In response to a growing number of deteriorated and obsolete highway bridge decks, the Reynolds Metals Company has developed a multi-voided aluminum bridge deck system. The Virginia Department of Transportation (VDOT) agreed to implement the new aluminum deck system in a demonstration project. The Reynolds deck was employed to rehabilitate a functionally obsolete Route 58 highway bridge that spanned the Little Buffalo Creek near Clarksville, Virginia. Because the VDOT considered the project as experimental, the Virginia Transportation Research Council (VTRC) implemented a study to evaluate the structural performance and serviceability of the Reynolds system. This study involved both experimental and analytical evaluations of the rehabilitated Route 58 bridge. The VTRC performed two field tests to evaluate the bridge response. Instrumentation, consisting of various gages and transducers, measured deck and girder displacements, strains, and accelerations during controlled static and dynamic vehicular load tests. Analytical evaluations were performed with the commercial, general-purpose finite element code ABAQUS. Three-dimensional finite element models were developed to predict the overall structural response of the Route 58 bridge. Model accuracy was verified by using response data acquired from field testing. Girder displacements, uniaxial deck strains, longitudinal normal girder strains, and natural frequencies of vibration were predicted with reasonable accuracy. The validated finite element models of the structure were utilized to perform evaluations of the aluminum deck and steel girder response, composite action, natural frequencies of vibration, and mode shapes. Results from this study clearly demonstrate that aluminum bridge decks are a feasible alternative to reinforced concrete decks from the standpoint of strength and serviceability.

Experimental and analytical evaluation of an aluminum deck bridge

The easiest purchasing policy to enforce is least first cost. Under TQM (total quality management), the new mandate is to obtain least life cycle cost. Experience with highway bridge construction in the United States is that the usable life of the bridge deck is only one half of the useful life of the bridge. The average age of bridges when replaced is 68 years, and the average length of service of bridge decks before replacement is 35 years. Bridge deck replacement during the service life of the bridge is much more costly than a new deck on a new bridge, due primarily to the requirements of traffic maintenance during the construction phase of bridge rehabilitation projects. Estimation of the cost of construction of design options for life cycle and serviceability, although extremely difficult to document objectively, must now be accomplished. New public policy has enunciated the importance of determining relative life cycle costs. Estimated bridge costs in the 1950s were $20 to $40 per square foot. Estimates of bridge rehabilitation cost in the 1990s will be $70 to $200 per square foot. This paper reviews various bridge deck construction methods and the theoretical and historical comparisons which may be observed. A discussion of how design, construction, and service considerations impact life cycle cost and serviceabilty is included for several types of bridge deck. In his conclusions and recommendations, the author proposes guidelines for comparing available bridge deck types. The discussion includes checklists of specific project needs, whether new or rehabilitation designs, to meet the objective of matching bridge and deck useful life.

N H Bettigole

Papers

Designing bridge decks to match bridge life expectancy. extending the life of bridges--symposium, lake buena vista, florida, december 5, 1989