الفهرس 
BEAM-COLUMN JOINT’S FAILURE MODESOnly 14 pages are availabe for public view
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Abstract
This thesis represents an experimental-analytical investigation in the
flexural behavior of CFRP strengthened RC beam-column joints. The study
aims at investigating the effect of using CFRP sheets to strengthen the
hogging beam’s portion adjacent to the column, on both the flexural
capacity and ductility of the beam-column joint.
The key parameters of this study including the internal steel reinforcement
detailing within the joint’s region and the length of the CFRP strengthening
sheets, are first investigated experimentally. Accordingly, six medium-scale
specimens are statically tested. These specimens are divided into two
groups (Pix and P2x) with a middle steel bars or bent bars in the joint’s
region, respectively. In addition, each group consists of three specimens;
one control and two strengthened with CFRP sheets having 100mm and
650mm length, respectively. The key test results first demonstrated that
providing bent bars in the joint’s area is useful in restraining the joint’s
rotation and minimizing the accompanying beam’s deflection as well as the
cracks in the joint’s area. The key test results also demonstrate that longer
sheets result in higher flexural capacity enhancement compared to shorter ones, but at the pnce of dramatically reduced ductility. Furthermore,
shorter sheets are demonstrated advantageous in initiating a ductile flexural
failure mode of the specimen, through the yielding of the beam’s top steel
at the sheet’s end (further away from the column’s face). The latter
phenomena totally vanish with longer sheets until flexural compression
failure occurs at the column’s face, hence, resulting in a brittle failure
mode.
The experimental study is then extended analytically using the non-linear
finite element package [ATENA]. The analytical model is first validated
through comparisons with test results. The model is then used to conduct a
parametric study investigating a wider range of parameters than those
investigated experimentally, as well as new parameters not considered in
the tests. In this respect, three parameters are discussed. The first parameter
is the hogging CFRP strengthened beam’s length, I, while the second one is
the concrete grade, !cu. Finally, the number of CFRP strengthening layers,
n, is investigated. A minimum sheets’ length is first established, Imin,
resulting In maxunum capacity enhancement accompanied with
comparable ductility to the control specimen, induced by the steel yielding
initiated in the beam at the sheets’ end at considerably lower loads than the
flexural capacity. Longer sheets are found to reduce ductility at no further
increase in capacity, up to a critical length, Ie, where ductility is totally lost.
In addition, higher concrete grades increase the two previous limits (best-fit
equations are established) as well as the safe application margin in between
and result in higher efficiency of the strengthening system. However, full
activation of the sheets is found not possible in high-strength-concrete; due
to the premature damage of the column, in line with the ACI 440-02
strengthening limits. Finally, a maximum number of three CFRP layers are
established for optimum efficiency. Nonetheless, the major enhancements
occur at one layer.