• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.88-91
• /
• 2004

It is generally known that the bonding strength of RC(Reinforced Concrete) flexural members strengthened by fiber sheet composites are sufficient and the bonding failure does not occur until the sheet failed. However, many researchers have been reported that, before the failure of the sheet, the bonding failure happens even though the bonding length is sufficient. This study was carried out to evaluate the effectiveness of shear key and U strip on flexural behavior of reinforced concrete beam structures. The ply number of CFS(Carbon Fiber Sheet), location of shear key, and existence or not of U strip were selected as the main test variables. Test results show that the behavior of a beam of which shear key is located in the nearby. of support and U strip is not existent, and having CFS of 1 ply is mostly improved.

• Structural Engineering and Mechanics
• /
• v.45 no.4
• /
• pp.455-470
• /
• 2013

RC flat plates that have no flexural stiffness by boundary beams may be governed by a serviceability as well as a strength condition. A construction sequence and its impact on the distributions of construction loads among slabs tied by shores are decisive factors influencing immediate and long term performances of flat plate. Over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction. A reshoring work may be helpful in reducing slab deflections by controlling the vertical distributions of construction loads in a multi-shored flat plate system. In this study, a change of construction loads by reshoring works and its effects on deflections of flat plate systems under construction are analyzed. The slab construction loads with various reshoring schemes are defined by a simplified method, and the practical calculation of slab deflections with considering construction sequences and concrete cracking effects is applied. From parametric studies, the reshoring works are verified to reduce construction loads and slab deflections.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.561-566
• /
• 1999

Due to recent demolition works of aged concrete bridges and buildings, a considerable amount of waste concrete material have been reclaimed without crushing works. It is well believed that waste concrete could be used for recycling good coarse aggregate, which could contribute to partly reduce environmental pollutions due to noise and dust by demolition works, and also to solve the shortage of natural aggregate for new concrete works. This experimental study is to investigate the flexural and shear behaviour of recycling RC beams with pertinent amount of recycling coarse aggregate, such as 30%, 50% and 100% of total aggregate volume. It is concluded from the test that structural behaviour of recycled concrete is determined to have similar behaviour of normal concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10a
• /
• pp.517-522
• /
• 2000

In the past few years, the nondestructive inspection technology has greatly developed due to the increased necessity to gain a complete understanding of the bridge behavior. Especially, the deformations of bridges contain a lot of informations about its health state. By measuring these deformations it is possible to analyze the loading and aging behavior of the structure. However, the current methods (such as LVDT, dial gage, optical displacement tranceducer, etc) are often of changeable application on site and have the limitations of installation. In this paper, the classical beam theory was reviewed and the deflections of structure are estimated using measured strain which is easy to acquire. The applicability of this algorithm is verified by a preliminary steel beam test and two types of concrete beam tests. Also fiber optic sensors as well as resistive strain gages were installed in the concrete beams to establish the applicability of fiber optic sensors in the field of civil engineering.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.505-506
• /
• 2009

This paper is an investigation of the fatigue behaviors on the GFRP bar and GSP embedded method as repair and reinforced method. In the experiments, the stress ratio R is 0.1 and loading frequency is 1.5 Hz. As a result of fatigue test, the fatigue strengths of the GFRP bar and GSP reinforced beams were 58%, 52% of the static strength in S-N curve.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.425-426
• /
• 2010

The cracking characteristics of high flowing self-compacting concrete(HSCC) and conventional concrete(CC) was investigated. HSCC shows high crack resistance compare to CC due to self compacting properites.

• Computers and Concrete
• /
• v.22 no.1
• /
• pp.11-25
• /
• 2018

A numerical approach for the evaluation of the flexural response of Steel Fibrous Concrete (SFC) cross-sections with arbitrary geometry, with or without conventional steel longitudinal reinforcing bars is proposed. Resisting bending moment versus curvature curves are calculated using verified non-linear constitutive stress-strain relationships for the SFC under compression and tension which include post-peak and post-cracking softening parts. A new compressive stress-strain model for SFC is employed that has been derived from test data of 125 stress-strain curves and 257 strength values providing the overall compressive behaviour of various SFC mixtures. The proposed sectional analysis is verified using existing experimental data of 42 SFC beams, and it predicts the flexural capacity and the curvature ductility of SFC members reasonably well. The developed approach also provides rational and more accurate compressive and tensile stress-strain curves along with bending moment versus curvature curves with regards to the predictions of relevant existing models.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1999.10a
• /
• pp.19-26
• /
• 1999

This paper describes an analytical study on nonlinear hysteretic behavior of hybrid steel beam with reinforced concrete ends. Two types of analytical model, Polygonal Model[PM] and Hybrid Model[HM], were used to represent the nonlinear hysteretic behavior PM used three parameters, HM used an additional parameter to consider the initial stiffness reduction. The parameters calibrated comparing the hysteretic performance obtained from experiments. The purpose of this study is to develop an analytical model which can take into account the initial stiffness reduction of the hybrid members and to represent exactly the hysteretic performance for the hybrid structures with RC and steel. The analytical study showed PM tends to overestimate initial stiffness and strength. However, HM which is capable to consider the initial stiffness reduction gave good prediction on initial stiffness, post-yielding performance, strength, pinching response and so on.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.10a
• /
• pp.501-507
• /
• 1996

The final objectives of this study are to present the theoretical formula for reasonable structural analysis and practical codes on the repair/strengthening of damaged reinforced concrete structrues. For that purpose, in last year, preliminary experiments for flexure and shear of beam structure using carbon sheet and steel plate were performed, and in sequence, in this year, using aramid fiber sheet and steel plate more extensive experiment were performed. Repair for the performance of flexure and shear was focused on, and main variables were selected considering aplicablilty for practical field, such as, spacing of anchor bolt, lapping, jacking up, preloading level, and fiber difection as well as length of repairing plate and thickness. so new results from various angles are to be presented.

• 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.