• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.763-768
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• 2000

In this study, the tests were performed on a series of reinforced concrete strip specimens to investigate a cracking behavior of reinforced concrete voided slab bridge. Also, the mid-span deflections, the crack widths and failure mode of reinforced concrete strip specimens were studied. It was found that serviceability of cracking and deflection at reinforced concrete voided slab bridge which were constructed and designed under verifying serviceability as design criteria are lower than common reinforced concrete member. On the basis of the experimental results, it is more reasonable concrete to evaluate crack occurring $f_r=2.0\surd{f_{ck}}$ rather than modulus of rupture of concrete, $f_r=0.8\surd{f_{ck}}$

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.469-474
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• 1998

To overcome the common deficiencies found in two-way slabs, such as excessive cracking around columns, excessive deflections and low punching shear strength, it was proposed to investigate the strategic use of steel fiber-reinforced concrete. Providing fiber-reinforced concrete results in an increase in the punching shear resistance, a significant increase in the ductility, greater post-cracking stiffness and better crack control.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.3-9
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• 2007

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

• Structural Engineering and Mechanics
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• v.68 no.3
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• pp.345-358
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• 2018

Heterogeneous structure and, particularly, low resistance to tension stresses leads to different mechanical properties of the concrete in different loading situations. To solve this problem, the tension zone of concrete elements is reinforced. Development of the cracks, however, becomes even more complicated in the presence of bar reinforcement. Direct tension test is the common layout for analyzing mechanical properties of reinforced concrete. This study investigates scatter of the test results related with arrangement of bar reinforcement. It employs results of six elements with square $60{\times}60mm$ cross-section reinforced with one or four 5 mm bars. Differently to the common research practice (limited to the average deformation response), this study presents recordings of numerous strain gauges, which allows to monitor/assess evolution of the deformations during the test. A simple procedure for variation assessment of elasticity modulus of the concrete is proposed. The variation analysis reveals different deformation behavior of the concrete in the prisms with different distribution of the reinforcement bars. Application of finite element approach to carefully collected experimental data has revealed the effects, which were neglected during the test results interpretation stage.

• Steel and Composite Structures
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• v.9 no.6
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• pp.569-584
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• 2009

Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.404-409
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• 2005

The reinforced concrete blocks for reinforced earth layer are combined with soil structures consisted of facing unit, reinforcing materials and soil. Those environmentally friendly facing units of reinforced concrete blocks are made of mine waste and tailing and that will be played a role of the effects of recycling use of wasted resources. The block are consisted of three types as curved or straight in order to control topography. The systems are also not limited to wall hight so that they are effectively used for protecting the slope of banking and cutting of earth works. The reinforced concrete blocks developed this time will be effectively applied for not only retaining wall, road, park, golf course, public office building constructions but also protecting of slope stabilization projects.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.35-46
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• 1999

The steel fiber reinforced concrete may affect substantially to the tension stiffening at post cracking behavior. Even if several tension stiffening models exist, they are for plain and normal strength concrete. Thus, the development of tension stiffening models for steel fibrous high strength RC members are necessary at this time when steel fiber reinforced and high strength concretes are common in use. This paper presents tension stiffening effects from experimental results on direct tension members with the main variables such as concrete strength, concrete cover depth, steel fiber quantity and aspect ratio. The comparison of existing models against experimental results indicated that linear reduced model closely estimated the test results at normal strength level but overestimated at high strength level. Discontinuity stress reduced model underestimated at both strength levels. These existing models were not valid enough in applying at steel fibrous high strength concrete because they couldn't consider the concrete strength nor section area. Thus, new tension stiffening models for high strength and steel fiber reinforced concrete were proposed from the analysis of experimental results, considering concrete strength, rebar diameter, concrete cover depth, and steel fiber reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.63-68
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• 2001

It is now common practice to strengthen reinforced concrete beams by steel plates to their tention surfaces. Such plated beams are designed for flexure using conventional prediction equation and assumption that full bond will be developed between the concrete and the plates. Very advanced design rules have already been developed at the University of Adelaide for adhesive bonding steel plates to reinforced concrete beams in order to prevent premature debonding. This work on plated continuous reinforced concrete beams is to determine experimentally whether these design rules, that were developed for steel plated simply supported beams, could be applied to steel and FRP plated continuous beams. This paper also suggests how to increase the ductility of plated beams.

• Computers and Concrete
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• v.5 no.3
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• pp.195-216
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• 2008

This paper presents a new hypoelasticity model which was implemented in a nonlinear finite element formulation to analyze reinforced concrete (RC) structures. The model includes a new hypoelasticity constitutive relationship utilizing the rotation of material axis through successive iterations. The model can account for high nonlinearity of the stress-strain behavior of the concrete in the pre-peak regime, the softening behavior of the concrete in the post-peak regime and the irrecoverable volume dilatation at high levels of compressive load. This research introduces the modified version of the common application orthotropic stress-strain relation developed by Darwin and Pecknold. It is endeavored not to violate the principal of "simplicity" by improvement of the "capability" The results of analyses of experimental reinforced concrete walls are presented to confirm the abilities of the proposed relationships.

• Structural Engineering and Mechanics
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• v.23 no.5
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• pp.469-486
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• 2006

The main objective of this study was to investigate the seismic behavior of damaged reinforced concrete frames rehabilitated by introducing cast in place reinforced concrete infills. Four bare and five infilled frames were constructed and tested. Each specimen consisted of two (twin) 1/3-scale, one-bay and two-story reinforced concrete frames. Test specimens were tested under reversed-cyclic lateral loading until considerable damage occurred. RC infills were then introduced to the damaged specimens. One bare specimen was infilled without being subjected to any damage. All infilled frames were then tested under reversed-cyclic lateral loading until failure. While some of the test frames were detailed properly according to the current Turkish seismic code, others were built with the common deficiencies observed in existing residential buildings. The variables investigated were the effects of the damage level and deficiencies in the bare frame on the seismic behavior of the infilled frame. The deficiencies in the frame were; low concrete strength, inadequate confinement at member ends, 90 degree hooks in column and beam ties and inadequate length of lapped splices in column longitudinal bars made above the floor levels. Test results revealed that both the lateral strength and lateral stiffness increased significantly with the introduction of reinforced concrete infills even when the frame had the deficiencies mentioned above. The deficiency which affected the behavior of infilled frames most adversely was the presence of lap splices in column longitudinal reinforcement.