• Computers and Concrete
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• v.33 no.2
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• pp.163-173
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• 2024

Fiber-reinforced polymers (FRP) have a proven strength enhancement capability when installed into Reinforced Concrete (RC) beams. The brittle failure of traditional FRP strengthening systems has attracted researchers to develop novel materials with improved strength and ductility properties. One such material is that known as polyethylene terephthalate (PET). This study presents a numerical investigation of the flexural behavior of reinforced concrete beams externally strengthened with PET-FRP systems. This material is distinguished by its large rupture strain, leading to an improvement in the ductility of the strengthened structural members compared to conventional FRPs. A three-dimensional (3-D) finite element (FE) model is developed in this study to predict the load-deflection response of a series of experimentally tested beams published in the literature. The numerical model incorporates constitutive material laws and bond-slip behavior between concrete and the strengthening system. Moreover, the validated model was applied in a parametric study to inspect the effect of concrete compressive strength, PET-FRP sheet length, and reinforcing steel bar diameter on the overall performance of concrete beams externally strengthened with PET-FRP.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.253-256
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• 2008

Although researches on the beams strengthened with Fiber reinforced Polymers (FRPs) have recently been conducted around the world, there are few researches on the beams with FRPs under a sustained load. This paper presents the behavior of the beams with Carbon Fiber Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) under a sustained load during 300 days. Strains of steel and FRP reinforcement were measured in order to investigate the behavior of the beams. Additionally, Adjusted Effective Modulus Method (AEMM) and Ghali and Farve's method were used to predict increase in the stress and strain caused by creep and shrinkage. Through the experiment, it was found that the beam with CFRP is more effective than the beam with GFRP in terms of flexural strengthening. Compared with analytical results, it was indicated that strains of tension steels were overestimated, whereas strains of compression steels were underestimated.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.435-444
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• 2005

This paper predicted the shear behavior of reinforced concrete columns using Transformation Angle Truss Model (TATM) considered the effects of bending moment and axial force. Nine columns with various shear span- to-depth ratios and axial force ratios were tested to verify the theoretical results obtained from TATM. Fine linear displacement transducers (LVDT) were attached to a side of the column near the shear critical region to measure the curvature, the longitudinal and transverse axial deformations, and the shear deformation of the column. The test was terminated when the value of the applied load dropped to about $85\%$ of the maximum-recorded load in the post-peak descending branch. All the columns were failed in shear before yielding of the flexural steel. The shear strength and the stiffness of the columns increased, as the axial force increased and the shear span-to-depth ratio decreased. Shear stress-shear strain and shear stress-strain of shear reinforcement curves obtained from TATM were agreed well with the test results in comparison to other truss models (MCFT, RA-STM, and FA-STM).

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.9-12
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• 2008

PSC-I girder is widely used in designing bridge. Currently partial advanced country have constructed bridge with high strength concrete, while in-country rather less concrete strength(40MPa) has been used to build bridge girder. So, this paper presents characteristics and behavior of member casted by high strength concrete to apply practically. For this aim, 4 girders were fabricated to investigate performance and structural behavior. Prior to test, structural analysis was performed with common program. Steel gages and concrete gage were filled up to measure longitudinal and vertical strain of reinforcement and concrete. Linear Variable Differential Transducer and concrete surface gage were also set to measure deflection and strain of concrete. Load-deflection relation and crack mode were analyzed at transfer and test and compared with the structural analysis

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.103-110
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• 2021

Elastomeric bearings composed of flexible rubber materials and steel reinforcement plates are widely used for seismic retrofit of bridges due to their excellent vertical stiffness and flexible lateral stiffness. Especially, it has the advantages of simple construction and low cost. Chloroprene rubber, a type of rubber material, has greater resistance to aging than natural rubber, but its performance is also degraded due to various deterioration factors. Although these aging characteristics are not reflected in the seismic design standards and seismic performance evaluation guidelines, it is reasonable to reflect this when related studies are accumulated. For chloroprene rubber, accelerated heat aging test was performed with variables of heating temperatures and exposure time to analyze shear characteristics. As aging progresses the maximum shear stress and shear strain decrease. Also, the shear stiffness is greatly increased at the same shear strain.

• Advances in concrete construction
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• v.7 no.3
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• pp.151-166
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• 2019

This paper introduces a new efficient analytical method, based on shear deformations obtained with 2D elasticity theory approach, to perform an explicit closed-form solution for calculation the interfacial shear and normal stresses in plated RC beam. The materials of plate, necessary for the reinforcement of the beam, are in general made with fiber reinforced polymers (Carbon or Glass) or steel. The experimental tests showed that at the ends of the plate, high shear and normal stresses are developed, consequently a debonding phenomenon at this position produce a sudden failure of the soffit plate. The interfacial stresses play a significant role in understanding this premature debonding failure of such repaired structures. In order to efficiently model the calculation of the interfacial stresses we have integrated the effect of shear deformations using the equilibrium equations of the elasticity. The approach of this method includes stress-strain and strain-displacement relationships for the adhesive and adherends. The use of the stresses continuity conditions at interfaces between the adhesive and adherents, results pair of second-order and fourth-order coupled ordinary differential equations. The analytical solution for this coupled differential equations give new explicit closed-form solution including shear deformations effects. This new solution is indented for applications of all plated beam. Finally, numerical results obtained with this method are in agreement of the existing solutions and the experimental results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.61-69
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• 2010

Unbonded precast concrete piers have better seismic performances than conventional reinforced concrete piers. In this research, seismic performances of unbonded precast prestressed concrete piers are analyzed using OpenSEES. Main parameters of analysis are concrete strength, jacking force ratio, ratio of tendon, and size of precast segment. In results, as the ratio of tendon and jacking force ratio increase, the flexural strength increases at softening state and ultimate state. Concrete strength and size of precast segment are negligible. But initial jacking force ratio leads to early yielding of prestressing tendon. Since compressive strain in core concrete is much less than ultimate strain, it can be expected that the amount of transverse steel reinforcement is to be reduced in comparison with conventional reinforced concrete column.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2406-2413
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• 2014

Since clear span-to-depth ratio is used to define what is so called a deep beam, it is an important parameter ratio for study about deep beam. Deep beams can be designed by flexure design method, and shear provided by concrete ($v_c$) and by steel ($v_s$) for deep flexure members are provided in ACI 318-99 [1]. But in later version of ACI (from ACI 318-02) it is not provided and deep beams shall be designed either by taking into account nonlinear distribution of strain or by Appendix A of Strut-and-Tie Models (STM). The trend of deep beam design seems to be familiar with strut-and-tie model, but ACI traditional design is not forgotten. By comparing these two method, there should a point which definitely explain the different between the two methods. In this study, 68 samples result of steel, after reinforcement arrangement, are taken to be analyzed.

• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.493-500
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• 2004

In this study, the effects of ring stiffeners for buckling of cylindrical shells with composite materials were analyzed. The finite element method was used: 3-D beam elements were used for stiffeners and flat shell elements were used for cylindrical shells and were improved by introducing a substitute shear strain. The ring stiffeners were of the transverse rib type. The buckling behaviors of the cylindrical shells were analyzed based on various parameters, such as locations and sizes of stiffeners, diameter/length ratios and boundary conditions of shells, and fiber-reinforced angles. Effective reinforcement was examined by understanding the exact behaviors for buckling. The results of the analysis may serve as references for designs and future investigations.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.459-467
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• 2008

This paper describes a proposal for average crack width and immediate deflection calculation in structural concrete members. The model is mathematically derived from actual bond stressslip relationships and tension stiffening effect between reinforcement and the surrounding concrete, and the actual strains of steel and concrete are integrated respectively along the embedded length between the adjacent cracks so as to obtain the difference in the axial elongation. With these, a model for average crack width and immediate deflection in reinforced concrete flexural members are proposed utilizing difference in the axial elongation and average steel strain and moment-curvature relationship with taking account of bond characteristics. The model is applied to the test specimens available in literatures, and the crack width and deflections predicted by the proposal equation in this study are closed to the experimentally measured data compared the current code provisions.