• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.13-20
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• 2009

The influence of steel fiber volume on the tension softening behavior in steel fiber-reinforced ultra high strength concrete was investigated. Three-point bending test (TPBT) with notched beams was performed and inverse analysis method by Uchida et al. was adopted to obtain the tension softening behaviors from the results of TPBT. It could be found that the intial stiffness was constant regardless of steel fiber volume, the increase of steel fiber volume fraction made the tensile strength higher, but all of the curves converged on an asymptote with a crack width. It was proposed the equation of softening curve expressed by combination of plastic behavior part and exponential descending behavior part considering the steel fiber volume fraction and $\omega_0$, which is corresponding to the maximum crack width of plastic area. Thereafter, the crack propagation analysis using finite element method with smeared crack model was also carried out and it was confirmed that the proposed equation had a good agreement with the experimental results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.237-248
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• 2011

Tensile softening characteristics play an important role in the structural behavior of steel fiber-reinforced ultra high performance concrete. Tension softening modeling and numerical analysis method are necessary for the prediction of structural performance of steel fiber-reinforced concrete. The numerical method to predict the flexural behavior is proposed in this study. Tension softening modeling is carried out by using crack equation based on fictitious crack and inverse analysis in which load-crack opening displacement relationship is considered. Thereafter material modeling is performed considering tension softening. The comparison of moment-curvature curves of the numerical analysis results with the test results indicates a reasonable agreement. Therefore, the present numerical results prove that good prediction of flexural behavior of steel fiber-reinforced ultra high performance concrete beams can be achieved by employing the proposed method.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.421-424
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• 2008

Ultra high strength steel fiber-reinforced concrete is characterized with high tensile strength and ductility. This paper revealed the influence of fiber volume fraction on the tensile softening behaviour of ultra high strength steel fiber-reinforced concrete and developed tensile softening model to predict the deformation capacity by finite element method analysis with experimental results. The initial stiffness of ultra high strength steel fiber-reinforced concrete was constant irrespective of fiber volume fraction. The increase of fiber volume fraction improved the flexural tensile strength and caused more brittle softening behaviour. Finite element method analysis proposed by Uchida et al. was introduced to obtain the tensile softening curve from three point notched beam test results and we proposed the tensile softening model as a function of fiber volume fraction and critical crack width.

• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.205-212
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• 1996

This paper presents progressive fracture analysis of concrete using boundary element method and its stabilizing technique. To determine ultimate strength and to predict nonlinear behavior of concrete during progressive crack growth, the modelling of fracture process zone is done based on Dugdale-Barenblatt model with linear tension-softening curve. We regulate displacement and traction boundary integral equation of solids including crack boundary and analyze progressive fracture of concrete beam and compact tension specimen. Also a numerical technique which considers the growth of stress-free crack of concrete during the analysis and removes snapback of postpeak behavior is proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.101-110
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• 2014

Expansion agent is a very effective admixture for prevention of cracking due to autogenous/drying shrinkage and this can induce internal chemical prestress to embedded reinforcement. In this paper, tension-softening and hardening in cement mortar with steel and CSA expansion agent are experimentally evaluated. Cement mortar with steel reinforcement is prepared and tensile strength test is performed for evaluation of cracking and tensile behavior. In spite of slightly reduced strength and elasticity in CSA mortar, significantly increased tension-hardening behavior is evaluated in CSA mortar with induced chemical prestress. Furthermore previous tension softening models are compared with the test results and improvement are proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.433-436
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• 2008

In order to estimate the mechanical properties of ultra high performance concrete, the most important is to evaluate its tensile behavior. The tensile behavior of concrete is generally characterized by the elastic behaviour before cracking and tensile stress-crack width relationship after cracking. We carried out the direct tensile and flexural tensile test and compared the tensile behaviors obtained by the direct tensile test and by inverse analysis of the flexural tensile test results. We compared the obtained tensile behavior with that of JSCE recommendations for ultra high performance concrete as well. we could see that the tensile stress-crack width relationship obtained from the flexural tensile test results using inverse analysis had good agreement with directly obtained tensile behaviour with direct tensile test and showed similar tensile softening behaviour introduced in JSCE recommendations for ultra high performance concrete.

• Elastomers and Composites
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• v.39 no.1
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• pp.61-70
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• 2004

This work is about the development or asphalt sealant using the waste edible oil. Asphalt sealant has been used for crack filler and bridge deck joint sealer Several plasticizers such as aromatic or paraffin process oils, DOP, Bunker C fuel oil, and waste edible oil were compounded with the basic components such as asphalt(AP-5), a thermoplastic elastomer(SBS triblock copolymer), a tackifying agent(petroleum resin), and stabilizers. Penetration, softening point, ductility, and elongation by tensile adhesion of those asphalt sealant compounds were measured. Their properties were changed largely depending on both the type and content of plasticizers. Waste edible oil and DOP were the best plasticizers for the low temperature tensile adhesion characteristics. Penetration and elongation by tensile adhesion of asphalt sealant compounds increased with the increase of waste edible oil content and decreased with the increase of talc content. The manufacture of asphalt sealant with low penetration and excellent low temperature tensile adhesion was possible by the recipe optimization.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.64-71
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• 2016

In this paper, when the composite beam is made with UHPC deck and steel girder, the steel girder takes the form of the inverted-T shape without top flange because of high strength and stiffness of UHPC deck. There is no evaluation by experiment and analysis about the shear connector behavior on the web of steel girder and flexural behavior of inverted-T shape composite beam. By this reason, this study compares between experiment and analysis by using tension softening model of UHPC on the basis of flexural test results of 16 members considering compressive strength of UHPC, spacing of stud and thickness of deck as variables. The results of tensile strength of UHPC by inverse analysis were 6.57 MPa(in case of 120 MPa) and 9.57 MPa(in case of 150 MPa). In case of the test members with small stud spacing, the results of analysis and test were close clearly, and the test members with thick deck and low UHPC compressive strength also similar, but effects were small. As it compared between analysis and experiment totally, the results of analysis and experiment agree well. So the tension softening model of UHPC is reasonably reflected on the real behavior of composite beam of UHPC.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.340.1-340
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• 2002

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.283-290
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• 2015

This paper proposes a method for predicting flexural strength of hybrid steel fiber-reinforced ultra-high strength concrete beams. It includes an experimental test framework and associated numerical analyses. The experimental program includes flexural test results of hybrid steel fiber-reinforced ultra-high strength concrete beams with steel fiber content of 1.5% by volume. Tensile softening characteristics play an important role in the structural behavior of steel fiber-reinforced ultra high performance concrete. Tension softening modeling is carried out by using crack equation based on fictitious crack and inverse analysis in which load-crack mouth opening displacement relationship is considered. The comparison of moment-curvature curves of the numerical analysis results with the test results shows a reasonable agreement. Therefore, the numerical results confirms that good prediction of flexural behavior of steel fiber-reinforced ultra high strength concrete beams can be achieved by employing the proposed method.