A Comparison of Maximum Responses of Three-Span Continuous Bridges Due to Thai Trucks with AASHTO Highway Live Loadings

Abstract

Thai truck weights rated by Highway Department are different from the highway live loadingsspecified by the American Association of State Highway and Transportation Officials (AASHTO) standardspecifications. For bridge design practice in Thailand, the engineers intentionally multiply AASHTO designlive loads by a mark-up factor. These mark-up factors are derived from simply supported beams with severalspan lengths. This article has studied the maximum responses of three-unequal-span continuous bridgeswith the total length ranging from 90-180 meters due to Thai truck loads and the AASHTO loads. This studyaims to calculate the maximum shear ratios and bending moment ratios of the continuous beam bridges.The results show that, in each type of bridge, the maximum shear and bending moment are mostly causedby the truck which has 45 tons total weight. From the structural analysis, the shear ratios and the momentratios, varying from 1.312-1.954, are computed associated with various bridge span lengths. Furthermore,the ratios in some type of continuous bridge are 27.76% greater than those found from the previous simplysupported beam bridges having the same span length. These ratios could be applied as multipliers to theAASHTO loads; therefore, the bridge responses are comparable to those of Thai truck loads.