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PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
A Finite Element Analysis of Damaged Reinforced Concrete Beams Retrofitted with Fibrous Concrete
W.B. Almajed and R.Y. Xiao
Civil and Computational Engineering Centre, School of Engineering, University of Wales Swansea, United Kingdom
W.B. Almajed, R.Y. Xiao, "A Finite Element Analysis of Damaged Reinforced Concrete Beams Retrofitted with Fibrous Concrete", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 4, 2006. doi:10.4203/ccp.83.4
Keywords: concrete structural analysis, finite element analysis, ANSYS, non-linear analysis, retrofitted concrete beam, fibrous concrete, composite structures.
The traditional method of designing and analysing reinforced concrete has matured by the development of finite elements and by use of computers has had a significant impact on complex systems analysis in a practical way . There is much finite element analysis software available which has a wide range of stress analysis applications. However, simulating the behaviour of reinforced concrete and modelling its properties are difficult for finite element analysis software due to the complexity of the concrete composite . In addition, the constitutive equations which can describe the basic behaviour and characteristics of reinforced concrete materials may not exist in most finite element software applications .
Laboratory investigations can offer detailed physical understanding in the behaviour of concrete structure. However, the process is expensive and time consuming, thus, nonlinear finite element modelling and analysis methods have been developed to predict the behaviour of concrete structures similar to laboratory work.
Nonlinear models of reinforced concrete beams for shear failure simulation and nonlinear models of reinforced concrete beams for flexural failure simulation were set for this numerical analysis investigation by using ANSYS. All models were compared with data that were collected from the laboratory work.
A discrete element  model and smeared material  model have been employed in this investigation. The smeared material model will be adopted to model concrete by using the material properties of concrete to be smeared throughout the concrete element and discrete element modelling will be used to model steel reinforcement. The simplified design stress-strain curve has been used to model the concrete material and a modification of the stress-strain curve for smeared material has been adopted to simulate the load deflection behaviour of real beams. All properties were applied according to BS 8110.
The results show that a significant matching in compressive stresses was obtained on the top of beams with an average percentage difference of 5.09% and 10.05% for beams with shear and flexure failure respectively. On the other hand, insignificant matching results were observed for the tensile strength of beams with shear failure, the average of percentage difference of 38.74% was obtained. Some of beams have experienced a trivial tensile strength in the bottom due to the shear failure. Conversely, the beams with flexure failure have obtained a slightly significant matching results in tensile strength with average of percentage difference of 24.23% due to compressive failure.
In beams with shear failure, large spacing between the vertical shear links has been used, which produced lower failure loads with a relatively lower shear stresses that lead to shear failure. On the other hand, shorter spacing has been used in beams with flexure failure, which produced higher failure loads with relatively higher shear stresses. However, stresses were controlled by shear links.
Similar cracking and crushing patterns and locations have been observed in the finite element simulation compared to the real beams. Crushing occurred in top of most beams. For shear failure beams, crushing occurred outside the two points load, while in flexure failure beams, crushing should occur inside the two points load.
The modified stress-strain curve of smeared concrete material has presented significant load-deflection behaviour for both beam failures. The elastic and plastic behaviour of load-deflection curve in beam with flexural failure were perfectly matched, and the elastic behaviour of beam with shear failure was simulated significantly.
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