• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.218-221
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• 2006

The past Korean Bridge Design Specifications have no limitation on the amount of lap splices of longitudinal bars in the plastic hinge zone of piers. A majority of bridge piers which have been non-seismically designed might have some lap splices in plastic hinge zone. Also a number of those piers in Korea have a low aspect ratio(height/section area). So, some problems such as low ductility behavior may happen. In this study, the real pier which was non-seismically designed and has a low aspect ratio was selected for the quasi-static tests. Two groups of full scaled RC pier models of which aspect ratios are about 2.26 and about 2.67 were fabricated. And then, quasi-static tests according to the drift level history method were implemented. From the test results, the failure of these test specimens have been shown in the complex shear-flexural or shear modes. The low aspect ratio and the lap splice have largely influenced on the seismic performance of bridge piers.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.453-456
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• 2003

This research is to evaluate the seismic performance of reinforced concrete bridge piers with lap-spliced longitudinal reinforcement steels in the plastic hinge region, and to develop the enhancement scheme of their seismic capacity. Six circular columns of 0.6m diameter and 1.5m height were made with two confinement steel ratios. They were damaged under series of artificial earthquakes that could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under an axial load, P=$0.1f_{ck}A_{g}$, and residual seismic performance of damaged columns was evaluated. Test results show that RC bridge piers with lap-spliced longitudinal steels behaved with minor damage even under artificial earthquakes with 0.22g PGA, but failed at low ductility subjected to the subsequent quasi-static load test. This failure was due to the debonding of the lap splice. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region showed significant improvement both in flexural strength and displacement ductility.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.635-638
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• 2003

This paper deals with structural behavior of reinforced concrete beams with high strength under fire and fire damaged condition. The main purpose of this study is to evaluate the residual strength of flexural members by exposure time to fire. For this purpose, six beam specimens are fabricated and experimented. Among the specimens, four specimens are exposed to the fire for 60 and 90 minutes and two specimens are control beam that is not exposed to fire. After being cooled in room temperature, the specimens are loaded to the failure. The research result shows that the main variables of the test, concrete cover and exposure time to fire are much influenced on the structural behavior and the residual strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.111-112
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• 2010

This study proposes a new methodology of earthquake damage evaluation for R/C Buildings combined with shear and flexural failure systems, based on non-linear required strength spectrum. Part I shows a concept of methodology of earthquake damage evaluation, which is estimated on the basis of system ductility, non-linear required strength spectrum and remaining seismic capacity ratio.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.27-31
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• 2001

Hi-Nicalon SiC fiber reinforced SiC composites (SiC/SiC) have been fabricated by the reaction sintering process. Braided Hi-Nicalon SiC fiber with double interphases of BN and SiC was used in this composite system. The microstructures and the mechanical properties of reaction sintered SiC/SiC composites were investigated through means of electron microscopies (SEM, TEM, EDS) and bending tests. The matrix morphology of reaction sintered SiC/SiC composites was composed of the SiC phases that the composition of the silicon and the carbon is different. The TEM analysis showed that the residual silicon and the unreacted carbon were finely distributed in the matrix region of reaction sintered SiC/SiC composites. Reaction sintered SiC/SiC composites also represented proper flexural strength and fracture energy, accompanying the noncatastrophic failure behavior.

• Steel and Composite Structures
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• v.5 no.1
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• pp.49-70
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• 2005

This paper reports on finite element analysis techniques that may be applied to the study of circular hollow structural sections and related bearing connection geometries. Specifically, a connection detail involving curved steel saddle bearings and a Structural Tee (ST) connected directly to a large-diameter Hollow Structural Section (HSS) truss chord, near its open end, is considered. The modeling is carried out using experimentally verified techniques. It is determined that the primary mechanism of failure involves a flexural collapse of the HSS chord through plastification of the chord wall into a well-defined yield line mechanism; a limit state for which a shell-based finite element model is well-suited to capture. It is also found that classical metal plasticity material models may be somewhat limited in their applicability to steels in fabricated tubular members.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.715-720
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• 1997

In this study, the behavior of R/C beam strengthened with carbon fiber laminate(C.F.L) is analyzed from the test results. Test parameters ar the width and the thickness of C.F.L. The failure mode and ultimate load are analyzed from these measured data. Test results shows that the peak load of specimens strengthened with C.F.L. is increased to 1.27~2.04 times of that of non-rehabilitation specimen. The wider lap width, large amount of rehabilitation materials, the larger strength is obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.287-292
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• 2003

The large-scale direct tension tests of plain concrete were performed and then the complete load-CMOD(crack mouth opening displacement) curves with a stable postpeak descending part were presented. Two independently controlled actuators were used to ensure a homogeneous increasing of CMOD in both notches of a specimen and to avoid secondary flexural stresses. It was compared the fracture energies from the test results with them from a classical prediction equation by Bazant and Oh (983), The results are indicated that the fracture energies from these large-scale direct tensile tests are large as 1.5-2 times on average against them from the Bazants prediction equation. But the tensile strength for large-size specimens was about half of the values determined from the splitting tensile strength tests for 10 by 20mm cylindrical specimens due to size effect.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.549-554
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• 2003

In order to overcome the brittle failure of strengthening with FRP-rebars inherent to their brittle properties, two approaches have been attempted. One is to improve the properties like ductile Hybrid FRP Rods, and the other is to develop a ductile strengthening with partially unbonded FRP rebars. Experiments on real size specimen were performed to evaluate the performance of NSM (Near Surface Mounted Strengthening) and SIM (Section Increment Methods) with FRP rebars. This paper discusses the results of the tests on 8 slab specimen in terms of flexural resistance, ductility, and fatigue. They show that NSM or S1M with FRP rebars are very effective measures to strengthen existing RC structures. Above all, strengthening with partially unbonded ductile Hybrid FRP Rods shows sufficient ductility similar to that of properly designed RC structures.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.4
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• pp.29-36
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• 2009

This is a basic experimental study to apply FRP modular box member to a variety of construction structures exposed to flexural strength, such as a slab and a girder. Applying FRP modular box member to a real structure requires a large section. FRP box member was made into modular systems. Tests were conducted under various conditions in order to analyze jointing performance of the developed FRP modular box member as a large section. For the methods of jointing FRP modular box member, synthetic resins connection, mechanical connection, and a combination of both were used to test both length and breadth connection. As a result of the test, using urethane + two bolts + sheets was the most efficient method of connecting FRP modular box member. It is expected that the proposed joint system in this study will contribute to the increase of failure load and synthesis behavior of FRP modular box member.