Traffic Loading on Statically Indeterminate Bridges

Dutch national highway bridges have to cope with increasing traffic loads, causing steel bridges built in the 1970’s to suffer from fatigue problems. As a consequence there were assessments needed throughout the last decade to ensure safety. The resistance (strength) is relatively well understood compared to the loads that a bridge is subjected to. The use of the Eurocode is obligatory for the design, with additional national norms providing load reduction factors for existing structures. This results in costly refurbishments or even replacements, due to the fact that codes of practice are defined conservatively in order to be valid for a wide range of bridge types and loading conditions. The general load model is being reviewed here. An statistical analysis of highway bridge traffic loading is performed to determine if loads from the norm are realistic. Generally the objective is to assess the positive effect of influence lines/surfaces based on their shapes. This work focuses on longitudinal direction for theoretical single lane continuous spans of varying lengths over four supports, as well as existing bridges with multiple lanes and/or carriageways. Dynamic effects and interaction between vehicles and the structure are not considered. In this thesis 29 heavy vehicle types, with a unique statistical distribution established on WIM measurements are combined with a traffic micro-simulation model to obtain governing vehicle patterns. An extreme value analysis uses the results of dynamic simulations based on ten and one-year analysis to determine load effects during the lifetime of a bridge. The modified upper bound Gumbel distribution uses the monthly maximum load effects for extrapolation to the required exceedence probability. This method is applied to different span configurations. The study proves that the current standards are too conservative regarding influence line sensitive load effects. Factors that influence the load reduction were determined. The theoretical findings are complemented by assessments of existing bridges. Analysis of the transverse direction adds another dimension, increasing the load dependency on the influence lines. Although the findings are dependent on the structure and load effects, this study shows that load reduction based on the influence line shape is possible for crucial positions on a bridge. Theoretically this could lead to more economical bridge renovations.Concrete StructuresStructural EngineeringCivil Engineering and Geoscience