Vibration-based stress state identification method for iron and steel truss structures

Vibration-based stress state identification method for iron and steel truss structures The assessment of the load-bearing capacity of existing iron and steel truss structures is significantly dependent on the determination of the axial forces and corresponding stresses in axially loaded structural members. The axial forces in truss structures can be estimated by static calculations if accurate information about the structure and external loads are known. However, the stress condition for historical constructions can usually only be estimated inaccurately due to uncertainty in the assumptions of a static model. As an alternative to static calculations, non-destructive measurement based techniques can be used. The newly developed methodology is based on vibration measurements and the finite element model updating. The member forces of the truss members can be calculated by means of an analytically based algorithm and a comparison between the numerically computed and experimentally identified natural frequencies and mode shapes of the truss structure as well as of selected individual members. For the tested structural systems, the identified axial forces by the proposed methodology agree well with the experimentally measured axial forces at different stress states. Furthermore, practical recommendations for the preparation of a measurement concept and development of design strategies for in-situ investigations and safety assessment of existing iron and steel truss structures are given.