Evaluation of Forces on a Steel Truss Structure Using Modified Resonance Frequency

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 structures. To check Structure conditions, a non-destructive testing such as resonance frequency testing, provides an alternative solution. Based on literature studies carried out on resonance frequency testing for the determination of axial forces, a simple truss structure was modelled. The truss structure has 2 members with equal steel section of L.30.30.3, each acting as 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 the 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 behaviour and closer to fixed rather than pinned conditions.