| Summary: | Structural decay may be defined as any deviation in a structure�s original
geometry or material properties that may cause undesirable stresses,
displacements, and vibrations in the structure. This decay may be due to cracks,
loose bolts, broken welds, corrosion, or fatigue. In addition, many bridges are
decayed due to aging, misuse, lack of repair, and, in some cases, caused by
improper design. Conventional inspection remains the most commonly used
method for the structural evaluation of bridges. Conventional inspection can be
costly and time consuming, especially when disassembly is necessary to provide
access to the area being inspected. Nondestructive testing such as resonance
frequency analysis provides an alternative solution.
Based on literature study carried out on resonance frequency testing for
the determination of axial forces, a simple truss structure was modeled. The truss
structure has 2 members using equal steel section of L.30.30.3, each acting as a
compression and tension members, and then applied load was accomplished by
hanging a steel block on the tip of the truss being tested. Finally, transversal
frequency measurements were performed on the truss members under various
load levels. The collected resonance frequencies were then evaluated using
Bernoulli beam theory to estimate member forces and rotational spring parameter
at the ends of the member.
This research shows that the error of estimation of member forces in compression
and tension members using modified natural frequency and rotational spring
parameter by linear regression method varies from 0.26% to 1.99% and 0.2% to
2.41% respectively. The value of rotational spring parameters indicates that the
members have semi rigid behavior and closer to fixed rather than pinned
conditions.
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