• Computers and Concrete
• /
• v.1 no.4
• /
• pp.417-432
• /
• 2004

An analytical model which can simulate the post-cracking nonlinear behavior of reinforced concrete (RC) members such as bars and panels subject to uniaxial and biaxial stresses is presented. The proposed model includes the description of biaxial failure criteria and the average stress-strain relation of reinforcing steel. Based on strain distribution functions of steel and concrete after cracking, a criterion to consider the tension-stiffening effect is proposed using the concept of average stresses and strains. The validity of the introduced model is established by comparing the analytical predictions for reinforced concrete uniaxial tension members with results from experimental studies. In advance, correlation studies between analytical results and experimental data are also extended to RC panels subject to biaxial tensile stresses to verify the efficiency of the proposed model and to identify the significance of various effects on the response of biaxially loaded reinforced concrete panels.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.873-878
• /
• 2000

Tension stiffening effects of reinforced concrete member with large diameter bar, mainly used at reactor building of nuclear power plant, are studied by uniaxial structural tests. Bond length and stress of steel bar, size of steel bar, and compressive strength of concrete are evaluated to tension stiffening by uniaxial tests. Problems and solution during the uniaxial test are suggested. The prevent splitting cracks, concrete cover-to-bar diameter ratio $c/d_{b}$ is kept 2.6~2.8. Because the bond length is increased as the size of steel bar, the specimen length of the D35 steel bar is required at least 2.0 m. The specimen length must be decided with bond length as well as concrete cover-to-bar diameter ratio to prevent splitting crack.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.17-20
• /
• 2005

Moment-curvature relation of RC pier is influenced greatly in occurrence form of crack and difference is happened according to consideration existence and nonexistence of tension stiffening effect. However, studies considering these is very insufficient misgovernment. Also, it is sometimes unavoidable lap splice of axial reinforcement in plastic hinge region of RC piers. However, specific design standard about lap splice of axial reinforcement is unprepared real condition and study about effect that lap splice of axial reinforcement get in occurrence form of crack is insufficient misgovernment. Therefore, in this paper, experiments are performed with hollow RC piers that do lap splice of axial reinforcement by main variable. And this study present analytical method about moment-curvature relation of hollow RC pier that consider tension stiffening effect and analyze effect that lap splice of axial reinforcement gets in occurrence form of crack. Analytic method of moment-curvature relation of RC pier that present in this study shows very similar motion with experiment result and crack interval of RC pier is suffering dominate impact in the augmented reinforcement amount by lap splice and average crack interval decreases as lap splice ratio increases.

• Journal of the Korea Concrete Institute
• /
• v.15 no.6
• /
• pp.915-923
• /
• 2003

This paper presents the test results of total 35 direct tensile specimens to investigate the effect of high-strength concrete on the tension stiffening effect in axially loaded reinforced concrete tensile members. Three kinds of concrete strength 25, 60, and 80 MPa were included as a major experimental parameter together with six concrete cover thickness ratios. The results showed that as higher strength concrete was employed, not only more extensive split cracking along the reinforcement was formed, but also the transverse crack space became smaller. Thereby, the effective tensile stiffness of the high-strength concrete specimens at the stabilized cracking stage was much smaller than those of normal-strength concrete specimens. This observation is contrary to the current design provisions, and the significance in reduction of tension stiffening effect by employment of high-strength concrete is much higher than that would be expected. Based on the present results, a modification factor is proposed for accounting the effect of the cover thickness and the concrete strength.

• Journal of Industrial Technology
• /
• v.18
• /
• pp.87-95
• /
• 1998

Cracking is considered to be one of the important factors in determining the durability of reinforced concrete structures. When the bending stress exceeds the modulus of rupture of the concrete, cracking form along the length of members. The total load is transferred across these cracks by the reinforcement, but the concrete between cracks is still capable of carrying stresses due to the bond between steel and concrete. This phenomenon is called the tension stiffening effect. The tension stiffening effect is affected by many variables, such as the bond stress, strength of concrete, interrocking of aggregate, type of steel, and dowel action of steel. Also, this tension stiffening effect is usually quite significant in beams under service loading, and must be taken into account in the calculation of deflection and crack widths. In this study, the experiment was carried out on types of specimen, strength of concrete, and steel ratio and finite element analysis were compared in terms of load-deflection relationship, crack pattern.

• Nuclear Engineering and Technology
• /
• v.36 no.6
• /
• pp.512-527
• /
• 2004

This paper describes the finite element (FE) analysis results of a 1/4 scale model of a prestressed concrete containment vessel (PCCV) by considering the tension stiffening effect, which is a result of the bond effect between the concrete and the steel. The tension stiffening model is assumed to be an exponential form based on the relationship between the average stress and the average strain of the concrete. The objective of the present FE analysis is to evaluate the ultimate internal pressure capacity of the PCCV, as well as its failure mechanism, when the PCCV model is subjected to a monotonous internal pressure beyond is design pressure capacity. With the commercial code ABAQUS, the FE analysis used two concrete failure criteria: a 2-dimensional axi-symmetric model with modified Drucker-Prager failure criteria and a 3-dimensional model with a damaged plasticity mod디. The results of our FE analysis on the ultimate pressure capacity and failure modes of PCCV have a good agreement with the experimental data.

• Journal of the Korea Concrete Institute
• /
• v.22 no.6
• /
• pp.761-768
• /
• 2010

When cracks occur in reinforced concrete structures, a steel carries all tensile force at crack section, while the concrete between cracks carries a part of the tensile force due to bond, so that the steel is less elongated. This is called the tension-stiffening effect, that plays an important role in verification of a serviceability limit state. But it is a complicated work to use a complex strain distribution between cracks, therefore an average strain is used to calculate deflection and crack width. In Eurocode 2, tension-stiffening effect expressed in the first order form or the second order form is used in calculating an average curvature for deflection. In this study for a flexural member deflection and crack width are calculated using various models for the tension-stiffening effect and the results are compared with the values of Eurocode 2 and KCI provisions. As results, the predicted values using the second order form are appeared to be well agreed with the experimental values and it could secure more analytical consistency.

• Journal of the Korea Concrete Institute
• /
• v.23 no.1
• /
• pp.87-98
• /
• 2011

Crack formations are inevitable in reinforced concrete structures. To estimate crack widths, empirical formulae are used widely and indirect crack controling methods of limiting bar spacing and bar diameter are also used due to their simplicity. In EC2, the characteristic crack width is calculated by multiplying maximum crack spacing and average strain. In this study, limit values of maximum bar spacing and bar diameter are examined as the material characteristics are varied. Two models of tension stiffening effect and maximum crack spacing and their effects are evaluated. The obtained results are compared with the values obtained using KCI method. The results showed that a significant difference is found when two tension stiffening effect are employed, and an under-estimation is found when 2nd order tension stiffening effect and maximum crack spacing limit from Part II were implemented. Therefore, a rational indirect crack control method attained using the tension stiffening effect of 2nd order form is needed. Also, a consistency in serviceabiliy analysis in flexural members needs to be secured. In order to achieve these goals, two crack controling models are suggested.

• Magazine of the Korea Concrete Institute
• /
• v.3 no.1
• /
• pp.79-85
• /
• 1991

This paper aims at experimentally investigating the relationship between tensile load and average strain in the tension zone of SFRC beam. Also, it is attempted to find post cracking tension behavior of SFRC under tensile loading condition. The tension stiffening test is conducted on the long prizm of SFRC which embeds reinforcing bar in both ends of member. From this study, an empirical equation which represents the tension stiffening effect(i.e.effect of increasing tensile-~3trengthening contnbuted by SFRC when the reinforcing bar embeded in the SFRC member is under tensile loading condition) as a function of the average strain is presented .

• Computers and Concrete
• /
• v.18 no.1
• /
• pp.139-154
• /
• 2016

Since the concrete strength around the reinforcement rebar affects the tension stiffening, the tension stiffening effect of ultra high performance concrete on the concrete members reinforced by steel rebar is examined by testing the specimens with circular cross section with the length 850 mm reinforced by a steel rebar at the center of a specimen's cross section in this research. Conducting a tensile test on the specimens, the cracking behavior is evaluated and a curve with an exponential descending branch is obtained to explain the post-cracking zone. In addition, this paper proposes an equation for this branch and parameters of equation is obtained based on the ratio of cover thickness to rebar diameter (c/d) and reinforcement percentage (${\rho}$).