02-02-2013, 12:08 PM
FLEXURAL BEHAVIOR OF REINFORCED CONCRETE BEAMS USING FINITE ELEMENT ANALYSIS (ELASTIC ANALYSIS)
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Abstract.
Concrete structural components exist in buildings in different forms.
Understanding the response of these components during loading is crucial to the
development of an overall efficient and safe structure. Different methods have been
utilized to study the response of structural components. Experimental based testing has
been widely used as a means to analyse individual elements and the effects of concrete
strength under loading. While this is a method that produces real life response, it is
extremely time consuming, and the use of materials can be quite costly. The use of finite
element analysis to study these components has also been used.
The performed study investigation attempts to compare the results from elastic
analysis of a reinforced beam under transverse loading, using an analysis software
package to that obtained from a normal theoretical analysis.
Introduction
A concrete beam is a structural element that carries load primarily in
bending. Bending causes a beam to go into compression and tension. Beams
generally carry vertical gravitational forces but can also be used to carry
horizontal loads. The loads carried by a beam are transferred to columns, walls,
which is then transferred to foundations. The compression section must be
designed to resist buckling and crushing, while the tension section must be able
to adequately resist to the tension. Experimental based testing has been widely
used as a means to analyse individual elements and the effects of concrete
strength under loading. While this is a method that produces real life response.
Finite Element Modeling of Reinforced Concrete Beam
Finite Element Analysis (FEA) represents a numerical method, which
provides solution to problems that would otherwise be difficult to obtain. The
numerical analysis investigations were performed with commercial software
ANSYS. This software is a suite of powerful engineering simulation programs,
based on finite element method, which can solve problems ranging from
relatively simpler linear analyses to the most challenging non-linear
simulations. The analysis of a structure with ANSYS is performed in three
stages
a) Pre-processing P – defining the finite element model and environmental
factors to be applied to it.
b) Analysis solver – solution of finite element model.
c) Post-processing of results like defomations, contours for displacement,
etc., using visualization tools.
Advances in the field of computer-aided engineering during the last
two decades have been quite extensive and have led to considerable benefits to
many engineering industries. In the building industry, use of advanced finite
element tools not only allowed the introduction of innovative and efficient
building products, but also the development of accurate design methods. Here
SOLID65 and LINK8 elements are used to model RC and LRC beams.
Features of these elements are given here and details of the model used in the
paper are given in next section.
Calibration Model
A RCC beam with two point loading case was taken for analysis as
shown in the Fig. 1, with: size of the reinforced concrete beam – 100 × 150 mm;
size of loading and support steel plates – 100 × 100 mm, 6 mm thick; steel
reinforcement details: 3 rebars of 12 mm dia at bottom, 2 rebars of 8 mm dia at
top, stirrups of 2 legged 6 mm dia at 100 mm c/c.
Element Types
The Solid65 element was used to model the concrete. This element has
eight nodes with three degrees of freedom at each node – translations in the
nodal x-, y-, and z-directions. This element is capable of plastic deformation,
cracking in three orthogonal directions, and crushing. A schematic of the
element is shown in Fig. 4.
Meshing
For Solid65 element the mesh was set up such that square or rectangular
elements were created. The volume sweep command was used to mesh the steel
plate. This properly sets the width and length of elements in the plates to be
consistent with the elements and nodes in the concrete portions of the model.
The necessary element divisions are noted. The meshing of the reinforcement is
a special case compared to the volumes. The reinforcement model was meshed
using line elements so that the nodes of the line elements come exactly over the
node of the solid elements which are later merged so that both rebar elements
and the concrete elements share the same nodes.