Cable-Stayed Bridge Loads Caused by Traffic Congestion on the Deck Measured with Bridge Monitoring System

Structural safety of a bridge depends, among other things, on the number of vehicles passing on its deck, their weights and distribution of loads to their axes. A large number of vehicles can accumulate on the bridge in a controlled state, i.e., during an acceptance test including load testing, and during traffic congestion on the bridge, which is a fortuitous event addressed in this paper. The paper deals with the analysis of load intensity on one bridge carriageway when it is fully and randomly filled during traffic congestion. The influence functions of the forces in the cables are used to determine the effects of loads exerted by the vehicles moving at very low speed. Effects of such loads are studied considering an exemplary cable-stayed bridge. Since the measurement basis was limited, the iterative algorithm was used. It consists in shortening the girder sections under analysis to the area appropriate for determining the load in each successive step of iteration. Ineffectiveness of the traditional algorithm, where the determined system of equations is resolved, is an important premise for using such algorithm. The results of numerical analysis show that the load intensity caused by traffic congestion is relatively high. It has been demonstrated that the matrix method may be successfully used to determine the real load of bridges on the basis of selected parameters measured in the bridge structure, also for complex scheme bridges, including the cable-stayed bridges.