Experimental studies on strength and ductility of CFRP jacketed...
reinforced concrete beam-column joints
Varinder Singh a,⇑, Prem Pal Bansal b, Maneek Kumar b, S.K. Kaushik c
a Department of Civil Engineering, Jan Nayak Ch. Devi Lal Memorial College of Engineering, Sirsa 125 055, India
b Department of Civil Engineering, Thapar University, Patiala 147 004, India
c Department of Civil Engineering, Indian Institute of Technology, Roorkee, Roorkee 247 667, India
a b s t r a c t
Beam-column joints in reinforced concrete (RC) framed structures are recognized as most vulnerable
structural element subjected to lateral loads. The use of various jacketing techniques for strengthening
or retrofitting the existing structural components is very frequent. In the present work, the effect on
the strength of beam-column joints initially stressed to three different stress levels, retrofitted with CFRP
jackets has been presented. A total of 9 RC beam-column joints were tested under static loading conditions.
CFRP strengthening has been carried out for beam-column joints already stressed to three different
stress levels. The jackets have been provided in L-shape and at 45 orientation to the joint in two layers.
The results show improvement in the ultimate load carrying capacity (7–12%) of the retrofitted beams,
when compared to the control beams along with an increase of 15% in yield load for each of such exterior
beam- column joints. Stiffness up to the first crack load was 17.36% and 26.94% more for stress level-2
and stress level-3 as compared to stress level-1.
Performance enhancement of R/C building columns and beamcolumn joints
through shotcrete jacketing
Alexander-Dimitrios G. Tsonos
Laboratory of Reinforced Concrete and Masonry Structures, Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
a b s t r a c t
This paper investigates the effectiveness and suitability of shotcrete and cast-in-place concrete as
means of retrofitting columns and beamcolumn joints in reinforced concrete frame structures, so as to
improve their shear and/or flexural performance. Thus, the use of four-sided and two-sided reinforced
shotcrete or cast-in-place concrete jackets has been investigated experimentally for the case of preearthquake
retrofitting of columns and beamcolumn joints. Focus has been placed on studying their
lateral performance and on comparing the effectiveness of the reinforced shotcrete jackets with reference
to the corresponding cast-in-place ones, as well as that of the two-sided jackets with reference to
the corresponding four-sided ones. All types of concrete jackets examined were found to be equally
satisfactory in their ability to strengthen existing old frame structures.
' 2009 Elsevier Ltd. All rights reserved.
Seismic performance evaluation of multi-column bridge bents retrofitted
with different alternatives using incremental dynamic analysis
A.H.M. Muntasir Billah, M. Shahria Alam
a b s t r a c t
A comprehensive study has been carried out to numerically investigate the performance of a three column
bridge bent retrofitted with different options. The bridge bent represents a typical case of vulnerable
bridges since it was built in the early sixties with minimal seismic design requirements. This study evaluates
four different retrofitting provisions, namely carbon fiber reinforced polymer (CFRP) jacketing, steel
jacketing, concrete jacketing, and engineered cementitious composite (ECC) jacketing for improving the
seismic performance of this non-seismically designed bridge bent. Finite element methods have been
implemented in this study where each retrofitting technique has been modeled and numerically validated
with the experimental results. Analytical models of those retrofitted bridge bents have been developed
using finite element analysis tools and verified against experimental results. Nonlinear static
pushover analyses have been performed to compare their performances in terms of performance criteria
such as the displacement and base shear at cracking, yielding, and crushing. Incremental dynamic time
history analyses have been performed to assess the dynamic behavior of the retrofitted bents and to generate
required data for performance-based evaluations. The performance-based assessment study
employed 20 near fault ground motions to compare the performance of these retrofitting strategies in
terms of maximum drift (%), residual drift, and ductility demand. The results indicated that both the CFRP
and ECC jacketing were effective in reducing the anticipated damage of the retrofitted bridge bent.
2014 Elsevier Ltd. All rights reserved
Experimental study of RC beam–column joints strengthened using CFRP composites
Kien Le-Trung a, Kihak Lee a,*, Jaehong Lee a,1, Do Hyung Lee b,2, Sungwoo Wooc,3
a b s t r a c t
This paper presents an experimental study to strengthen the shear capacity of non-seismic joints using
Carbon Fiber Reinforced Plastic (CFRP) materials. Eight exterior RC beam–column joint specimens including
a non-seismic specimen, a seismic specimen and six retrofitted specimens with different configurations
of CFRP sheets were developed and tested to find out an effective way to improve the seismic
performance of the joints in terms of the lateral strength and ductility. The different configurations of
CFRP sheets considered were the T-shape, L-shape, X-shape and strip combinations. The research focused
on the effect of using CFRP sheets for enhancing strength and increasing ductility of the non-seismic
beam–column joints. The test results showed that appropriately adding CFRP composites to the non-seismic
specimen significantly improved the lateral strength as well ductility of the test specimens. Especially,
the X-shaped configuration of wrapping, the strips on the column and two layers of the CFRP
sheets resulted in a better performance in terms of ductility and strength.
2009 Elsevier Ltd. All rights reserved.
Evaluation of the performance of a sliding-type base isolation system with a NiTi
shape memory alloy device considering temperature effects
Osman E. Ozbulut, Stefan Hurlebaus
a b s t r a c t
This paper investigates the seismic performance of a sliding-type base isolation system considering
environmental temperature changes. The isolation system consists of a steelTeflon sliding bearing that
carries the vertical loads and dissipates energy as a result of its frictional behavior and a shape memory
alloy (SMA) device that provides re-centering force and additional damping. A five-span continuous bridge
is modeled with sliding bearings and an SMA device as a two-degree-of-freedom system. A neuro-fuzzy
model that is capable of capturing the material response at different temperatures and loading frequencies
is used to predict the force at superelastic NiTi shape memory alloy wires. The design parameters of the
SMA device, i.e., the length and cross-sectional area of NiTi wires, are obtained through a multi-objective
genetic algorithm optimization process. A time-domain method that uses wavelet operations for the
matching of an accelerogram to the pseudo-acceleration or displacement ordinates for a given design
spectrum is employed to generate ground motion records used in the simulations. Finally, nonlinear time
history analyses of the isolated bridge are conducted for outside temperatures of 0 C, 20 C and 40 C. The
results show that a sliding-type isolation system with an SMA re-centering device can effectively reduce
the seismic response of bridges for each temperature considered in the study.
' 2009 Elsevier Ltd. All rights reserved.
Development of corrosion-free concrete beamcolumn joint with adequate
seismic energy dissipation
M. Nehdia,, M. Shahria Alamb, M.A. Youssef a
a b s t r a c t
The use of Fibre-Reinforced Polymer (FRP) as reinforcement in concrete structures has received much
attention owing to its higher resistance to corrosion compared to that of regular steel reinforcement.
Since FRP is a brittle material, its use in seismic resisting structural elements has been a concern. FRP
RC structures can be made ductile by utilizing a ductile material such as steel at the plastic hinge
regions. However, the use of steel negates the corrosion resistance purpose of FRP. On the other hand,
NickelTitanium (NiTi) shape memory alloy (SMA) is highly resistant to corrosion. It also brings about
an added advantage in seismic regions since it has the unique ability to undergo large deformation, but can
regain its undeformed shape through stress removal. In this study, a SMAFRP hybrid RC beamcolumn
joint has been proposed to address not only corrosion resistance, but also seismic related problems. This
joint is reinforced with a super-elastic NiTi SMA bar at the plastic hinge regions of the beam and FRP in
the other regions of the beam and column. To validate the proposed joint, an experimental investigation
has been carried out to develop such a joint and test it under reversed cyclic loading. The results are
compared in terms of loadstorey drift, momentrotation and energy dissipation capacity to those of a
similar RC beamcolumn joint specimen reinforced with conventional steel. The SMAFRP beamcolumn
joint proved to have adequate energy dissipation under earthquake type loading.
' 2010 Elsevier Ltd. All rights reserved.
Study of the seismic behavior of external RC beam–column joints
through experimental tests and numerical simulations
Angelo Masi a,1, Giuseppe Santarsiero a,⇑, Gian Piero Lignola b,2, Gerardo M. Verderame
a b s t r a c t
The paper is focused on the analysis of some test results obtained in the framework of a wide experimental
program on RC beam–column joints carried out at the Laboratory of Structures of the University of
Basilicata in Potenza, Italy. Specifically, cyclic tests on full-scale joint specimens having different earthquake
resistant design levels were performed, applying different values of axial force. Test results relevant
to 4 specimens have been analyzed and compared with the results of numerical simulations
based on an accurate finite element modeling using the DIANA code at the Structural Engineering Dept.
of the University of Naples. Experimental results show how the value of the axial load acting on the column
can change the collapse mode, spreading damage from the beam to the joint panel. Moreover, a collapse
mode due to the failure of beam longitudinal rebars, sometimes neglected in structural codes, has
been observed. Numerical simulations were used to evaluate the stress distribution in the joint panel as a
function of the axial load and to quantify the beam rebar deformations. The reasons for the specimens’
global failure and, specifically, for that of the beam longitudinal rebars were identified and highlighted
through a comparison with the experimental results.
2013 Elsevier Ltd. All rights reserved.
Experimental investigation on reinforced concrete interior
beam–column joints rehabilitated by ferrocement jackets
Bo Li a, Eddie Siu-shu Lam a,⇑, Bo Wub, Ya-yong Wang
a b s t r a c t
In this study, a method for rehabilitating reinforced concrete interior beam–column joints using ferrocement
jackets with embedded diagonal reinforcements is proposed. It improves seismic performance of
substandard beam–column joints and repairs deteriorated concrete cover without increasing the dimensions
of the joints. Ferrocement, comprising mortar and wire mesh, was applied to replace concrete cover
to enhance shear strength of the joints. Diagonal reinforcements were installed to reduce the forces transferred
to the joint core. Four 2/3 scale interior beam–column joints, including one control specimen and
three strengthened specimens, were prepared and tested under quasi-static cyclic loading. Three types of
mortars were considered for each strengthened specimen. Test results have indicated that the proposed
rehabilitation method can improve seismic performance of interior beam–column joints using ferrocement
with high strength mortar. Strength of mortar is the vital factor affecting the performance of
strengthened specimens. Anchor bolts installed at the interface between ferrocement and concrete substrate
improve bonding and overall performance. Finally, a method for predicting the shear strength of
joints rehabilitated by ferrocement jackets with embedded diagonal reinforcements is proposed.
2013 Elsevier Ltd. All rights reserved.
