• Structural Engineering and Mechanics
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• v.60 no.2
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• pp.301-312
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• 2016

In a concrete member under pure tension, the stress in concrete is uniformly distributed over the whole concrete section. It is supposed that a local bond failure occurs at each crack, and there is a relative slip between steel and surrounding concrete. The compatibility of deformation between the concrete and reinforcement is thus not maintained. The bond transfer length is a length of reinforcement adjacent to the crack where the compatibility of strain between the steel and concrete is not maintained because of partially bond breakdown and slip. It is an empirical measure of the bond characteristics of the reinforcement, incorporating bar diameter and surface characteristics such as texture. Based on results from a series of previously conducted long-term tests on eight restrained reinforced concrete slab specimens and material properties including creep and shrinkage of two concrete batches, the ratio of final bond transfer length after all shrinkage cracking, to THE initial bond transfer length is presented.

• Structural Monitoring and Maintenance
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• v.6 no.4
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• pp.269-289
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• 2019

This study investigated experimentally the response of thick reinforced concrete specimens having hollow cores with critical parameters. The investigation includes testing of twelve specimens that are solid and hollow-core slab models. Each specimen consists of two pieces, the piece dimensions are (1.2 m) length, (0.3 m) width and (20 cm) thickness tested under both monotonic and repeated loading. The test program is carried out to study the effects of load type, core diameters, core shape, number of cores, and steel fiber existence. Load versus deflection at mid span, failure modes, and crack patterns were obtained during the test. The test results showed that core shape and core number has remarkable influenced on cracking pattern, ultimate load, and failure mode. Also, when considering repeated loading protocol, the ultimate load capacity, load at yielding, and ductility is reduced.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.1-6
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• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the construction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have beem deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechanism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical program is developed using these joint models.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.448-455
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• 2005

In this paper, an analytical model for estimation of the time at which the concrete surface begins to dry is introduced to predict whether or not plastic shrinkage cracks occur. First of all, the validity of a consolidation model for bleeding of cement paste proposed by Tan et al. is verified by comparing the analytical results with the experimental results, and used to evaluate the rate and amount of bleed water of concrete. Also an analytical model for evaporation of bleed water which considers the effect of the temperature variation of concrete surface due to hydration heat on the evaporation rate is proposed, and the experimental and analytical results are then compared to verify the validity of the introduced model. In advance, the time at which the concrete surface begins to dry is estimated using above two analytical models, and compared with the experimental results about the time at which plastic shrinkage cracks occur. From the comparison, it is verified that the proposed model can predict the occurrence of plastic shrinkage cracking with comparative precision.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.108-115
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• 1990

This paper contains experimental studies on the flexural cracking behabior of PPC one-way slabs. Three post tensioned bonded PPC slabs with the same prestressing ratio and ultimate moment strength were tested. Based upon test results, this paper also presents the crack width prediction formula PPC slab. According to the crack theory developed mainly in Europe, crack width formula is given as the product of crack spacing and mean steel strain after decompression. Aaaaverage crack spacing formula is composed of many factors mainly such as concrete cover, concrete effective area in tension, sum of reinforcing bars perimeters and mixed reinforcements. In particular, it is very important to specify the bond characteristics of mixed reinforcements, since bond characteristics of PC bars are different from those of non-tensioned deformed bars. For this reason, a reduced bond coefficients for PS bars is employed in this study.

• KCI Concrete Journal
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• v.14 no.1
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• pp.8-14
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• 2002

This is the first of two part series on experimental studies of grout type transverse joints. In this study, grout type transverse joints between precast concrete slabs are statically tested to determine the cracking loads and ultimate shear capacities of the grout type transverse joints. The tests are performed with a loading equipment designed and constructed especially in the lab to induce shear failures on the joints of the test specimens. Shape of the transverse joints, grouting materials and amount of prestress are selected as test parameters for the study. The results indicate that epoxy is an excellent grouting material which can be used in limited locations where large tensile stress is acting on the slab. Longitudinal prestressing is also an effective method to increase the shear strength of the transverse joints. A rational method to estimate the cracking and ultimate loads for the design of grout type transverse joints is proposed based on the static loading tests. Success of the tests with shear loading equipment allowed continuing the research further onto the fatigue strength of the grout type joints, which will be presented in the second part of the paper.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.750-753
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• 2004

In this paper, experimental test on the full scale model of steel and concrete composite plate girder with prefabricated slabs under hogging moments was conducted cautiously and observed in order to study cracking in precast decks. Details of prefabricated slab transverse joints were determined from previous research. A test specimen was overhanging simple support beam, totally 28 meter length. Through the 4-point flexural test, the behaviour of the composite girder under hogging moments was observed. From the test results, crack development and crack widths were observed.

• Computers and Concrete
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• v.21 no.3
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• pp.321-333
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• 2018

Flat-slabs, being a significant structural component, not only reduce the dead load of the structure but also reduce the amount of concrete required for construction. Moreover the use of recycled aggregates lowers the impact of large scale construction to nearby ecosystems. Recycled aggregate based concrete being a quasi-brittle material shows enormous cracking during failure. Crack growth in flat-slabs is mostly in sliding mode (Mode II). Therefore sufficient sections need to be provided for resistance against such failure modes. The main objective of the paper is to numerically determine the ultimate load carrying capacity of two self-similar flat-slab specimens and validate the results experimentally for the natural aggregate as well as recycled aggregate based concrete. Punching shear experiments are carried out on circular flat-slab specimen on a rigid circular knife-edge support built out of both normal (NAC) and recycled aggregate concrete (RAC, with full replacement). Uniaxial compression and bending tests have been conducted on cubes, cylinders and prisms using both types of concrete (NAC and RAC) for its material characterization and use in the numerical scheme. The numerical simulations have been conducted in ABAQUS (a known finite element software package). Eight noded solid elements have been used to model the flat slab and material properties have been considered from experimental tests. The inbuilt Concrete Damaged Plasticity model of ABAQUS has been used to monitor crack propagation in the specimen during numerical simulations.

• Structural Engineering and Mechanics
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• v.50 no.4
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• pp.501-524
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• 2014

This paper presents a type of composite box girder with corrugated webs and concrete filled steel tube slab to overcome cracking on the web and reduce self-weight. Utilizing corrugated steel web improves the efficiency of prestressing introduced into the top and bottom slabs due to the accordion effect. In order to understand the loading capacity of such new composite structure, experimental and numerical analyses were conducted. A full-scale model was loaded monotonically to investigate the deflection, strain distribution, loading capacity and stiffness during the whole process. The experimental results show that test specimen has enough loading capacity and ductility. Based on experimental works, a finite element (FE) model was established. The load-displacement curves and stress distribution predicted by FE model agree well with that obtained from experiments, which demonstrates the accuracy of proposed FE model. Moreover, simplified theoretical analysis was conducted depending on the assumptions which were confirmed by the experimental and numerical results. The simplified analysis results are identical with the tested and numerical results, which indicate that simplified analytical model can be used to predict the loading capacity of such composite girder accurately. All the findings of present study may provide reference for the application of such structure in bridge construction.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.162-172
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• 1994

The flexural and horizontal shear behavior of overlaid concrete slabs with polymer interface is investigated in the present study. An experimental program was set up and several series of overlaid concrete slabs have been tested to study the effect of different surface preparations and dowel bars between old slab and overlay under service and ultimate loads. 'The cracking and ulti mate load behavior for various cases including acryl emulsion treatment and doweled joints has been studied. The present study indica.tes that the overlaid concrete slabs behave integrally with existing bottom slabs up to ultimate range for rough and doweled joints with polymer interface. The pres ent study provides a firm base for the realistic design of two-layered RC slabs in bridges.