinforcement using external tendons has been found to be one of the effective techniques of reinforcement and its application is increasing. In this paper, the method to calculate the initial tendon force is proposed for the improvement of load-carrying capacity in existing steel-concrete composite bridges. An equation for the increment of tendon force was derived for tendon configurations and live load types, and the effect of reinforcement in a composite beam was numerically studied. The method to calculate the number of tendon and initial tendon force was presented by proposing the new method to calculate the rating factor, which considers the increment of tendon force. The method was shown to be effective for an existing steel-concrete bridge.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.8
• /
• pp.661-669
• /
• 2021

A mechanical stiffener has been mainly applied on a PCB to secure fatigue life of a solder joint of an electronic components in spaceborne electronics by minimizing bending displacement of the PCB. However, it causes an increase of mass and volume of the electronics. The high damping PCB implemented by multi-layered viscoelastic tapes of a previous research was effective for assuring the fatigue life of the solder joint, but it also has a limitation to decrease accommodation efficiency for the components on the PCB. In this study, we proposed high damping PCB with a multi-layered superelastic shape memory alloy stiffener for spatialminimized, light-weighted, high-integrated structure design of the electronics. To investigate the basic characteristics of the proposed PCB, a static load test, a free vibration test were performed. Then, the high damping characteristic and the design effectiveness of the PCB were validated through a random vibration test.