• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.133-140
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• 1998

Material nonlinear analyses of RC(Reinforced Concrete) beams considering the tension stiffening effect and plastic hinge length have been conducted. Instead of taking the sophisticated layer approach which has some limitations in application to the large structures with many degrees of freedom. the moment-curvature relationships of RC sections previously constructed through the section analysis have been used. To reduce the numerical instability in nonlinear analysis and to remove the imprecision in calculation of ultimate resisting capacity, according to the used finite element mesh size, the tension stiffening effect and plastic hinge length have been taken into consideration. Finally, correlation studies between analytical and experimental results have been conducted with the objective to establish the validity of the proposed algorithms.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.285-288
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• 2008

A model for the effective moment of inertia $I_{\epsilon}$ as expressed in Branson's equation, in which reduction of the flexural rigidity of RC beams due to cracking are aptly taken into accoun,t is presented. However, KCI Code isn`t considered tension stiffening as it is in debonding of reinforcing bar. Therefore, this equation need to set up suitable to our design Code. The experimental work consisted of casting and testing a total of 6 simply supported reinforced concrete beams and a total of 4 continuos reinforced concrete beams under two point concentrated loads. Main parameters are concrete strength, coverage, bond between concrete and reinforcing bars, are known as have an effect on deflection and tension stiffening. Every test beams had the same $250{\times}350$mm rectangular section, with a simply supported clear span of 4,400 mm and a continuos clear span of 6,500 mm. Comparison of the test results with values obtained using the KCI Code equation of the effective moment of inertia showed a noticeable difference.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.419.1-419
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• 2002

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.121-131
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• 2022

The main goal of this study is to prepare a program for analyzing High Strength Steel Fibrous Reinforced Concrete (HSSFRC) slabs and predict the response and strength of the slab instead of preparing a prototype and testing it in the laboratory. For this purpose, new equations are proposed to represent the material properties of High Strength Steel Fibrous Reinforced Concrete. The proposed equations obtained from performing regression analysis on many experimental results using statistical programs. The finite element method is adopted for non-linear analysis of the slabs. The eight-node "Serendipity element" (3 DoF) is chosen to represent the concrete. The layered approach is adopted for concrete elements and the steel reinforcement is represented by a smeared layer. The compression properties of the concrete are modeled by a work hardening plasticity approach and the yield condition is determined depending on the first two stress invariants. A tensile strength criterion is adopted in order to estimate the cracks propagation. many experimental results for testing slabs are compared with the numerical results of the present study and a good agreement is achieved regarding load-deflection curves and crack pattern. The response of the load deflection curve is slightly stiff at the beginning because the creep effect is not considered in this study and for assuming perfect bond between the steel reinforcement and the concrete, however, a great agreement is achieved between the ultimate load from the present study and experimental results. For the models of the tension stiffening and cracked shear modulus, the value of Bg and Bt (Where Bg and Bt are the curvature factor for the cracked shear modulus and tension stiffening models respectively) equal to 0.005 give good results compared with experimental result.

• Structural Engineering and Mechanics
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• v.9 no.5
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• pp.491-504
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• 2000

A convenient method for enhancing the strength and stiffness of existing reinforced concrete beams is to bond adhesively steel plates to their tension faces. However, there is a limit to the applicability of tension face plating as the tension face plates are prone to premature debonding and, furthermore, the addition of the plate reduces the ductility of the beam. An alternative approach to tension face plating is to bond adhesively steel plates to the sides of reinforced concrete beams, as side plates are less prone to debonding and can allow the beam to remain ductile. Debonding at the ends of the side plates due to flexural forces, that is flexural peeling, is studied in this paper. A fundamental mathematical model for flexural peeling is developed, which is calibrated experimentally to produce design rules for preventing premature debonding of the plate-ends due to flexural forces. In the companion paper, the effect of shear forces on flexural peeling is quantified to produce design rules that are applied to the strengthening and stiffening of continuous reinforced concrete beams.

• Computers and Concrete
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• v.1 no.1
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• pp.77-98
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• 2004

This paper presents a numerical model for simulating the nonlinear response of reinforced concrete (RC) shear walls subject to cyclic loadings. The material behavior of cracked concrete is described by an orthotropic constitutive relation with tension-stiffening and compression softening effects defining equivalent uniaxial stress-strain relation in the axes of orthotropy. Especially in making analytical predictions for inelastic behaviors of RC walls under reversed cyclic loading, some influencing factors inducing the material nonlinearities have been considered. A simple hysteretic stress-strain relation of concrete, which crosses the tension-compression region, is defined. Modification of the hysteretic stress-strain relation of steel is also introduced to reflect a pinching effect depending on the shear span ratio and to represent an average stress distribution in a cracked RC element, respectively. To assess the applicability of the constitutive model for RC element, analytical results are compared with idealized shear panel and shear wall test results under monotonic and cyclic shear loadings.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.23-33
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• 2008

The moment redistribution in continuous reinforced concrete beams is very feasible phenomenon, by which the efficiency and the economy in designing reinforced concrete members can be enhanced. However, to understand the structural behavior by moment redistribution phenomenon, it is desirable to verify its mechanism experimentally considering tension stiffening effect, the relationship of moment redistribution and beam deflection, crack pattern, and effective stiffness. Six reinforced concrete continuous beam specimens were fabricated, and each specimen had a dimension of 250 mm $\times$ 350 mm and 7,000 mm long. The location of de-bonding was taken as the primary test parameter to investigate tension stiffening effect. The moment redistribution ratio of the specimens was different depending on the position of de-bonding, and in particular no moment redistribution was observed when de-bonding exist at both ends, the maximum negative moment region and the maximum positive moment region.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.459-467
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• 2008

This paper describes a proposal for average crack width and immediate deflection calculation in structural concrete members. The model is mathematically derived from actual bond stressslip relationships and tension stiffening effect between reinforcement and the surrounding concrete, and the actual strains of steel and concrete are integrated respectively along the embedded length between the adjacent cracks so as to obtain the difference in the axial elongation. With these, a model for average crack width and immediate deflection in reinforced concrete flexural members are proposed utilizing difference in the axial elongation and average steel strain and moment-curvature relationship with taking account of bond characteristics. The model is applied to the test specimens available in literatures, and the crack width and deflections predicted by the proposal equation in this study are closed to the experimentally measured data compared the current code provisions.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.141-144
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• 2008

Deflection in terms of serviceability of reinforced concrete structures is considered as one of significant factor. Domestic concrete specification offers a procedure to evaluate deflection using effective moment of inertia at cracked section, which has been known as Branson's equation in ACI. Branson's equation was derived from statistical analysis of maximum deflection of flexural members, but is somewhat weak in no reflection of bond characteristics between reinforced bars and concrete, such as tension stiffening effect. Therefore, present code creates difference from actual deflection. In this study, experiments about deflection of RC beams was completed to compare domestic standard and Eurocode 2, which calculates deflection considering tension stiffening effect. Four RC beams were built and tested, and initial modulus of elasticity and tensile strength of concrete used in the test was calculated by each design standard.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.195-206
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• 2005

Experimental research was performed on the 6m-6m two-span, continuous composite beams. Background research for the crack width control of continuous composite bridges in the Eurocode-4 is reviewed and equationsfor the calculation of crack width considering tension stiffening are presented. The behavior of the continuous composite beams was investigated using the initial and stabilized cracking process of the concrete slab in tension. Test results showed that the current requirement of minimum reinforcement for ductility in Korea Highway Bridge Design Codes could be reduced. The flexural stiffness of cracked continuous composite beams can be evaluated by the uncracked section analysis until the stabilized cracking stage. An empirical equation for the relationship between the stress of tensile reinforcements and crack width was obtained from the test results.