Theoretical and numerical analysis of reinforced concrete beams with confinement reinforcement (original) (raw)
Related papers
Magazine of Concrete Research, 2004
Compared with normal concrete, high-strength concrete has higher strength but is generally more brittle. Its use in a reinforced concrete structure, if not properly controlled, could lead to an unsustainable reduction in ductility. However, confinement could be provided to improve the ductility of the structure. In this study, the effects of concrete strength and confinement on the flexural ductility of reinforced concrete beams have been evaluated by means of complete moment–curvature analysis of beam sections cast in different concretes and provided with different confinements. The results reveal that the use of high-strength concrete at a constant tension steel ratio would increase the flexural ductility, but at a constant tension to balanced steel ratio would decrease the flexural ductility. In contrast, the provision of confinement would always increase the flexural ductility. It does this in two ways: first, it increases the balanced steel ratio so that, at the same tension st...
Analysis of Confinement Effect on Strength and Ductility in Reinforced Concrete Structures
2014
The lateral confinement in reinforced concrete structural components is an essential parameter to allow designer to use a sufficient percentage of transverse reinforcement in order to ensure the required strength and ductility for the structure. This paper deals mainly with the influence of lateral confinement on strength and ductility in reinforced concrete structures designed according to Algerian standards. An overview of the non-linear static analysis method is described below to better understand this analysis. Two different representative structures designed according to Algerian code for the design of earthquake resistant buildings (RPA99/v2003) are identified for the purpose of this study. This analysis provides the capacity curves for each structure with regard to the compressive strength and the volume percentage of the transverse reinforcement. The results obtained show that the lateral confinement improves widely the strength and the local ductility of the structure elem...
Utilising confinement reinforcement for shear resistance in reinforced concrete structures
Magazine of Concrete Research, 2013
Common transverse reinforcement of reinforced concrete members with circular cross-section consists of round ties or spirals. Its purpose in members that are not subjected to significant shear loading is to provide proper confinement for concrete, and eliminate buckling of the longitudinal reinforcement bars. If spirals are to be used as both shear enabler and confiner for reinforced concrete beams then, under combined action of moment and shear, spirals will be required to provide or contribute to proper shear resistance. Hence, a proper assessment for spiral shear contribution is required. The validity of concepts which underline current methods for shear design used in design codes will be investigated in this paper, especially for beams with the shear configuration, which violates basic code rules on forming a truss. A simplified sectional model based on sectional crack analysis and a corresponding approach in assessing the shear contribution of spiral shear reinforcement are presented. A method for evaluating the shear capacity of beams with spirals has also been proposed.
Effect of confinement on curvature ductility of reinforced concrete beams
2014
It is a fact that the strength and ductility of the concrete is highly dependent on the confinement level provided by the lateral reinforcement. In the current design codes design of strength is separated with deformability. Evaluation of deformability is independent of some key parameters of concrete and steel. In the present study curvature ductility of a RCC beams with different level of confinements are calculated analytically following Hong K N and Han S H (2005) Model and Saaticioglu and Razvi (1992) Model and compared with experimental results. Six rectangular RCC beams having same cross section and main reinforcements are analysed by using OPENSEES software. Different level of lateral confinement in beams is induced by two legged and three legged stirrups provided with three different spacing. For experimental study six RCC beams are cast with stirrups provided at spacing of 100 mm, 150 mm and 250 mm. Three beams are cast with two legged and three beams are cast with three legged stirrups. Analytical observation is that the curvature ductility increases with decrease in spacing of stirrups and increase in number of legs of stirrups i.e. lateral confinement increases the curvature ductility of beam. The variation with respect to spacing is more compared to number of legs of stirrups. It is proven by using both models. The same trends are observed through experimental results. Analytical results following Saatcioglu and Razvi (1995) Model are found to be in well agreement with the experimental results. vi ACKNOWLEDGEMENT The satisfaction and euphoria on the successful completion of any task would be incomplete without the mention of the people who made it possible whose constant guidance and encouragement crowned out effort with success. I would like to express my heartfelt gratitude to my esteemed supervisors Prof. A. Patel and Prof. Robin Davis for their technical guidance, valuable suggestions, and encouragement throughout the experimental and analytical study and in preparing this thesis. It has been an honour to work under Prof. A. Patel and Prof. Robin Davis, whose expertise and discernment were Key in the completion of this project. I am grateful to the Dept. of Civil Engineering, NIT ROURKELA, for giving me the opportunity to execute this project, which is an integral part of the curriculum in M.Tech programme at the National Institute of Technology, Rourkela. Many thanks to my friends who are directly or indirectly helped me in my project work for their generous contribution towards enriching the quality of the work. I would also express my obligations to Mr.
Ductility of reinforced concrete sections with confined compression zones
Earthquake Engineering & Structural Dynamics, 1975
Confinement of concrete in circular spiral steel binders imparts to it considerable ductility and also some increase in strength. This property can be utilized in designing concrete structures to withstand seismic forces where the members are required to possess not only strength but also energy absorbing capacity. Assuming the stress-strain behaviour of confined concrete as elastic-plastic, the ductility factor for strain and the strength factor (denoting increase in strength) have been determined for concrete confined to different degrees. Similarly, assuming the moment-curvature behaviour of reinforced concrete sections with confined compression concrete to be elasticplastic, the ductility factor for curvature has been determined for such beams. The computed moment-curvature plots have been found to compare satisfactorily with tests on 18 beams. Ductility factors for curvature of singly and doubly reinforced concrete sections with compression concrete confined to different degrees have been determined and presented for certain typical cases. Such plots would be of use in designing reinforced concrete beam sections for required ductility.
2014
Ductility is a mechanical property used to describe the extent to which materials can be deformed plastically without fracture giving warning of impending failure. In this paper the effect of increasing the strength in the compression zone of reinforced concrete beams on ductility was investigated. Seven reinforced concrete beams were tested for this purpose. The tested beams were divided into two groups depending on the manner at which the strength of the compression zone was increased. In the first group, the increase was done by increasing the amount of compression reinforcement. Four ratios of compression reinforcement were adopted. In the second group, the increase in the strength of the compression zone was done by increasing the concrete compressive strength in the upper third of the cross section which was subjected to compression stresses. Four compressive strengths were adopted .One beam was used as reference for the two groups. It was found that, the compression zone stre...
The Effect of Confinement with steel on Seismic Behavior of Reinforced Concrete Frames
4th. International Congress on Civil Engineering , Architecture and Urban Development, 2016
The strength and ductility of concrete improve under multiaxial compressive stress. This can be done with concrete confinement technique, using steel jackets. Over the past years, several researchers have developed various stress-strain models for concretes confined with longitudinal and transverse reinforcement steel. This article presented the results from the application of a non-linear finite element method (NFEM) to a normal concrete frame, and concrete frames confined via confinement models developed by various researchers. The effect of the stress-strain models proposed by these researchers on linear and non-linear behaviors of the concrete frame, crack pattern of all models, and ductility parameter of the frames were discussed. Laboratory findings of a concrete frame were selected, and its aforementioned parameters were examined after the calibration of the numerical model and ensuring the validity and accuracy of the findings. Finally, the pushover curves of all models were plotted and compared. Then, the crack patterns of all models were interpreted and ductility parameters were computed. Results from the finite element method (FEM) showed that all pushover curves obtained from the finite element analysis had a linear behavior similar to the validated and laboratory models. Among the obtained pushover curves, models developed by Mander et al. (1988), and Saatcioglu and razvi (1992) had the highest conformity with both the calibrated and laboratory models. The reason behind this conformity was that these researchers considered all effective parameters in developing their stress-strain models.
Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017
Many researches have been conducted in the structural engineering field in order to develop efficient numerical tools able to reproduce the complex nonlinear behavior of reinforced concrete structures. In the case of slender elements, enhanced beam models have been developed to try to introduce shear effects, but in these models, the transverse steel is sometimes taken into consideration with approximated manner or often not at all. However, as shown by some experimental tests, the amount of transverse reinforcement triggers significantly the behavior of beam elements, especially under cyclic loading. The present study adresses this problem by investigating solutions for an enhanced multifiber beam element, accounting for vertical stretching of the cross-section occurring due to the presence of stirrups. A timoshenko beam element with internal degrees of freedom and higher order interpolation functions is selected. Full 3D stresses and strains are obtained and the construction of the element and sectional stiffness matrices is detailed. The element presented hereafter is suitable for an arbitrary shape cross-section made of heterogeneous materials. Numerical applications on a plain concrete cantilever beam subjected to tension and bending tests respectively are presented. Moreover, as a first application, a dilation effect is added to the concrete fibers in order to highlight the role of transversal rebars. All the numerical results are confronted to the outcomes of stantard 3D finite element computations.
Nucleation and Atmospheric Aerosols, 2017
This research is to investigate the behaviour of overbalanced High Strength Reinforced Concrete Beams with the compression zone confined with spiral / helical steel reinforcements. The study covered beam behaviour with respect to flexural strength, shear strength, deflection and cracking related to confined concrete. Six 200mm (width) X 300mm (depth) X 3000mm (length) Reinforced Concrete (RC) Beams, the first three beams incorporating steel ratio of 1.42ρb and the remaining 1.64ρb were tested under a four point static load test. The confinement of the concrete was carried out using spiral reinforcements of diameter 6mm and yield stress of 406N/mm2 with pitches of 50mm and 100mm. Measurements of deflection, cracking, and strains on both main reinforcements and concrete of the beams were taken. At the same level of stress, beams with confined concrete strained less than control beams without confinement for both tensile strain at the main steel reinforcement and compressive strain across the compression zone of concrete. Deflections of beams with helical confinement were less than the control beams.All beams failed in shear / flexural mode and gave fair warning against failure, more specifically beams with 1.42ρb, which is not normally associated with shear-type failure of beams which are over reinforced. The early shear failure prevented the beams from achieving its full utilisation of the ultimate strength. It is recommended that for over-reinforced confined concrete beams, the shear strength of beams should be based on using the diagonal compressive strut angle (θ) of more than 22 degrees recommended in Eurocode 2 (EC2), hence giving the beam higher safety factor against shear failure. All samples exhibited flexure and shear cracks in a manner which gave a good warning against failure. The ratio of the failure load to the theoretical ultimate load for shear ranged between 0.98 and 1.25 while the ratio of the failure load to the ultimate flexural load ranged between 1.00 and 1.25. Because of the early shear failure, the effects of spiral spacing could not be well identified.