• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10a
• /
• pp.559-564
• /
• 1998

The object of this thesis is an analytical study on shear deformation of reinforced concrete members using monte carlo method. Using the established experimental data that has been presented in various documents the stress-strain relationships curves of reinforced concrete (300kgf/$\textrm{cm}^2$~400kgf/$\textrm{cm}^2$) models are proposed. Finally, the theoretical values calculated using the analytical method developed in this study have been investigated in comparison with the experimental ones which were carried out earlier in order to prove its validity. From the results it has been shown that theoretical values agree quite well with experimental ones, and it could be pointed out that the presented analytical method is widely acceptable for the practical analysis of shear displacement of reinforced concrete members.

• Computers and Concrete
• /
• v.5 no.4
• /
• pp.401-416
• /
• 2008

The paper presents a methodology to model three-dimensional reinforced concrete members by means of embedded discontinuity elements based on the Continuum Strong Discontinuous Approach (CSDA). Mixture theory concepts are used to model reinforced concrete as a 3D composite material constituted of concrete with long fibers (rebars) bundles oriented in different directions embedded in it. The effects of the rebars are modeled by phenomenological constitutive models devised to reproduce the axial non-linear behavior, as well as the bond-slip and dowel action. The paper presents the constitutive models assumed for the components and the compatibility conditions chosen to constitute the composite. Numerical analyses of existing experimental reinforced concrete members are presented, illustrating the applicability of the proposed methodology.

• Structural Engineering and Mechanics
• /
• v.9 no.6
• /
• pp.601-613
• /
• 2000

Existing models for the shear strength degradation of reinforced concrete members present varied conceptual approaches to interpreting test data. The relative superiority of one approach over the others is difficult to determine, particularly given the sparseness of ideal test data. Nevertheless, existing models are compared using a suite of test data that were used for the development of one such model, and significant differences emerge. Rather than relying purely on column test data, the body of knowledge concerning degradation of concrete as a material is considered. Confined concrete relations are examined to infer details of the degradation process, and to establish a framework for developing phenomenologically-based models for shear strength degradation in reinforced concrete members. The possibility of linking column shear strength degradation with material degradation phenomena is explored with a simple model. The model is applied to the results of 7 column tests, and it is found that such a link is sustainable. It is expected that models founded on material degradation phenomena will be more reliable and more broadly applicable than the current generation of empirical shear strength degradation models.

• International Journal of Concrete Structures and Materials
• /
• v.6 no.2
• /
• pp.79-85
• /
• 2012

This paper presents the differences in growth of time-dependent strain values in reinforced cement concrete (RCC) and pre-stressed concrete (PSC) flexural members through experiment. It was observed that at any particular age, the time-dependent strain values were less in RCC beams than in PSC beams of identical size and grade of concrete. Variables considered in the study were percentage area of reinforcement, span of members for RCC beams and eccentricity of applied pre-stress force for PSC beams. In RCC beams the time-dependent strain values increases with reduction in percentage area of reinforcement and in PSC beams eccentricity directly influences the growth of time-dependent strain. With increase in age, a non-uniform strain develops across the depth of beams which influence the growth of concave curvature in RCC beams and convex curvature in PSC beams. The experimentally obtained strain values were compared with predicted strain values of similar size and grade of plane concrete (PC) beam using ACI 318 Model Code and found more than RCC beams but less than PSC beams.

• Structural Engineering and Mechanics
• /
• v.38 no.4
• /
• pp.459-477
• /
• 2011

Due to the low elastic modulus of FRP, concrete members reinforced with FRP rebars show greater deflections than members reinforced with steel rebars. Deflection is one of the important factors to consider the serviceability of horizontal members. In this study flexural test of AFRP reinforced concrete beams was performed considering reinforcement ratio and compressive strength as parameters. The test results indicated that flexural capacity and stiffness increase in proportion to the reinforcement ratio. The test results were compared with existing proposed equations for the effective moment of inertia including ACI 440. The most of the proposed equations were found to over-estimate the effective moment of inertia while the equation proposed by Bischoff and Scanlon (2007) most accurately predicted the values obtained through actual testing.

• Journal of the Korea Concrete Institute
• /
• v.11 no.4
• /
• pp.83-93
• /
• 1999

This paper presents tension stiffening effect of Reinforced concrete members obtained from experimental results on direct tension and bending. From the direct tension test program, crack patterns were investigated with tension softening behaviors of concrete. Tension stiffening effects and losses of strain energy were, also, analyzed from the load-deflection curve with the main experimental variables such as concrete strength, yielding stress and reinforcement ratio of rebar. Tension stiffening effect of RC members increase linearly until the first crack initiate, decrease inversely with number of cracks, and then decrease rapidly when splitting cracks are happened. The tension stiffening effect is shown to be more important at the member of lower reinforcement than that of higher. Therefore, it necessitates to consider the tension stiffening effects at a nonlinear analysis. From the above analysis, a tension stiffening model of concrete is proposed and verified by applying it to bending members. From the numerical analysis by finite element approach, it is shown that the proposed model evaluates a little higher in analyzing at nonlinear region of high strength concrete, but, perform satisfactorily in general.

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

• Computers and Concrete
• /
• v.22 no.1
• /
• pp.11-25
• /
• 2018

A numerical approach for the evaluation of the flexural response of Steel Fibrous Concrete (SFC) cross-sections with arbitrary geometry, with or without conventional steel longitudinal reinforcing bars is proposed. Resisting bending moment versus curvature curves are calculated using verified non-linear constitutive stress-strain relationships for the SFC under compression and tension which include post-peak and post-cracking softening parts. A new compressive stress-strain model for SFC is employed that has been derived from test data of 125 stress-strain curves and 257 strength values providing the overall compressive behaviour of various SFC mixtures. The proposed sectional analysis is verified using existing experimental data of 42 SFC beams, and it predicts the flexural capacity and the curvature ductility of SFC members reasonably well. The developed approach also provides rational and more accurate compressive and tensile stress-strain curves along with bending moment versus curvature curves with regards to the predictions of relevant existing models.

• Structural Engineering and Mechanics
• /
• v.13 no.3
• /
• pp.241-260
• /
• 2002

The effect of shear coupled with axial force variation on the inelastic seismic behaviour of reinforced concrete bridge piers is investigated in this paper. For this purpose, a hysteretic axial-shear interaction model was developed and implemented in a nonlinear finite element analysis program. Thus, flexure-shear-axial interaction is simulated under variable amplitude reversed actions. Comparative studies for shear-dominated reinforced concrete columns indicated that a conventional FE model based on flexure-axial interaction only gave wholly inadequate results and was therefore incapable of predicting the behaviour of such members. Analysis of a reinforced concrete bridge damaged during the Northridge (California 1994) earthquake demonstrated the importance of shear modelling. The contribution of shear deformation to total displacement was considerable, leading to increased ductility demand. Moreover, the effect of shear with axial force variation can significantly affect strength, stiffness and energy dissipation capacity of reinforced concrete members. It is concluded that flexure-shear-axial interaction should be taken into account in assessing the behaviour of reinforced concrete bridge columns, especially in the presence of high vertical ground motion.

• Journal of the Korea Concrete Institute
• /
• v.12 no.5
• /
• pp.81-92
• /
• 2000

A fixed angle softened truss model has been developed in order to predict both shear strength and deformation of reinforced concrete members. The model takes into account the contribution of concrete by accuming the angle of cracks in the postcracking concrete that coincides with the reinforced concrete principal compressive angle determined by the applied stresses. Therefore, this model is capable of predicting the contribution of concrete from the govering equilibrium and compatibility equations including the shear stress and strain developed along concrete diagonal crack. However, the model has a limiting range to be applicable for reinforced concrete members. This research proposes a new algorthm of fixed angle softened truss model capable of removing the limitation of applicability. The proposed algorithm adopts a new conception of constitutive laws. The average normal stresses of concrete in the x- y- directions can be calculated by transforming the principal stresses of concrete. The proposed algorthm is verified by comparing to the test results.