STRUCTURAL RETROFITTING OF CONCRETE BEAMS USING FRP - Debonding Issues

Yasmeen Obaidat

Research output: ThesisDoctoral Thesis (compilation)

Abstract

A 3D nonlinear finite element analysis modelling framework was developed for simulating
the behaviour of beams retrofitted with fibre reinforced polymer (FRP). The ABAQUS
program was used for this purpose. Concrete was modelled using a plastic damage model.
Steel bars were modelled as an elastic perfectly plastic material, with perfect bond between
concrete and steel. A cohesive model was used for modelling the FRP-concrete interface.
Bond properties needed as input to the cohesive model, such as initial stiffness, shear strength
and fracture energy were proposed based on fitting FEM results to experimental results from
literature. Initial stiffness was related to the adhesive properties. Shear strength and fracture
energy were expressed as functions of tensile strength of concrete and of adhesive properties.
Experimental tests were performed to investigate the behaviour of retrofitted beams. The
model was verified through comparison with the experimental data regarding failure mode
and load-displacement behaviour.
The influence of several parameters such as length and width of FRP and properties of the
adhesive were investigated. The result showed that when the length of FRP increases, the load
capacity of the beam increases for both shear and flexural strengthening. The result also
showed that the FRP to concrete width ratio and the stiffness of FRP affect the failure mode
of retrofitted beams. The maximum load increases with increased width ratio. Increased FRP
stiffness increases the maximum load only up to a certain value of the stiffness, and thereafter
the maximum load decreases. The maximum load also increases when the stiffness of
adhesive decreases.
An improvement of the calculation of interfacial shear stress at plate end in a design rule
for simply supported beams bonded with FRP was proposed. The proposed design rule was
applied to an existing defective beam and the result was verified using the FEM model.
Original languageEnglish
QualificationDoctor
Awarding Institution
  • Structural Mechanics
Supervisors/Advisors
  • Dahlblom, Ola, Supervisor
  • Heyden, Susanne, Supervisor
Award date2011 Dec 6
Publisher
Print ISBNs978-91-7473-194-1
Publication statusPublished - 2011

Bibliographical note

Defence details

Date: 2011-12-06
Time: 10:15
Place: Lecture hall V:C, V-building, John Ericssons väg 1, Lund University Faculty of Engineering

External reviewer(s)

Name: Täljsten, Björn
Title: Prof.
Affiliation: Luleå tekniska universitet, Luleå

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Subject classification (UKÄ)

  • Mechanical Engineering

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