Assessment of the Structural Behavior of a Historic Timber Truss Bridge Under Lateral Wind Loads According to EN 1991-1-4

This study numerically investigates the structural behavior of a historic timber truss bridge under lateral wind loads determined in accordance with Eurocode wind provisions. The main objective is to evaluate the influence of wind not only at the level of global displacements but also in terms of internal force distribution in the main load-bearing members and the deck-supporting substructure. For this purpose, a three-dimensional numerical model of the bridge was developed, and linear elastic analyses were performed under dead load, pedestrian load, and wind load combinations. Wind loads were calculated by considering the geometric characteristics of the bridge, terrain roughness, topographic conditions, and the aerodynamic properties of the truss system. The equivalent horizontal wind forces were then distributed to the nodes through an area-based approach reflecting the actual geometry of the structure. The results show that lateral wind loading has its most pronounced influence on the transverse displacement response of the bridge. More importantly, significant effects are observed at the member level. Wind loading causes shifts in critical internal force regions, disrupts the previously balanced load-sharing pattern, and leads to the concentration of several critical demands in the shielded truss. In particular, the response of verticals, chord members, and diagonals changes noticeably under wind action, while the deck-supporting substructure remains predominantly flexure-controlled, with more pronounced axial and secondary flexural effects. Overall, the study demonstrates that lateral wind loading is a key parameter in the structural assessment of historic timber truss bridges and should be carefully considered in conservation, restoration, and adaptive reuse processes.