Hyland Consultants investigated the condition of hanger stay bolts of a large stadium roof subject to fatigue loads from wind.  The purpose was to determine what level of fatigue damage may have occurred in the 30 years since construction and to estimate what the remaining working lives of the hanger bolts were. 

Initial assessment of the structure involved development of a 3D computer model of the stadium roof and fatigue assessment using code based approaches.  Analyses were then undertaken using a wind loading spectra developed from local wind records and critical components were analysed using a fracture mechanics crack growth based method and in-house software.  Site inspections incorporating ultrasonic inspection of hanger bolts were then undertaken in critical areas.  To calibrate the analytical models selected hanger stays were monitored with strain gauges to characterise the response of the hangers to varying levels and directions of wind over a 4 month period.  The results were then used to update the analytical models and develop recommendations for maintenance.