Distribution of wheel loads on highway bridges

PROPOSED REVISIONS ARE PRESENTED TO THOSE SECTIONS OF THE AASHO SPECIFICATIONS FOR HIGHWAY BRIDGES HAVING TO DO WITH THE DISTRIBUTION OF WHEEL LOADS ON BRIDGE DECKS. THE STATIC DISTRIBUTION OF MOVABLE WHEEL LOADS WAS STUDIED IN A BROAD RANGE OF BRIDGE TYPES. HOWEVER, THE STUDY WAS LIMITED TO SHORT-AND MEDIUM-SPAN BRIDGES; BRIDGES WITH SPANS UP TO ABOUT 120 FEET. THE BRIDGE TYPES IN THIS SPAN RANGE CAN BE CLASSIFIED: BEAM AND SLAB, MULTI-BEAM, AND CAST-IN-PLACE CONCRETE BOX GIRDER. THE BEHAVIOR OF THESE BRIDGES CAN BE CHARACTERIZED BY THE FOLLOWING MAJOR VARIBLES: ASPECT RATIO (BRIDGE WIDTH/BRIDGE SPAN), RELATIVE STIFFNESS OF BEAMS AND FLOOR, RELATIVE DIAPHRAGM STIFFNESS, AND EXTENT OF BRIDGE CONTINUITY. FROM AN EXTENSIVE LITERATURE SEARCH AND A STUDY OF AVAILABLE METHODS OF ANALYSIS, IT WAS FOUND THAT THE DISTRIBUTION OF REAL LOADS IN THSES BRIDGE TYPES COULD BE DETERMINED USING THE FOLLOWING THEORIES: (1) ORTHOTROPIC PLATE THEORY, (2) ARTICULATED PLATE THEORY, AND (3) PRISMATIC FOLDED-PLATE THEORY. THE MAJOR VARIABLES WHICH AFFECT THE LOAD DISTRIBUTION IN EACH OF THE MAJOR BRIDGE TYPES ARE: RELATIVE FLEXURAL STIFFNESS IN LONGITUDINAL AND TRANSVERSE DIRECTIONS, RELATIVE TORSIONAL STIFFNESS IN THE SAME DIRECTIONS, BRIDGE WIDTH, AND EFFECTIVE BRIDGE SPAN. IT IS FELT THAT WITH THE NEW DESIGN CRITERIA PRESENTED, PREDICTION OF WHEEL LOAD DISTRIBUTION WILL BE MORE ACCURATE, AND WILL MORE TRULY INDICATE THE BEHAVIOR OF THE BRIDGE TYPES STUDIED.