• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2020.11a
• /
• pp.190-191
• /
• 2020

The bonding of steel bar to concrete is closely related to the roughness and corrosion degree of steel bar surface. The accelerated corrosion of concrete specimens with different reinforcement diameters was carried out in this test. Through the pullout test of the corroded concrete specimens, the relationship between the bond stress and the displacement of the corroded concrete specimens under the corresponding corrosion degree was obtained. The bond stress of reinforced concrete with different size and corrosion degree are compared and analyzed to find out the influence of corrosion on the bonding property of reinforced concrete.

• Structural Engineering and Mechanics
• /
• v.91 no.3
• /
• pp.239-250
• /
• 2024

With the aim to provide better predication about fracture behavior, a numerical simulating strategy based on the rigid spring model is proposed for reinforced concrete (RC) structures in this study. According to the proposed strategy, concrete is partitioned into a series of irregular rigid blocks based on the Voronoi diagram, which are connected by interface springs. Steel bars are simulated by bar elements, and the bond slip element is defined at bar element nodes to describe the interaction between reinforcement and concrete. A concrete damage evolution model based on the separation criterion is adopted to describe the weakening process of interface spring between adjacent blocks, while a nonlinear bond slip model is introduced to simulate the synergy behaviour of reinforced steel bars and concrete. In the damage evolution model of concrete, the influence of compressive stress perpendicular to the interface on the shear strength is considered. To check the effectiveness and applicability of the proposed modelling, experimental and numerical studies about a simply-supported RC beam and the two-notched concrete plates in Nooru-Mohamed's experiment are conducted, and the grid sensitivity are investigated.

• Structural Engineering and Mechanics
• /
• v.65 no.2
• /
• pp.155-162
• /
• 2018

A smart glass fiber reinforced polymer (SMFRP) reinforcing bar with a fiber Bragg grating (FBG) sensor was fabricated using a pultrusion technique, while ribs were formed to improve bonding between concrete and SMFRP. Then, strain of SMFRP bars were measured for a uniaxial tension test of an SMFRP bar, and a four-point bending test of concrete beams reinforced with SMFRP bars. The results of a uniaxial tension test illustrate that the strain obtained from an FBG sensor agrees well with that obtained from electrical resistance strain gauge (ERSG). Additionally, concrete beams reinforced with SMFRP bars were fabricated, and actual flexural test were performed while the strain of with an FBG sensor was compared with that of ERSG. The experimental results demonstrate that SMFRP bars can be used as reinforcement of concrete member while providing deformation information. Furthermore, SMFRP bars may provide stronger durability and smart monitoring to reinforced concrete members under corrosive environments during a service life.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.361-364
• /
• 2008

This study was performed to estimate the anchorage behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Therefore, the steel bar and the steel tendon must be unified in both ends and compressive and tensile force be offset. Anchorage dimension of 6 test specimens was designed under PTI specification which defined maximum stress and deformation to estimate structural behavior. Test results showed that the stress and the deformation of anchorage were within limits if the steel bar behaviored elastically.

• Smart Structures and Systems
• /
• v.16 no.1
• /
• pp.67-79
• /
• 2015

Acoustic emission analysis is an effective technique for monitoring the evolution of damage in a structure. An experimental analysis on a set of reinforced concrete beams under flexural loading was carried out. A mixed AE analysis method which used both parameter-based and signal-based techniques was presented to characterize and identify different failure mechanisms of damage, where the signal-based analysis was performed by using the Hilbert-Huang transform. The maximum instantaneous energy of typical damage events and the corresponding frequency characteristics were established, which provided a quantitative assessment of reinforced concrete beam using AE technique. In the bending tests, a "pitch-catch" system was mounted on a steel bar to assess bonding state of the steel bar in concrete. To better understand the AE behavior of bond-slip damage between steel bar and concrete, a special bond-slip test called pullout test was also performed. The results provided the basis of quantitative AE to identify both failure mechanisms and level of damages of civil engineering structures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.147-148
• /
• 2009

The anchorage system unified both PS strand and bar effectively introduced a prestress into a flexural concrete members. This study examined the relation between the anchorages of both ends and the introduced force and derived the equation for design.

• Journal of the Korea Concrete Institute
• /
• v.23 no.4
• /
• pp.471-478
• /
• 2011

For a practical simplicity in designing of reinforced concrete structures, the indirect crack controlling method of limiting bar spacing is adopted in KCI structural design provisions. In addition, a direct method for evaluating crack width is also provided in the appendix of the code. But there may be some mismatched results between these two crack controlling methods. In this study, limit values of maximum bar spacing calculated from KCI provisions, KCI appendix, and Frosch's equation are examined as concrete strength, cross-section height, and concrete cover are varied, and the differences are analyzed. From the results, it becomes clear that the differences between maximum bar spacing calculated from KCI code text provisions and those from KCI code appendix provisions are too significant to be neglected. Therefore, rational crack models are suggested in order to get rid of the discrepancy between the direct and indirect control methods.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.1
• /
• pp.117-125
• /
• 1995

Bond test was carried out to assess the effect of several variables on bond characteristics between reinforcing bar and concrete. Key variables are concrete compressive strength($f_c$'=340, 460, 6513, 904kg/$cm^2$), concrete cover (25, 38, 51, 105, IlOmm), and bar diameter(Dl3 and D22). Confining effect and bar spacing are not taken into account. Thirty-two specimens subjected to uniaxial tension were tested under hypothesis uniform bond stress distribution along the reinforcing bar embeded in concrete. Failure mode was examined and local bond stress versus slip relationship diagrams were represented to show effect of the above variables, also test results(u1timate bond stress) were compared with bond and development provisions of the ACI Building Code(AC1 318-89) and proposed equations from previous research. According to analysis, borld stress and ultimate bond stress increased although compressive strength increased beyond the ACI Building Code upper limit. Therefore in calculating development length. compressive strength effect(exceeding 700kg /$cm^2$) should be accounted.

• Structural Engineering and Mechanics
• /
• v.32 no.2
• /
• pp.251-267
• /
• 2009

Reinforced concrete (RC) structures consist of two different materials: concrete and steel bar. The stress transfer behaviour between the two materials through bond plays an important role in the load-carrying capacity of RC structures, especially when they subject to lateral load such as blast and seismic load. Therefore, bond and slip between concrete and reinforcement bar will affect the response of RC structures under such loads. However, in most numerical analyses of blast-induced structural responses, the perfect bond between concrete and steel bar is often assumed. The main reason is that it is very difficult to model bond slip in the commercial finite element software, especially in hydrodynamic codes. In the present study, a one-dimensional slide line contact model in LS-DYNA for modeling sliding of rebar along a string of concrete nodes is creatively used to model the bond slip between concrete and steel bars in RC structures. In order to model the bond slip accurately, a new approach to define the parameters of the one-dimensional slide line model from common pullout test data is proposed. Reliability and accuracy of the proposed approach and the one-dimensional slide line in modelling the bond slip between concrete and steel bar are demonstrated through comparison of numerical results and experimental data. A case study is then carried out to investigate the bond slip effect on numerical analysis of blast-induced responses of a RC column. Parametric studies are also conducted to investigate the effect of bond shear modulus, maximum elastic slip strain, and damage curve exponential coefficient on blast-induced response of RC columns. Finally, recommendations are given for modelling the bond slip in numerical analysis of blast-induced responses of RC columns.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1A
• /
• pp.155-163
• /
• 2008

On the construction site with trends of large scale, high rise and specialization, testing construction of high performance concrete, superior to conventional concrete, is continued to increase. For bridge construction, application of full staging method is gradually decreasing due to noise, dust, and prolonged construction period. Recently, precast construction, which is optimized to urban environment and shorter work period, gains popularity significantly. In bridge structure, overcrowding arrangement of bar is used to ensure its safety. For the manufacturing of overcrowding arrangement of bar, High flowing self-compacting concrete, which is superior to conventional concrete in flowability and compacting property, should be implemented. In this study, the application of blast-furnace slag and fly ash to binary and ternary blended system on the High flowing self-compacting concrete for bridge structure with overcrowding arrangement of bar is evaluated by flowability in accordance with the first class regulations of Japan Society of Civil Engineering (JSCE).