• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.475-482
• /
• 1997

This study reports the results of flexural test on 6 specimens for maximum reinforcement ratio and 4 specimens for minmum reinforcement ratio with concrete compressive strength 1,000, 1,200 kg/$\textrm{cm}^2$ . The major test variables for the reinforcement ratio designed 0.55$\rho_b$, 0.65$\rho_b$, 0.75$\rho_b$ for maximurm reinforcement ratio test 14/fy $\sqrt[0.72]{\rho}\acute{f}_c$ / $f_y$ for minimum reinforcement ratio test. The test results were compared with ACI 318-95 Code. In the Ultra High Strength Concrete beam, the maximum reinforcement ration should be less than 0.6$\rho_b$ for ductile behavior and the existing minimum reinforcement ratio by ACI Building Code is Sufficiently safe.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.227-230
• /
• 2005

This paper provides a method to predict the ductile capacity of reinforced concrete beam-column joints that fail in shear after the plastic hinges occur at both ends of the adjacent beams. The proposed method takes into account shear strength deterioration in the beam-column joints. The shear strength and the corresponding ductility of the proposed method was verified by comparing with the four RC beam-column assembles under reversed cyclic loading corrected from the technical literature. Comparisons between the observed and calculated shear strengths and their corresponding ductilities of the tested assembles, showed reasonable agreement

• Journal of Ocean Engineering and Technology
• /
• v.14 no.1
• /
• pp.52-59
• /
• 2000

Flexural fracture characteristics of newly-developed Grid-type carbon fiber plastics in the deteriorated reinforced concrete structures were investigated by the four-points fracture test to verify the strengthening effects in the beam specimens. Results showed that initial cracks appeared in the boundary layers of fibers embedded in the newly-placed mortar concrete slowly progressed to the direction of supports and showed fracture of fiber plastics and brittle failure of concrete in compression in sequence after the yielding of steel reinforcement. Accordingly the reasonable area of Grid-type carbon-fiber plastics in the strengthening design of deteriorated RC structures should be limited and given based on the ultimate strength design method to avoid the brittle failure of concrete structures.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2000.10a
• /
• pp.190-197
• /
• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Steel and Composite Structures
• /
• v.17 no.6
• /
• pp.777-790
• /
• 2014

The purpose of this study is to investigate the seismic performance of reinforced concrete (RC) frames strengthened by profiled steel sheet bracing which takes the influence of infill walls into consideration. One-bay, two-story, 1/3 scale two specimens shared same feature of dimensions, one specimen consists only beams and columns; the other one is reinforced by profiled steel sheet bracing with infill walls. Hysteretic curves, envelope curves, stiffness degradation curves and energy dissipation capacities are presented based on test data. Test results indicate that the ultimate load of strengthened specimen has been improved by 225%. The stiffness of reinforced by profiled steel sheet bracing has been increased by 108%. This demonstrates that infill walls and profiled steel sheet bracing enhanced the strength and stiffness distinctly. Energy dissipation has an obvious increase after 12 cycles. This shows that the reinforced specimen is able to bear the lateral load effectively and absorb lots of seismic energy.

• Structural Engineering and Mechanics
• /
• v.62 no.4
• /
• pp.477-485
• /
• 2017

The structural designs of RC flat plates that have no flexural stiffness by boundary beams may be governed not by strength conditions but by serviceabilities. Specially, since over-loading and tensile cracking in early-aged slabs significantly increase the short- and long-term deflections of a flat plate system, a construction sequence and its impact on the slab deflections may be decisive factors in designs of flat plate systems. In this study, the procedure of simulating slab deflections with considering construction sequences, concrete cracking, and long-term effects is proposed. The proposed method is practically useful, as it can predict well the slab deflections at construction and service stages only with a few input data. The proposed method is verified by comparisons with measured results in a real-scale test.

• Structural Engineering and Mechanics
• /
• v.41 no.5
• /
• pp.645-662
• /
• 2012

Deteriorative effects of steel corrosion on the structural response of reinforced concrete are simulated for varying degrees of corrosion. The simulation approach is based on a three-dimensional irregular lattice model of the bulk concrete, in which fracture is modeled using a crack band approach that conserves fracture energy. Frame elements and bond link elements represent the reinforcing steel and its interface with the concrete, respectively. Polylinear stress-slip properties of the link elements are determined, for several degrees of corrosion, through comparisons with direct pullout tests reported in the literature. The link properties are then used for the lattice modeling of reinforced concrete beams with similar degrees of corrosion of the main reinforcing steel. The model is successful in simulating several important effects of steel corrosion, including increased deflections, changes in flexural cracking behavior, and reduced yield load of the beam specimens.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.6
• /
• pp.157-164
• /
• 1997

최근 손상된 구조물에 탄소섬유쉬트 보강공법이 많이 사용되고 있다. 탄소섬유쉬트 보강에 따른 휨내력의 증진이 이루어지기 위해서는 보와 탄소섬유쉬트의 일체거동이 이루어져야 하며, 쉬트단부에서 부착파괴가 발생하지 않아야 한다. 따라서 이번 실험에서는 탄소섬유쉬트의 보강매수에 따른 부착파괴의 거동을 살펴보았다. 전시험체에서 부착파괴가 발생하였으며 부착파괴가 발생한 하중의 크기는 보강매수에 관계없이 비슷하였다. 부착파괴의 거동은 순수부착파괴와 피복박리파괴로 구분될 수 있었으며 부착응력은 단부에서 집중현상이 나타났고 집중된 응력의 크기는 15.39~41.42kg/$\textrm{cm}^2$로 나타났다. 정착길이내의 평균부착응력은 6.85~8.99kg/$\textrm{cm}^2$으로서 평균 7.38kg/$\textrm{cm}^2$이고 이 값은 이론치인 6.19kg/$\textrm{cm}^2$보다 약간 높으며 설계부착응력인 6kg/$\textrm{cm}^2$에 부합되는 것으로 나타났다. 따라서 설계부착응력 6kg/$\textrm{cm}^2$은 정착길이의 설계시 합리적 값으로 평가되었다.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.57-60
• /
• 2004

Recently, Many researchers are interested in ultra-high performance cementitious compostie characterized by high strength and high durability and trying to apply for structural members. In this paper, twelves fiber-reinforced UHPCC with high compressive strength over 150MPa I shaped beam without stirrups were tested under various conditicns to investigate the mechanical behavior of UHPCC I shaped beam without stirrups. Variables considered in this study includes steel fiber volume fraction, reinforcememt steel ratio, and shear spar ratio.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.145-148
• /
• 2006

Near surface mounted (NSM) is a recent strengthening technique based on bonding fiber reinforced polymer (CFRP) bars (rods and laminate strips), the use of NSM FRP bars is Emerging as a promising technology for increasing flexural strength of deficient concrete. In order for this technique to perform effectively, the structural behaviour of RC element strengthened with NSM FRP bars to be fully characterized. Totally, 10 beams were tested using symmetrical two-point loads test. The parameters examined under the beam test were a diffrent type of strengthening length.