Fig: Tacoma Narrows Bridge
(July 1940 to oct,1940)
Fig: Missipi river bridge collapse in 2008
(nov,1967 to sep,2008)
Spectacular accidents have motivated the community to improve safety
Evolution of materials
Reference : American iron
and steel institute/U.S
department of energy
Reference : dallara altairamerica HTC , maya2012
The advantages of composite structures are that they
can be designed to suit the requirements of a specific
application or to enhance some properties of the
structure such as
Strength and stiffness in desired directions of
desired temperature-dependent behavior . etc
Composite materials are used in almost all aspects of
the industrial and commercial fields in aircraft, ships,
common vehicles, medical application , construction
Their most attractive properties are the high strength-
to-weight ratio and high stiffness-to weight ratio
These new materials also have some problems such as
fiber breakage, matrix cracking, debonding, and
This damage can cause degradation of strength and
overall stiffness for a laminate structure.
The presence of delamination can also significantly
reduce the buckling load and compressive strength of
the composite laminate
One of the main reason for the failure of the equipment
made by composite material is due to fatigue .
So S.H.M. is necessary to predicts the life and type of failure
in the specimen.
Structural vibration and acoustics
Electro mechanical impedance
Main difficulties to use this techniques are
frequency range and resolution is limited .
Capture signals from other environmental noise
while the structure is in operation.
Required completely damp zone.
Testing equipment need to be in contact with the
To overcome these drawbacks, vibration based
techniques for a structural health monitoring (SHM)
tool use to identify and assess defects.
The key purpose of SHM is to ensure rapid assessment
of the health condition of a structure in terms of
reliability and safety.
Advantage of vibration base technique
not having contact with the specimen.
ample frequency response.