• Structural Engineering and Mechanics
• /
• v.53 no.6
• /
• pp.1067-1081
• /
• 2015

This study investigates structural and mechanical behaviors of RC (Reinforced concrete) beams strengthened with tapered CFRP (Carbon fiber reinforced polymer) sheets having various configurations. Toward this goal, experiments are performed on RC beams strengthened with four layers of CFRP sheets and each layer of the CFRP is prepared to have different length. Experimental results show that tapered CFRPs have better strengthening effect than non-tapered CFRP sheets and maximum loads of the beams with tapered CFRPs are governed by the length of first CFRP layer rather than total length of CFRP layers. In addition, analyses are performed using FE (Finite Element) models including cohesive elements to predict debonding behaviors between FRP and concrete elements. The predicted results from the FE models show good agreement with the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.1
• /
• pp.18-26
• /
• 2012

Recently, research about Near-Surface-Mounted Rertofit (NSMR) method has been being widely performed as a method for retrofit of RC structure using FRP. This method requires additional work to make grooves during retrofit but makes it possible to improve retrofit effect and reduce the attack by environment. In this paper, the retrofit effect of NSMR method, especially the method using FRP plate instead of bar is investigated through experiment. Six RC beams were made and retrofitted using by FRP plate following the planned methods; Surface-Bonding Retrofit (SBR), NSMR without debonding region and NSMR with debonding region. Flexural capacity of all specimens was evaluated by beam test with simple support condition. As a result, NSMR method with FRP plate had more improved structural capacity than SBR method. The calculation process of ACI 440-2R can be used to predict the member retrofitted by NSMR with FRP plate with consideration on the three anchorage failure mechanism.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.6
• /
• pp.256-262
• /
• 2022

The purpose of this study is to define the shear reinforcing effect of Near-Surface-Mounted (NSM) FRP strips in reinforced concrete (RC) member through a test. Three T shaped RC beams were made and two of them were strengthened with NSM FRP strips for increase shear strength. And those were tested to find the shear strengthening effect. In the test, two case of shear strengthening methods were considered such as 1) with NSM FRP strips having full embedded length and 2) with NSM FRP strips having some what short embedded length and additional externally bonded FRP sheet. As a result, the shear strengthening effect could be obtained when the NSM FRP strips are embedded to have full length up to the bottom of slab. However the shear strength was not increased in the case of having somewhat short embedded length of NSM FRP strips even additional EB sheet was enhanced.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4A
• /
• pp.597-604
• /
• 2006

Fiber Reinforced Polymer (FRP) is a relatively new material in the bridge construction. With high strength to weight ratios, excellent durability, and low life-cycle costs of FRP, FRP bridge decks can offer a low dead load, reduced maintenance, and long service life. Due to the lightweight of FRP, if existing concrete decks can be replaced with the FRP decks, the load carrying capacity of superstructure can be increased without strengthening of girders. In this study, we have conducted an experiment on 7 cases of connection conditions with steel girder by using bolts considering a rational and economical method of connection and compared with the results of FEM analysis. From the experimental result, if the bolts are strong enough to resist shear force between the FRP bridge deck and the steel girder, it will be structurally secure to use the zigzag method.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.2
• /
• pp.697-703
• /
• 2017

This paper examines the flexure behavior of FRP-concrete composite structure that can replace conventional reinforced concrete structure types. In order to investigate the structural performance and behavioral characteristics in numerical analysis means, ABAQUS, a general purpose finite element analysis program, was utilized for nonlinear finite element analysis, and the various variables and their influences were analyzed and compared with experimental results to suggest values optimized to this composite structure. The concrete damage plasticity model and Euro code for concrete were used. In the implicit finite element analysis, the convergence was ambiguous when geometrical and material nonlinearity were large, so the explicit finite element analysis used in this study was deemed to be appropriate. From the comparison with the experiment about concrete damaged plasticity model, 20mm for the mesh size, $30^{\circ}$ for the dilation angle, $100Nmm/mm^2$ for the value of fracture energy, 0.667 for Kc value, and the consideration of damage parameter were suggested believed to be appropriate. The numerical model suggested in this study was able to imitate the ultimate load and cracking pattern very well; therefore, it is expected to be utilized in research of various new material composite structures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.1003-1006
• /
• 2003

In recent years, FRP plates have been studied for flexural reinforcement of RC structures due to easy installation and good Quality control. This study presents experimental field test results for the effectiveness of flexural reinforcement of the RC slab using external prestressing with thin CFRP strips made by the pultrusion process. It was demonstrated that flexural strength was considerably increased with relatively easy installation when compared to the other methods used for the composite reinforcement.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.10a
• /
• pp.697-702
• /
• 1997

This study presents test results of RC beams strengthened by carbon fiber sheet (CFS) or carbon fiber reinforced plastics (CFRP) for increasing shear resistance. Fifteen specimens were tested, and the test was performed with different parameters including the type of strengthening materials (CFS, CFRP), shear-strengthening methods (wing type, jacket type, strip type), strip-spacing, strengthening direction of FRP. The results show that shear-damaged RC beams strengthened by either CFS or CFRP have more improved the shear capacity.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.3
• /
• pp.84-92
• /
• 2008

This study is to investigate the flexural performance of Near Surface Mounted (NSM) strengthening method using Fiber reinforced Polymer (FRP) materials to concrete structures. For this study, the inverse-shaped trapezoid CFRP composite material which has been registered as New Excellent Technology (NET) 351 was adopted to the concrete structure. In this study, two types of the CFRP types were considered; Type A ($15{\times}13{\times}6mm$) and Type B ($4{\times}3{\times}10mm$) with different strengthening ratio. In the result of the test, it was proved that NSM strengthened specimens had more flexural performance of 20-100% than that of the unstrengthened specimen. With this test result, the structural efficiency was investigated based on the coefficient of ductility and coefficient of crack resistance.

• Structural Engineering and Mechanics
• /
• v.40 no.1
• /
• pp.105-120
• /
• 2011

The strengthening and rehabilitation of reinforced concrete structures with externally bonded carbon fibre reinforced polymer (FRP) laminates has shown excellent performance and, as a result, this technology is rapidly replacing steel plate bonding techniques. This paper addresses this issue, and presents results deals with the influence of external bonded CFRP-reinforcement on the time-dependent behavior of reinforced concrete beams. A total of eight reinforced concrete beams with cracked and un-cracked section, with and without externally bonded CFRP laminates, were investigated for their creep and shrinkage behavior. All the beams considered in this paper were simply supported and subjected to a uniform sustained loading for the period of six months. The main parameters of this study are two types of sustained load and different degrees of strengthening scheme for both cracked and un-cracked sections of beams. Both analytical and experimental work has been carried out on strengthened beams to investigate the cracking and deflection performance. The applied sustained load was 56% and 38% of the ultimate static capacities of the un-strengthened beams for cracked and un-cracked section respectively. The analytical values based on effective modulus method (EMM) are compared to the experimental results and it is found that the analytical values are in general give conservative estimates of the experimental results. It was concluded that the attachment of CFRP composite laminates has a positive influence on the long term performance of strengthened beams.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3A
• /
• pp.349-356
• /
• 2008

Recently FRP (Fiber Reinforcement Polymer) is widely used for the strengthening of damaged RC beams. Although many tests were carried out to verify flexural capacity of RC beams strengthened with FRP sheet or plate, the behavior of strengthened RC beams has not yet clearly verified. To investigate the strengthening efficiency of the Near Surface Mounted Reinforcement (NSMR) technique experimentally and analytically, a total of 7 specimens have been tested. The experimental results revealed that specimens strengthened with NSMR improved the flexural capacity of RC beams. Also, while the NSMR specimens utilized CFRP reinforcement efficiently compared to the EBR (Externally Bonded Reinforcement) specimen, the NSMR specimens still have debonding failure between epoxy and concrete interface. This study has proposed the model to predict failure modes and failure loads. Good agreement was obtained between the predicted and the experimental results.