During earthquakes, structures can be subject to many cycles of high strain. This can lead to cracking and a serious reduction in strength in comparison with the usual assumption of maintained strength during ductile cycling. This study reviews various methods for the prediction of cracking and compares them with results available in the literature. Crack prediction can be performed using one of the three basic methodologies: stress-life theory, strain-life theory, and the crack growth approach. These techniques are developed to determine the number of cycles to failure. Stress life theory is suitable when elastic stresses and strains are considered. However, for the components having nominal cyclic elastic stresses but local plastic deformation, local strain-life theory is used for predicting the fatigue life. In this work, the behaviour of a fully welded steel connection subjected to cyclic displacement loading, is analysed using the strain-life theories. Based on the results, it can be concluded that: FE modelling, in conjunction with strain life equations can approximately estimate the cycles to failure at the observed crack location on a beam framing into the connection. However the more highly stressed area in the connections "panel zone" did not crack in the experiments, perhaps because of the more complex stress field and defect orientation to the tensile stresses in this location. The connection was improved by adding triangular bracing gussets, in the plane of the beam and column webs. The FE model showed that stress and strain were decreased and the high strains moved from the panel zone to the gussets.
|Date of Award||1 Oct 2012|
- University Of Strathclyde
|Supervisor||Nigel Barltrop (Supervisor)|