STRUCTURAL RETROFITTING OF CONCRETE BEAMS USING FRP - Debonding Issues
(2011) In TVSM-1000- 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... (More) - 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. (Less) - Abstract (Swedish)
- Popular Abstract in English
Concrete is one of our most common building materials and is used both for buildings,
bridges and other heavy structures. Typically, concrete structures are very durable, but
sometimes they need to be strengthened. The reason may be cracking due to environmental
effects, that a bridge is to be used for heavier traffic, new building codes, or damage resulting
from earthquakes.
Concrete is a material that can withstand compressive loads very well but is sensitive to
tensile forces. Therefore, concrete structures are typically reinforced by casting in steel bars in
areas where tension can arise. This cannot be done afterwards, and one... (More) - Popular Abstract in English
Concrete is one of our most common building materials and is used both for buildings,
bridges and other heavy structures. Typically, concrete structures are very durable, but
sometimes they need to be strengthened. The reason may be cracking due to environmental
effects, that a bridge is to be used for heavier traffic, new building codes, or damage resulting
from earthquakes.
Concrete is a material that can withstand compressive loads very well but is sensitive to
tensile forces. Therefore, concrete structures are typically reinforced by casting in steel bars in
areas where tension can arise. This cannot be done afterwards, and one strengthening method,
is therefore to glue reinforcement on the exterior of the structure in the areas exposed to
tension.
Fibre composite can be used in reinforcing concrete structures externally. Fibre composite
materials have low density, can be easily installed and are easy to cut to length on site.
Therefore, fibre composite as external reinforcement for concrete structures has become very
attractive and popular around the world.
It is important to understand the behaviour of a strengthened structure well and realize
what parameters affect the failure mode and load-bearing capacity. The aim of this thesis is
therefore to investigate and improve the understanding of the behaviour of reinforced concrete
beams strengthened with fibre composite.
These structures have a critical problem implying that they may fail in a sudden manner.
This failure involves separation between composite and concrete. Special attention is paid to
this phenomenon, which is called debonding.
One scope of this study was to develop computer modelling framework. Therefore, three
dimensional computations were conducted considering the nonlinear behaviour of the
materials. A new model for the concrete-fibre composite interface was included.
The computations were verified against experiments. The results confirmed the ability of
the computations to recreate the load-deflection behaviour, the crack distribution, and the
failure modes. Simulations and experiments showed that application of fibre composite can
increase the load capacity and the stiffness of the beams.
The influence of several parameters such as length and width of fibre composite and
properties of adhesive were investigated. Large width and length of fibre composite and soft
adhesive would yield to reduce tendency of debonding and increase thus of the utilization of
fibre composite and increase load capacity.
The findings from this study yield a proposal for a modification of design code rules. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/2203666
- author
- Obaidat, Yasmeen LU
- supervisor
-
- Ola Dahlblom LU
- Susanne Heyden LU
- opponent
-
- Prof. Täljsten, Björn, Luleå tekniska universitet, Luleå
- organization
- publishing date
- 2011-11
- type
- Thesis
- publication status
- published
- subject
- in
- TVSM-1000
- issue
- TVSM-1023
- pages
- 163 pages
- publisher
- Department of Construction Sciences, Lund University
- defense location
- Lecture hall V:C, V-building, John Ericssons väg 1, Lund University Faculty of Engineering
- defense date
- 2011-12-06 10:15:00
- ISSN
- 0281-6679
- ISBN
- 978-91-7473-194-1
- language
- English
- LU publication?
- yes
- id
- e731ca6b-e517-4e8d-9a83-4fde23a310a0 (old id 2203666)
- date added to LUP
- 2016-04-01 12:56:44
- date last changed
- 2023-10-16 09:23:46
@phdthesis{e731ca6b-e517-4e8d-9a83-4fde23a310a0, abstract = {{A 3D nonlinear finite element analysis modelling framework was developed for simulating<br/><br> the behaviour of beams retrofitted with fibre reinforced polymer (FRP). The ABAQUS<br/><br> program was used for this purpose. Concrete was modelled using a plastic damage model.<br/><br> Steel bars were modelled as an elastic perfectly plastic material, with perfect bond between<br/><br> concrete and steel. A cohesive model was used for modelling the FRP-concrete interface.<br/><br> Bond properties needed as input to the cohesive model, such as initial stiffness, shear strength<br/><br> and fracture energy were proposed based on fitting FEM results to experimental results from<br/><br> literature. Initial stiffness was related to the adhesive properties. Shear strength and fracture<br/><br> energy were expressed as functions of tensile strength of concrete and of adhesive properties.<br/><br> Experimental tests were performed to investigate the behaviour of retrofitted beams. The<br/><br> model was verified through comparison with the experimental data regarding failure mode<br/><br> and load-displacement behaviour.<br/><br> The influence of several parameters such as length and width of FRP and properties of the<br/><br> adhesive were investigated. The result showed that when the length of FRP increases, the load<br/><br> capacity of the beam increases for both shear and flexural strengthening. The result also<br/><br> showed that the FRP to concrete width ratio and the stiffness of FRP affect the failure mode<br/><br> of retrofitted beams. The maximum load increases with increased width ratio. Increased FRP<br/><br> stiffness increases the maximum load only up to a certain value of the stiffness, and thereafter<br/><br> the maximum load decreases. The maximum load also increases when the stiffness of<br/><br> adhesive decreases.<br/><br> An improvement of the calculation of interfacial shear stress at plate end in a design rule<br/><br> for simply supported beams bonded with FRP was proposed. The proposed design rule was<br/><br> applied to an existing defective beam and the result was verified using the FEM model.}}, author = {{Obaidat, Yasmeen}}, isbn = {{978-91-7473-194-1}}, issn = {{0281-6679}}, language = {{eng}}, number = {{TVSM-1023}}, publisher = {{Department of Construction Sciences, Lund University}}, school = {{Lund University}}, series = {{TVSM-1000}}, title = {{STRUCTURAL RETROFITTING OF CONCRETE BEAMS USING FRP - Debonding Issues}}, url = {{https://lup.lub.lu.se/search/files/3060710/2203686.pdf}}, year = {{2011}}, }