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Download file# A new method for modelling reinforcement and bond in finite element analysis of reinforced concrete

thesis

posted on 18.10.2010, 13:34 authored by Abdullah A. BajarwanIn conventional finite element analysis of reinforced concrete the
steel bars are normally assumed to lie along the concrete element
edges and very often the bond gripping the steel to the concrete is
assumed to be infinitely stiff. The first assumption makes it
difficult to model all steel bars leading to the inclusion of only a
few representative bars. Shear reinforcement is usually ignored.
Thin concrete cover also creates difficulty by causing long thin
finite elements in that region. The second assumption does not
reflect the true behaviour of the system.
In this research a new method for the modelling of steel in
reinforced concrete by finite element analysis has been developed
which allows all steel reinforcement to be included in the
analysis. The method is based on modelling the steel and concrete
separately, the two materials being interconnected by the bond
forces between them. Thus, bond stiffness is naturally included in
the analysis. Such interconnection of steel and concrete is
achieved by an interface bond matrix which is derived from the
relative displacements between the steel and the concrete at the
steel nodes. A linear bond slip relation is assumed for the bond,
and a linear stress strain relation is assumed for the concrete and
the steel. The work has extended also to nonlinear bond stress-slip
relation. Concrete is represented by 8-noded isoparametric
quadrilateral elements, and the steel is represented by two noded
bar elements. The bond is represented by springs joining each steel
node to all 8-concrete nodes.
The solution of the resulting system of equations is achieved in
an iterative manner which converges quite rapidly, and which
requires less computation than the direct solution needs.
Three types of problems are analysed in two dimension to
demonstrate the application of this new method. These are beam,
cantilever and pullout problems. The first two, being real
problems, demonstrate the ability of the method to handle complex
steel arrangements, thin concrete covers and anchorage of steel,
while the third problem shows the application of load to the steel
rather than to the concrete. Concrete and steel deformations and
stresses are calculated at their nodes. Bond stresses are given at
all steel nodes. In the nonlinear bond analysis, deterioration of
bond will be demonstrated in pullout and pushout tests at high
loads.

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## School

- Architecture, Building and Civil Engineering