Dynamic Analysis of Model Steel Structures Retrofitted with GFRP Composites under Microtremor Vibration

International Journal of Trend in Scientific Research and Development (IJTSRD)
Volume: 3 | Issue: 2 | Jan-Feb 2019 Available Online: www.ijtsrd.com e-ISSN: 2456 - 6470
@ IJTSRD | Unique Reference Paper ID – IJTSRD21455 | Volume – 3 | Issue – 2 | Jan-Feb 2019 Page: 729
Dynamic Analysis of Model Steel Structures Retrofitted with
GFRP Composites under Microtremor Vibration
Sertaç Tuhta, Furkan Günday, Hakan Aydın
Department of Civil Engineering, Ondokuz Mayis University,
Faculty of Engineering Atakum, Samsun, Turkey
ABSTRACT
There are many varieties of the structural and architectural structures strengthened with differentFRP composites aregaining
popularity, and there is a growing need to understand and compare the behavior of these structures before-after GFRP
composite strengthening. In this study,modelsteelstructurewastested on thebench-scaleearthquakesimulator (TheQuanser
Shake Table) using ambient vibration, to determine the dynamic response. After this, slabs of the model steel structure was
strengthened with GFRP composite, and tested on the bench-scale earthquake simulator (The Quanser Shake Table) using
ambient vibration, to determine the dynamic behavior. Finally, dynamic responses of model steel structure before and after
GFRP composite strengthening, such as displacements andmaximum-minimumacceleration, were compared.At theend of the
study, it is seen that displacements had decreased along the height of the model steel structure. Also, it is seen from the
earthquake analyses that GFRP strengthening is very effective on the dynamic responses of the model steel structure.
Keywords: Dynamic Analysis; GFRP; Microtremor Vibration; Shake Table
INTRODUCTION
Most of structures located in regions prone to earthquake
hazards suffer from various types of destruction caused by
seismic loads. Under such earthquake occurring, the parts
(especially the columns) of building structures suffer
damage. Looking on the other side, especially considering
the performance of such buildings under seismic
occurrence, there is a great need to strengthen the columns
even without changing their building masses; this clearly
shows that there is a need to investigate the connection
between technical repairing or strengthening procedures
and the column capacity. In this understanding, more
researches are being conducted to get required
performance of structures under seismic loading, by
means of looking at different point of view and directions.
In the literature, there are so many studies relation with the
behavior of structures or structural frame elements before
and after FRP composite retrofitting. Carbon fiber
composites and high performance fiber reinforced
composites (AFRP, BFRP, HMCF, etc.) utilized for the last
30 years by the aircraft, space and many industries, may
be employed to strengthen existing structures for civil
engineering purposes. Recently, application of fiber
reinforced plastic composite system by gluing them to
external part of the reinforced concrete structures is
gradually becoming popular for the aim of repairing and
strengthening (Yang et al. 2017), Keykha (2017), (Smyrou
et al. 2015), Elwan and Omar (2014). Fibers to be used, as
they have required characteristics include: glass, aramid and
carbon. The production of these fibers is done in two ways:
either as plates (covered by thin fibers) or as tissues
(knitted in one and two directions). The behavior of the
system that is covered with external FRP composite is
related to the type of the element covered. Generally FRPs
have been separated into three categories: bending
strengthening, shear strengthening and envelope scripts. In
order to strengthen reinforced concrete structures, the
prevention of severe bending and shearing is realized by
covering beams by FRP composite. Increasing the resistance
and ductility of the system under lateral seismic loads the
main goal of this covering. Li and Sung in (2003) they had
presented lot of analytical and experimental tests on
benchmark and on reinforced concrete damaged circular
bridge column. In the benchmark column is a 40% scale
reinforced concrete circular bridge column damaged
because of shear failure during a cyclic- loading test. Then
the column repaired by epoxy and non- shrinkage mortar
and rehabilitated by (GFRP) carbon fiber reinforced plastic
after the cyclic-loading test. Experimental result could be
predicted accurately by the analytical lateral force-
displacement relationship of the bridge columns, especially
in the nonlinear regions. In their study, for circular
reinforced concrete bridge column, the result has been
reached so that for a true repair; a change of the shear-
failure mode of bridge column to the bending-failure
refraction occurs, in other words this increases the seismic
performance the analyticaland experimentalby(Montoya et
al. 2004) are fitted with the numerical results of nonlinear
finite element evaluation for the behavior of steel and FRP
contained concrete columns which formulated and
implemented. The performance of reinforced concrete
column which was covered with carbon FRP was
determined under uniaxial compression load Cole (2001).
When Strengthened with CF-130 carbon fiber laminates,
the experimental result for five circular columns and
three rectangular columns were tested in pure compression
shows that ±45 degrees GFRP laminate can effectively be
used to provide columns ductility performance. When the
main goal is to boost the load capacity, a unidirectional
FRP laminate might be more effective according to Paretti
and Nanni (2002). According to Parvin and Wang study
(2002), they talk over the effect of strain gradient and
FRP thickness on square concrete columns reinforced
with FRP wraps. The results for nine square concrete
columns were tested under eccentric load and two different
levels of eccentricity. It was shown that the chosen
eccentricity values were small enough to produce any
longitudinal tension in the wrap. The aim of this study is

International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
to evaluate the performance of reinforced concrete
column, which has rectangular cross-section, under axial
static compression load by using analytical, numerical and
experimental evaluations and also to increase the source
of statistics with a comparison target on this field. It has
been shown that beams of existing structures suffer too
much during seismic loading. Reinforced concrete
rectangular cross-section column was used to evaluate
their performance under axial static compression load by
using analytical, numerical and experimental evaluations
and also to increase the source of statistics with a
comparison target on this field. It has been shown that
beams of existing structures suffer too much during seismic
loading.
analytical and experimental results by testing “T” cross
section reinforced concrete beam, the beams strengthen
with carbon fiber reinforced plastic composite (GFRP), the
results show that tension increased at the negative
moment region approximately 40% according to
(Namboorimadathil et al. 2002) study. The distance from
support to GFRP origin and effect of cross-section beam and
its behavior have been studied in (Ahmed et al. 2001) study,
when it was strengthened with GFRP composite at the
tensile region of reinforced concrete beam. Computation
formula has been composed related to experimental
results, to guess the design load that is equal to the limit
position of beam. In this examination original shear stress
and slight effect have been taken into consideration. The
performance of partial bridge strengthened by GFRP
composite has been tested in (Ramos et al. 2004) study. On
partial scaled and full-scaled specimen, partial beams
experiments were conducted. Bond scaled experiment has
been shown as alternative for characterizing repair and
strengthening the partial structures with GFRP composite.
For pre-stressed three reinforced concrete girder bridge
that suffered damage which repair-strengthening with GFRP
composite. Experimental results before and after repairing
was presented by (Klaiber et al. 2003) study, the results
shown that using of GFRP is productive. The girder
bending displacements have been decreased more than
20% when GFRP was used. When Strengthened with CF-130
carbon fiber laminates, fifteen rectangular beams were
tested in pure compression. The experimental result shows
that GFRP laminate can effectively be used to provide
beams ductility performance. The effect of FRP wrapping
number to the maximum axial capacity has been evaluated
Kasimzade and Tuhta (2012).
The Quanser Shake Table is a bench-scale earthquake
simulator ideal for teaching structural dynamics, control
topics related to earthquake, aerospace and mechanical
engineering and it is widely used in applications. In this
study investigated is the possibility of using the recorded
micro tremor data on ground level as ambient vibration
input excitation data for investigation, and the application
of Operational Modal Analysis (OMA) on the bench-scale
earthquake simulator (The Quanser Shake Table) for model
steel structure.
For this purpose, experimental modal analysis of a model
steel structure for dynamic characteristics was evaluated.
Then, retrofitted model steel structure for dynamic
characteristics was also evaluated. Ambient excitation was
provided by shake table from the recorded micro tremor
ambient vibration data on ground level. The Enhanced
Frequency Domain Decomposition is used for the output-
only modal identification. Model steel structure was tested
on the bench-scale earthquake simulator (The Quanser
Shake Table) using ambient vibration, to determine the
dynamic behavior. After this, slabs of the model steel
structure was strengthened with FRP composite, and tested
on the bench-scale earthquake simulator (The Quanser
Shake Table) using ambient vibration, to determine the
dynamic behavior.
Description of model steel structure
The Quanser shake table II is a uniaxial bench-scale shake
table. This unit can be controlled by appropriate software
illustrated in Figs. 1a, b, c. It is effective for various types of
experiments in civil engineering structures and models.
The specifications for the Shake table are shown below
Quanser (2008):
TABLE 1 SHAKE TABLE SPECIFICATIONS
Dimensions (H x L x W) (61 x 46 x 13) cm
Total mass 27.2 kg
Payload area (L x W) (46 x 46) cm
Maximum payload at 2.5 g 7.5 kg
Maximum travel ± 7.6 cm
Operational bandwidth 10 Hz
Maximum velocity 66.5 cm/s
Maximum acceleration 2.5 g
Lead screw pitch 1.27 cm/rev
Servomotor power 400 W
Amplifier maximum continuous
current
12.5 A
Motor maximum torque 7.82 N.m
Lead screw encoder resolution 8192 counts/rev
Effective stage position resolution 1.55 μm/count
Accelerometer range ± 49 m/s²
Accelerometer sensitivity 1.0 g/V
(a)
(b)

(c)
Figure 1a, b, c Illustration of model steel structure and
shake table
In modeling of beams and columns the modulus of
elasticity E=2.000E11 N/m2, Poisson ratio μ=0.3, mass per
unit volume ρ=78500 N/m3. Model steel structureis 1.03 m
height. Thickness of elements is 0.001588 m. The structure
dimensions are shown in Figure 1.
Shake table test of model steel structure
Real time history of model steel structure before and after
FRP composite strengthening were performed by using
acceleration values of ambient vibration. Record length is
100 minutes.
Figure 2 Ambient excitation data from the recorded
micro tremor data on ground level used in the shake
table
The excitation is provided by using ambient vibration on
shake table. Two accelerometers A and B (with both x and y
directional measures) are used to measure vibrations, one
of them is allocated as first floor, and other second floor
(shown by the red in Figure 3).
Figure 3 Accelerometers location of experimental
model in the 3D view
The absolute displacements and accelerations model steel
structure at the time of response before and after FRP
composite strengthening aregiven in table 2-3 and Figure4-
6.
TABLE 2 DISPLACEMENTS AND ACCELERATIONS OF
EXISTING MODEL STEEL STRUCTURE
Joint Acceleration
2
Displacement
(m)A 0.09360 0.0003490
B 0.12510 0.0006343
Figure 4a Node (A) Displacement and acceleration
graphics

Figure 4b Node (B) Displacement and acceleration
graphics
Shake table test of retrofitted model steel structure
In the case of retrofitted beams, the following are studies
made on it to check and examine the efficiency of using
unidirectional GFRP composite: beams of the model steel
structure are retrofitted with onelayerGFRP composite. The
Unidirectional GFRP composite and its components YKS
Fiber is product of YKS Corporation (Figure 5). The
properties of the dry carbon fiber composite are: E=4E10
N/m2, Poisson ratio μ=0.25, mass per unit volume ρ=18639
N/m3, thickness=0.000152 m.
Figure 5 GFRP composite and using details
The steps to pass through during retrofitting are shown
below in details: a thin layer two sided tape is applied
(Figure 5) to the beams, approximately 1 hour of curing in
order to prepare a surface for application of GFRP
composite. Next step, bottomsurface of beams is covered
with GFRP composites. After thesesetups,ambient vibration
tests are followed by curing to obtain absolute
displacements and accelerations similar to previously used
properties in order to obtain comparative measurements
(Figure 5 and table 3).
TABLE 3 DISPLACEMENTS AND ACCELERATIONS OF
RETROFITTED MODEL STEEL STRUCTURE
Joint
Acceleration
(m/s2)
Displacement
(m)
A 0.10670 0.0001592
B 0.12890 0.0003077
Figure 6a Node (A) Displacement and acceleration
graphics
Figure 6b Node (B) Displacement and acceleration
graphics

It was clearly seen from Figure 5 that application of FRP to
the model steel structure reduces the absolute
displacement values along the height of the structure. In
another words, the maximum absolute displacement value,
0.0006343 m, before FRP application, decreased to
0.0003077 m after FRP application. The decrease in
maximum absolute displacements was approximately
51,49 % without so many additional mass to the structure.
It is clearly seen from Figures. 4 and 5 that FRP composite is
very effective.
It is clear that using GFRP composites seems to be very
effective for strengthening steel members along with
increasing stiffness; this research aims to determine how
GFRP composite implementation affects structural response
of model steel structure by changing of dynamic
characteristics.
Conclusions
In this research, the conducted were both experimental
analysis of existing model steel structure and GFRP
composite retrofitted model steel structure. Comparing the
result of study, the followings are noticed:
From the shake table test, displacements range between
0.0001592 and 0.0006343 m.
The displacement difference lies in the interval of 51,49%-
54,38% for Existing and retrofitted case and it provides the
increase of frame structure stiffness about 52,94 %;
The investigated results ensure and confirm the
possibility of using the recorded micro tremor data on
ground level as ambient vibration input excitation data for
investigation and application of dynamic response on the
bench-scale earthquake simulator (The Quanser Shake
Table) for retrofitted structures and shed light on the
development of related research.
The conclusion of the experiment strongly suggests that the
retrofitting should be very efficient to increase stiffness and
decrease displacement.
In this study, it is shown that shake table test may be
used to evaluate the displacement and acceleration of the
retrofitted structures.
References
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reinforced concrete columns subjected to uniaxial
compression”, MSc Dissertation, UniversityofMissouri,
Rolla, USA.
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behavior of eccentrically loaded RC slender columns
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Dynamic Analysis of Model Steel Structures Retrofitted with GFRP Composites under Microtremor Vibration

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Dynamic Analysis of Model Steel Structures Retrofitted with GFRP Composites under Microtremor Vibration