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|Title: ||Computational modeling, experimental and theoretical study on bond behaviors of hybrid-bonded FRP strengthened concrete structures|
|Other Titles: ||Hun he zhan jie xian wei zeng qiang ju he cai liao jia gu hun ning tu jie gou zhan jie mian de ji suan mo xing, shi yan ji li lun yan jiu|
|Authors: ||Liu, Kang ( 劉康)|
|Department: ||Department of Building and Construction|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2011|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Reinforced concrete construction.|
|Notes: ||CityU Call Number: TA683.2 .L58 2011|
xxv, 238 leaves : ill. 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2011.
Includes bibliographical references (leaves 220-238)
|Abstract: ||External bonding of fiber-reinforced polymer (FRP) to reinforced concrete members
has become a popular method of retrofitting/strengthening concrete structures in
recent years. This technology allows the high tensile strength of FRP to be transmitted
to concrete structures through surface adhesion. However, surface adhesion between
FRP and concrete is known to be weak and unreliable; it offers poor bonding between
the FRP and the concrete members and often induces premature debonding at the
bond interface. Such premature debonding has greatly reduced the usage rate of FRP.
To solve this problem, the author's supervisor has developed a new technology,
namely, the hybrid bonded FRP (HB-FRP), that combines adhesive bonding with
In this research, the mechanism of the HB-FRP system was studied by using FE
analysis; a FE model for HB-FRP strengthened beams was developed to simulate the
responses of the new structural system. Bond behaviors for externally bonded FRP
(EB-FRP) and HB-FRP joints were experimentally investigated by employing the
single shear pull-off test on ten EB-FRP and HB-FRP specimens with different bond
lengths. Based on the analytical bond-slip model for HB-FRP joints proposed in this
work, bond behaviors of adhesive and HB-FRP joints were studied theoretically.
Based on the experimental results, performance of the proposed bond-slip model for
HB-FRP joints was verified. Finally, a standard test protocol for HB-FRP joints was
established for design purposes.
An FE model for numerical simulation of the HB-FRP strengthened beam under
static loading is developed to study the mechanism of the HB-FRP system. A
combination of the shear friction model with the traditional bond-slip model for the
adhesive bond interface and the dowel model for dowel action of concrete nails render
structural analysis of the very complicated HB-FRP strengthening scheme feasible.
The FE model is valid and capable of studying the debonding mechanism and the
failure mode, and of simulating overall responses of the complicated structural system.
Mechanical fasteners alter the failure mechanism from adhesive debonding to pull-out
failure of mechanical fasteners, which increases the interfacial bond and the load
carrying capacity of the beam, and results in better use of strength of the FRP strip.
The frictional shear resistance caused by mechanical fasteners can be several times
greater than the adhesive bond strength. The additional frictional resistance depends
on the pull-out resistance of the anchors and on the number and spacing of mechanical
The single shear pull-off test was employed on ten EB-FRP and HB-FRP
specimens with different bond lengths. The test results indicate the importance of
careful specimen preparation as the failure mode can be significantly affected. In
addition to further verification of effectiveness on HB-FRP system, test results were
used to verify the new proposed analytical bond-slip model for HB-FRP joints.
Adopting the bond-slip relationship for adhesive joints proposed by Zhou et al.,
the local bond-slip relationship for HB-FRP joints is developed by superimposing
three mechanisms in the HB-FRP system. Theoretical relationship between the pull-off load and the slip at the free and loaded end for HB-FRP joints is obtained by
homogenizing the bond behavior induced by the mechanical mechanism. Expressions
for load capacity are theoretically established for adhesive and homogenized HB-FRP
joints with an infinite bond length.
Based on the indirect analytical method, identification procedures were developed
to calibrate the parameters in the proposed bond-slip model for HB-FRP joints. The
unknown parameters were determined by computational minimization of the
difference between experimental and theoretical results. Adopting the identified
parameters, good performances of the proposed bond-slip models for EB-FRP and
HB-FRP joints were obtained by comparison between numerical and experimental
results. The calibrated models were then used to calculate the load capacity and the
effective bond length for the particular EB-FRP and HB-FRP joints. Finally, a
standard test protocol for HB-FRP joints was proposed for design purposes.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b4086372|
|Appears in Collections:||BC - Doctor of Philosophy |
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