• Magazine of the Korea Concrete Institute
• /
• v.6 no.4
• /
• pp.161-168
• /
• 1994

Half-P.C. slab system is the composite structural system which utilizes precast concrete for lower portion and cast in situ concrete for upper portion slab. When the composite slab using Half P.C. slab is deformed by flexural moment, horizontal shear happened at the interface between Half P.C. slab and topping concrete. To resist horizontal shear strength a scratch method has tried. To determine ultimate interface shear strength, shear stress, and shear coefficient, high and normal strength concrete are used for topping concrete. Major variables are compressive strength of topping concrete with or without shear reinforcement, quantitative roughness of the P.C. :surface and tie or untie of the stud with welded deformed wire fabric in the P.C. member. The Icross sectional area on joints is 3,200 $cm^2$ in all specimens. Test results showed that shear stress increased, as the depth of the quantitative roughness increased. The horizontal shear strength could be resisted with safe by the quantitative roughness without shear tie. A shear coefficient determinant equation is proposed such that K = 0.025918 + 0.0068894$\cdot$R – 0.000182354${\cdot}R^2$

• The Journal of Engineering Geology
• /
• v.31 no.4
• /
• pp.561-577
• /
• 2021

The ten standard roughness profiles suggested by Barton and Choubey (1977) were extended to make three-dimensional (3D) joint models whose profiles were identical at any cross section. Replicas of joint models were produced using plaster of Paris, and direct shear tests were performed to verify the joint roughness coefficients (JRC) of the standard roughness profiles. Joint shear strengths measured by direct shear tests were compared with those predicted by the shear failure criterion suggested by Barton (1973) based on JRC, joint compressive strength (JCS), and joint basic friction angle (𝜙_b). Shear strengths measured from joints of the first and fourth standard roughness profiles were close to predicted values; however, shear strengths measured from the other joint models were lower than predicted, the differences increasing as the roughness of joints increased. Back calculated values for JRC, JCS, and from the results of the direct shear tests show measured shear strengths were lower than predicted shear strengths because of the JRC values. New JRC were back calculated from the measured shear strength and named JRC_m. Values of JRC_m were lower than the JRC for the standard roughness profiles but show a strong linear relationship to JRC. Corrected JRC_m values for the standard roughness profiles are provided and revised relationships between JRC_m and JRC, and new shear strength criterion are suggested.

• Structural Engineering and Mechanics
• /
• v.86 no.3
• /
• pp.385-397
• /
• 2023

This study presents an experiment and analysis to compare the seismic behavior of full-scale reinforced concrete beam-column joint strengthened by prestressed steel strips, externally bonded steel plate, and CFRP sheets. For experimental investigation, five specimens, including one joint without any retrofitting, one joint retrofitted by externally bonded steel plate, one joint retrofitted by CFRP sheets, and two joints retrofitted by prestressed steel strips, were tested under cyclic-reserve loading. The failure mode, strain response, shear deformation, hysteresis behavior, energy dissipation capacity, stiffness degradation and damage indexes of all specimens were analyzed according to experimental study. It was found that prestressed steel strips, steel plate and CFRP sheets improved shear resistance, energy dissipation capacity, stiffness degradation behavior and reduced the shear deformation of the joint core area, as well as changed the failure pattern of the specimen, which led to the failure mode changed from the combination of flexural failure of beams and shear failure of joints core to the flexural failure of beams. In addition, the beam-column joint retrofitted by steel plate exhibited a high bearing capacity, energy consumption capacity and low damage index compared with the joint strengthened by prestressed steel strip, and the prestressed steel strips reinforced joint showed a high strength, energy dissipation capacity and low shear deformation, stirrups strains and damage index compared to the CFRP reinforced joint, which indicated that the frame joints strengthened with steel plate exhibited the most excellent seismic behavior, followed by the prestressed steel strips.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.15-16
• /
• 2022

This study is to confirm the integration performance of joints according to the method of applying the super retarding agent. When the super-delay system was applied, the integration performance was found to decrease somewhat on the 7th day of age. In the case of the 28th of age, it was found that the integration performance is improved. When a diluent is injected and a super delay agent is sprayed, shear bond strength is the highest.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.639-642
• /
• 2004

Lately outmoded and functionally obsolete buildings are often remodelled and restored. When existing reinforced concrete(RC) apartments are remodelled, one of main reasons of the remodelling is to expand dwelling space. The experimental or theoretical research on plane expansion of RC apartments is quite scare. In this research, 9 RC slabs connected by hinged joints were tested. The test results indicated that the shear strength of the RC test slabs having various types of dowel bars was about twice that calculated by the ACI 318-02 code.

• Steel and Composite Structures
• /
• v.3 no.5
• /
• pp.321-331
• /
• 2003

The paper presents the results of an experimental investigation conducted on welded tubular joints, that are employed in offshore platforms, to study the behaviour and strength of these joints under axial brace compression loading. The geometrical configuration of the joints tested were T and Y. The nominal diameter of the chord and brace members of the joint were 324 and 219 mm respectively. The chord thickness was 12 mm and the brace 8 mm. The tested joints are approximately quarter size when compared to the largest joints in the platforms built in a shallow water depth of 80 m in the Bombay High field. Some of the joints were actually fabricated by a leading offshore agency which firm is directly involved in the fabrication of prototype structures. Strength of the internally ring-stiffened joints was found to be almost twice that of the unstiffened joints of the same configuration and dimensions. Bending of the chord as a whole was observed to be the predominant mode of deformation of the internally ring-stiffened joints in contrast to ovaling and punching shear of the unstiffened joints. It was observed in this investigation that unstiffened joint was stiffer in ovaling mode than in bending and that midspan deflection of unstiffened joint was insignificant when compared to that of the internally ring stiffened joint. The measured midspan deflection of the unstiffened joint in this investigation and its relation with the applied axial load compares very well with that predicted for the brace axial displacement by energy method published in the literature. A comparison of the measured deflection and ovaling of the unstiffened joint was made with that published by the author elsewhere in which numerical prediction of both quantities have been made using ANSYS software package. The agreement was found to be quite good.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.10a
• /
• pp.81-82
• /
• 2016

The present study aims to derive optimal interface treatment conditions for emulating a monolithic construction. The joints in this construction are formed through the bonding shear evaluation method during the placement of ultra-high-performance concrete (UHPC) and normal strength concrete (NSC). The evaluation items include push-off tests for homogeneous UHPC + UHPC and heterogeneous NSC + UHPC. The experimental samples comprised a monolithic placement as the baseline, two levels for the separated placement according to the compression strength of concrete, and five levels for the interface treatment. The increase in the number of grooves and their cross-sectional areas only slightly influenced the bonding shear performance. The optimal interface treatment method for the homogeneous UHPC + UHPC construction grooves was at least 30mm. The heterogeneous NSC + UHPC construction should utilize waterjet roughening to expose the aggregate for the increased roughness.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.561-566
• /
• 2001

Load at steel beam column joints transfered by beam depend on bond strength between concrete and steel tube. But it is different to transmit a load efficiently in the established concrete filled steel tubular column. Therefore, shear-connector is demanded for transfering loads efficiently. An ascent of bond stress and a transmission of load after debonding are expected by a reinforcement of shear-connector

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.106-112
• /
• 2017

This paper presents a mathematical model derived from the upper-bound theorem of concrete plasticity to rationally evaluate the shear friction strength of concrete interfaces with a construction joint. The upper limit of the shear friction strength was formulated from the limit state of concrete crushing failure on the strut-and-tie action along the construction joints to avoid overestimating the shear transfer capacity of a transverse reinforcement with a high clamping force. The present model approach proposed that the cohesion and coefficient of friction of concrete can be set to be $0.27(f_{ck})^{0.65}$ and 0.95, respectively, for rough construction joints and $0.11(f_{ck})^{0.65}$ and 0.64, respectively, for smooth ones, where $f_{ck}$ is the compressive strength of concrete. From the comparisons with 155 data compiled from the available literature, the proposed model gave lower values of standard deviation and coefficient of variation of the ratios between predictions and experiments than AASHTO and fib 2010 equations, indicating that the proposed model has consistent trends with test results, unlike the significant underestimation results of such code equations in evaluating the shear friction strength.

• Steel and Composite Structures
• /
• v.19 no.6
• /
• pp.1561-1580
• /
• 2015

No significant improvement has been observed on the seismic performance of the ordinary steel reinforced concrete (SRC) columns compared with the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type section steel were put forward on this background: a cross-shaped steel whose flanges are in contact with concrete cover by extending the geometry of webs, and a rotated cross-shaped steel whose webs coincide with diagonal line of the column's section. The advantages of new-type SRC columns have been proved theoretically and experimentally, while construction measures and seismic behavior remain unclear when the new-type columns are joined onto SRC beams. Seismic behavior of SRC joints with new-type section steel were experimentally investigated by testing 5 specimens subjected to low reversed cyclic loading, mainly including the failure patterns, hysteretic loops, skeleton curves, energy dissipation capacity, strength and stiffness degradation and ductility. Effects of steel shape, load angel and construction measures on seismic behavior of joints were also analyzed. The test results indicate that the new-type joints display shear failure pattern under seismic loading, and steel and concrete of core region could bear larger load and tend to be stable although the specimens are close to failure. The hysteretic curves of new-type joints are plumper whose equivalent viscous damping coefficients and ductility factors are over 0.38 and 3.2 respectively, and this illustrates the energy dissipation capacity and deformation ability of new-type SRC joints are better than that of ordinary ones with shear failure. Bearing capacity and ductility of new-type joints are superior when the diagonal cross-shaped steel is contained and beams are orthogonal to columns, and the two construction measures proposed have little effect on the seismic behavior of joints.