• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.769-774
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• 2000

The purpose of this study was to investigate the structural performance of reinforcement corrosion reinforced concrete beams strengthened with epoxy mortar system. Main test parameters are existence and the magnitude of the reinforcement corrosion and the reinforcing bar and the tensile reinforcement ratio of the specimens. eight beam specimens were tested to investigate the effectiveness of each test variables on maximum load capacity and failure mode. Test results showed that the ultimate moment of th specimens were higher tan the nominal moment and the flexural stiffness was increased about 2.5 times and the cracking moments occurred over 60% of the failure moment in comparison with same sized control beam. However, note that epoxy mortar may conduct member into brittle failure mode.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.691-696
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• 1997

In recent years, stengthening of beam by steel plate, carbon fiber sheets, and carbon fiber laminate is spotlighted in order to repair and rehabilitation of R/C structures. In this study, 3 method of rehabilitation technic are analyzed from the tests. Test parameters are the width of cracks, the method of repair and rehabilitation, the magnitude of existing load. Deflection, failure load, strains of reinforcing bar, strains of sheet and plates are measured during tests. The failure mode and ultimate load are analyzed from these measured data. Test result shows that the width of cracks and the magnitude of existing load do not make any difference of ultimate flexural capacity.

• Journal of the Korea Construction Safety Engineering Association
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• s.49
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• pp.84-91
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• 2009

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.151-158
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• 1998

This paper presents an optimal decision model for minimizing the life-cycle cost of steel box girder bridges. The point is that it takes into account service life process as a whole, and the life-cycle costs include initial (design, testing, and construction) costs, maintenance costs and expected failure costs. The problem is formulated as that of minimization of expected total life-cycle cost with respect to the design variables. The optimal solution identifies those values of the decision variables that result in minimum expected total cost. The performance constraints in the form of flexural failure and shear failure are those specified in the design code. Based on extensive numerical investigations, it may be positively stated that the optimum design of steel box girder bridges based on life-cycle cost approach proposed in this study provides a lot more rational and economical design, and thus the proposed approach will propose the development of new concepts and design methodologies that may have important implications in the next generation performance-based design codes and standards.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.391-394
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• 2005

A theoretical model was developed to predict the shear strength of slender reinforced concrete beams. The shear force applied to a cross-section of the beam was assumed to be resisted primarily by the compressive zone of intact concrete rather than by the tensile zone. The shear capacity of the cross section was defined based on the material failure criteria of concrete: failure controlled by compression and failure controlled by tension. In the evaluation of the shear capacity, interaction with the normal stresses developed by the flexural moment in the cross section was considered. In the proposed strength model, the shear strength of the beam and the location of the critical section were determined at the intersection between the shear capacity and shear demand curves. The proposed strength model was verified by the comparisons to prior experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.71-74
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• 2005

The increasement in the floor hight may be one of the most significant problem in the use of precast concrete double slab in the multi-story buildings. The modified double-tees including duct space at the ends of slab were considered in this study. The length and thickness of nib of modified double tee was increased to receive the uniform reaction from rectangular beam, while the original PCI dapped one to receive the point load from inverted tee beam to the leg of double tee. Shear tests were performed on the ends of the modified double tees which were designed by strut-tie model. The modified double tees generally show more ductile flexural failure in the long thickened nib. It is concluded that they show superior failure patterns than that of original dapped one with shear failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.469-472
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• 2004

This paper presents test results to prevent debonding failure of reinforced concrete beams strengthened with near-surface mounted(NSM) CFRP. Beams strengthened with different strengthening systems with externally bonded CFRP, NSM CFRP and NSM CFRP with mechanical interlocking. Test results indicated that using NSM CFRP is improved the stiffness and increased the flexural capacity of RC beams and NSM CFRP with mechanical interlocking prevented debonding failure of RC beams.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.115-121
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• 2008

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.255-262
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• 2003

In present Korea Highway Bridge Standards the lap splice of longitudinal bars in a potential plastic hinge region is allowed so that large amount of transverse rebar specified in high seismicity regions Is required to prevent brittle bond failure If the brittle failure effects can be completely removed from the conventional designed piers, the amount of transverse rebar will be reduced drastically. In this study scaled models with solid and hollow rectangular sections were tested to investigate the seismic behavior of RC piers with 50％ of lap-spliced longitudinal bars in plastic hinge regions. In the tests the typical flexural failure conducting a ductile behavior were observed in both models. It is shown that the 50％ of lap-spliced bars can be considered as a good alternative of seismic detailing for longitudinal bars.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.545-556
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• 2021

The present experimental study evaluated the seismic performance of six engineered cementitious composite (ECC) columns strengthened with carbon fiber reinforced polymer (CFRP) laminates under cyclic lateral loading. The ECC columns damaged and crushed in the first stage of cyclic tests were repaired using the ECC with a certain polyvinyl alcohol (PVA) fiber and strengthened with flexural and sheer CFRP laminates and then re-assessed under the cyclic loading. The effects of some variables were examined on lateral displacement, energy absorption and dissipation, failure modes, crack patterns, load bearing capacity and plasticity, and the obtained results were compared with those of the first stage of cyclic tests. The results showed that retrofitting the ECC columns can improve their performance, plasticity and load-bearing threshold, delayed the concrete failure, changed the failure modes and increased the energy absorbed by the strengthened columns element by over 50%.