A comparison of the in-service response of an orthotropic steel deck with laboratory studies and design assumptions

A comprehensive research program, which included both laboratory and field testing, and detailed finite element analysis has been conducted on a steel orthotropic bridge deck. The laboratory testing verified that if a combination groove/fillet weld is used to make the connection between the longitudinal ribs and the diaphragm plate, the fatigue resistance is consistent with AASHTO Category C. In-plane and out-of-plane stress components were calculated at locations where strain gages were placed back-to-back on the diaphragm plate. An evaluation of the measurements revealed that the in-plane component dominated the stress-range cycle.; A field testing program was conducted to investigate in-situ stress-ranges and to compare the field and laboratory behavior. The controlled load tests indicated that there was little dynamic amplification and the addition of the wearing surface has little influence on stresses adjacent to the cutout. The field tests also verified that the laboratory test accurately replicated the actual proportions of in-plane and out-of-plane stresses. It was also found that the passage of a single truck results in a single stress cycle at the cutout.; Long-term remote monitoring of the Williamsburg Bridge orthotropic deck diaphragm indicated that the variable amplitude stress-range spectrum has a wider band than assumed in the AASHTO LRFD Bridge Design Specifications. Measured stress-range histograms indicated the fatigue-limit-state truck (i.e., 2 x HS-15) assumed in the AASHTO Specifications might not be conservative for fatigue design of certain details of an orthotropic deck.; Based on this research, a methodology for the fatigue design of diaphragm and bulkhead plates was developed. It is anticipated that this method will be submitted for inclusion in the AASHTO Specifications. The design method also includes a proposed fatigue-limit-state load for orthotropic decks equal to 3 x HS-15.; Finite element parametric studies related to the cutout geometry revealed that the geometry shown in the current (2002) AASHTO Specifications results in higher stresses at the cutout than the more flexible or open type cutouts. As a result, recommendations to modify the current sketch in AASHTO are provided. The studies have also shown that bulkhead misalignment of only 1/16 inch increases the out-of-plane stress component.