According to Eurocode HRN EN 1991-2 and Croatian National Annex HRN EN 1991-2/NA highway and expressway bridges need to be designed for Load Model 1 (heavy vehicles) and Load Model 3 (special vehicles) traffic loads. Classes of special vehicles are defined in Annex A of HRN EN 1991-2, while the Croatian National Annex requires the use of 15 axle special vehicle with total weight of 3000 kN and axle loads of 200 kN. The simultaneity of LM1 and LM2 is also covered by the standard, depending on the travel speed of the special vehicles. Design practice has shown that these design requirements have notable impact on bridges in the 30 to 100 m span range. In this paper, the results of a parametric study on a group of continuous girder bridges with different spans and carriageway widths are presented, to determine the exact difference in resulting hogging and sagging moments and shear forces between LM1 and LM3 Load Models. Thus, the governing Load Model and its effect on the design for the relevant range of bridges is determined. A recommendation is made as to when each Load Model should be used in design.

bridges, eurocode, traffic loads, special vehicles, national annex, design