World Journal of EngineeringICCE-19 Shanghai, China, July 24-30, 2011
ANALYSIS OF SANDWICHED COMPOSITE LONG-SPAN
FOLDABLE BEAM
Norazman M. Nor, Agusril, Alias Yusof, Risby Sohaimi, & Ahmad M.A. Zaidi
Faculty of Engineering, Universiti Pertahanan Nasional Malaysia
Sungai Besi Camp, 57000 Kuala Lumpur, MALAYSIA
Oral presentation - Corresponding author (azman@upnm.edu.my)
Keywords: Composite Material, Foldable Beam, Sandwiched Composite, Finite Element Analysis
Introduction
Foldable beam is very important in the military for
various temporary structures. However, it becomes
more important nowadays for disaster relief
operations. In the early days, military bridges were
made from steel causing the weight of the bridge to
be huge, thus, need more vehicles to transport the
bridge and crane with higher capacity to erect it.
Subsequently it will cost more to operate. To
overcome these problems, aluminium and metal
alloy were introduced to reduce the weight of such
structure.
Then new material emerge called
composite material, i.e. Fiber Reinforced Polymer
(FRP) [1, 2, 3].
International nongovernment organizations (NGOs)
have an intense interest in cross-country mobility
where infrastructure may have been badly damaged
by various incidents, conflict or natural disaster [4,
5]. The foldable beam system can also be use for
various other needs such as to build shelter,
bunkers, and to cover damaged road surface.
CFRP (Carbon Fiber Reinforced Polymer) is being
considered to be used as primary material for the
foldable beam. The reason to use the CFRP as the
primary material is due to its high strength to
weight ratio, thus making it lighter than steel and
other alloy. In this research, a foldable beam is
designed using Finite Element Method, several
simulations are made to test several lay-up
including use of core to increase stiffness of the
member.
Fig. 1 Dimension of beam with 3 connected sections.
Finite Element Analysis of the Beam
In the analysis, the quadrilateral elements with four
nodes were used in meshing of the beam. The
Laminate Modeller Facility in MSC PATRAN[6]
was used to apply lamina composite material
properties.
For the purpose of this research, the loads were
applied at the top-flange of the beam. The load
applied as multiple line load and distributed load
for imposed and dead loads, respectively.
Study on the effect of lamina and core thickness
on the deflection of the beam
The thickness of laminate and core on each part of
the beam such as top, bottom flange and the web, at
the mid and ramp-sections was observed. The
purpose of this study is to investigate the effect of
adding core on the structure and to determine the
location of core in order to optimise the design.
The optimization in design will be achieved if we
can determine the minimum thickness of the
laminate and the core, as well as the placement of
the core that results in minimum stresses and
strains, and within acceptable deflection limit.
In general we know that adding laminate and core
thickness at any part will improve performance of
the bridge at the cost of the bridge become heavier.
Thus, in the simulation processes, we need to
optimise the design so that we can achieve the
required performance with lightest structure.
Preliminary Design
In preliminary design, dimensions of the beam is
defined, then simple analysis is performed using
finite element software to observe the response of
the beam subjected to the loads.
The initial dimensions of the bridge main beam
have total length upto 30 m, width of 1.5 m, and
height of 1 m as shown in Fig. 1.
877
World Journal of EngineeringICCE-19 Shanghai, China, July 24-30, 2011
Comparison between Static and Dynamic
Analyses
Table 1 shows that generally the responses for static
analyses are greater than dynamic analyses, except
for flexure stress y. However, the stress (y) are
still under the permitted strength of material and
thus having sufficient factor of safety. From the
results shown, we conclude that the Impact Factor
(IF) of 1.2 as required by TDTC [8] can cover the
dynamic effect caused by movements of vehicle on
the bridge.
means that the requirements in TDTC to include the
Impact Factor (IF) of 1.2 is sufficient to cover the
dynamic effect.
The performance of the bridge to resist the local
buckling effect was achieved by using the core
layer in the web. However, the deflection is found
to be most critical criteria for design of bridge beam
from CFRP. But this problem can be overcome by
arranging the fibre orientation dominant in 0o or
parallel to the length of the beam and using the core
to stiffen the structure.
Table 1 Comparative Structure Responses to Load.
[7]
Acknowledgement
The writers gratefully acknowledge Universiti
Pertahanan Nasional Malaysia (UPNM) and
Ministry of Science, Technology and Innovation
(MOSTI) Malaysia for the support and finance
provided to this research project.
Responses
Flex. Stress
x (MPa)
Flex. Stress
y (MPa)
Shear Stress
xy (MPa)
Value
Static
Location
-104
top-ramp
-4.48
top-ramp
-8.35
web-ramp
Dynamic
Value
Location
Bottom75.1
all
Bottom13.5
ramp
Bottom4.06
ramp
References
[1]
Performance analysis
The failure of structure was observed using failure
criterion such as maximum stress theory, maximum
strain theory, Tsai-Wu theory, and Tsai-Hill theory.
In this analysis as shown in Fig. 2, where the
stresses of structure still within the allowable range,
it means that the structure will not fail under the
designed load.
[2]
[3]
[4]
[5]
Fig. 2 Failure criterion graphics in MSI unit.[9]
[6]
[7]
Conclusion
From the literature, we realised that portable bridge
is very useful in time of emergency and in conflict
areas. General characteristic of portable bridges are:
light, easy in transporting, handling, launching and
retracting. The use of composite materials i.e.
CFRP for the bridge structure can fulfil such
requirements successfully.
Static and dynamic analyses have been performed
to investigate the effect of vehicle’s movement on
the bridge and the results from both analyses were
compared. As expected, the comparison shows that
the structure response to dynamic analysis was
lesser than the static analysis with impact factor. It
[8]
[9]
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