Bridge Fatigue Assessment
Structural model validation to assess fatigue life of critical bridge components
The Interstate 91 Viaduct, constructed in the late 1960’s, is an elevated bridge running through Springfield, Massachusetts. The elevated structure consists of multiple simply supported spans with a length of approximately one mile and was in need of replacement. Based on the feasibility study performed by CME Associates, the Massachusetts Department of Transportation (DOT) opted to rebuild the viaduct by performing a full deck replacement and evaluate the existing structure through instrumentation and monitoring to provide a minimum 20 year service life.
Geocomp’s installed 150 spot weldable strain gages on superstructure steel members and collected data continuously for a two week period using a remote access high-speed data logging system. In order to process the data, Geocomp developed an automated program to perform the stress loading cycle counting for the fatigue analysis in accordance with ASTM E1049-85 – standard practices for cycle counting in fatigue analysis. The data collected allowed for a differentiation between traffic stress loading and thermal induced stresses, which often can be significantly greater than live load stresses.