The economic and time constraints in the repair or upgrading of existing infrastructure have become a major issue, particularly
extending the service lifespan of bridges. Fibre reinforced polymer (FRP) has shown great promise as a state-of-the-art material in flex-
ural and shear strengthening as external reinforcement. However, little attention has been paid to torsional strengthening in terms of
both experimental and numerical research. This paper focuses on the bond-behaviour of externally bonded CFRP in an overall inves-
tigation of torsional strengthening of solid and box-section reinforced concrete beams. Significant levels of debonding prior to failure by
CFRP rupture were measured in experiments with photogrammetry. Numerical work was carried out using non-linear finite element
(FE) modelling. Good agreement in terms of torque-twist behaviour, steel and CFRP reinforcement responses, and crack patterns
was achieved. The addition of a bond-slip model between the CFRP reinforcement and concrete meant that the debonding mechanisms
prior to and unique failure modes of all the specimens were modelled correctly as well. 6883
 2006 Elsevier Ltd. All rights reserved.1. Introduction
The bridging infrastructure in developed countries has
matured considerably over the last century. However,
increased traffic volumes and loads, diminished capacity
through environmental degradation and age, more strin-
gent updates to design code regulations, and the need for
seismic retrofit in some parts of the world have necessitated
the need for repair and rehabilitation of existing infrastruc-
ture. Many building and bridge elements are subjected to
significant equilibrium torsional moments that may require
strengthening. The use and research of externally bonded
FRP is relatively advanced in flexural and shear strength-
ening. In comparison, relatively little is known about tor-
sional strengthening. A good example of this is theWestgate Bridge in Melbourne, Australia [1]. Without suf-
ficient information, shear strengthening guidelines had to
be adapted for torsional design. In a literature survey con-
ducted by the authors [2], no experimental data was found
before 2001. Several torsional strengthening investigations
of exploratory nature have been conducted since then [3,4].
This paper attempts to address the gap in knowledge in this
area.
In this study, six CFRP strengthened medium-scale thin-
walled box-section and solid reinforced concrete (RC)
beams were investigated. The focus in this paper is on the
bond-behaviour of the externally bonded CFRP, which is
the first known study for torsional strengthening. A more
detailed discussion on the other aspects of the experiments
can be found in Hii and Al-Mahaidi [2]. The bond behav-
iour was quantified using photogrammetry measurements
in experiments. A bond-slip model was introduced into
non-linear finite element modelling to further investigate
this aspect in detail.2. Experimental program
2.1. Specimen details and experimental setup
Six RC beams of 500 · 350 mm deep cross-section and
2500 mm long were constructed for this test (Fig. 1). Two
specimens were solid sections (CS1, FS050D2) while the
rest were box-sections. A summary of the specimen details
can be found in Table 1, along with the average concrete
compressive strength of cores extracted. The reinforcement
layout was designed for minimum torsional capacity [5] to
simulate a box-girder that was now torsionally deficient.
The stirrups were spaced at 125 mm centres in the test zone
for all the beams.
For this investigation, MBrace CF130 CFRP sheets and
epoxy resins [6] were externally bonded using the wet lay-
up method. The fibre modulus and thickness of the sheet 钢筋混凝土桥梁英文文献和中文翻译:http://www.youerw.com/fanyi/lunwen_4466.html