Description
In order to create a convenient pedestrian and bicycle crossing along the existing road bridge, the city authorities decided to adapt the existing heat pipeline supporting structure, located next to the road bridge, for this purpose. The three-span supporting structure with a total length of 109 m was built in 1975 from two steel plate girders, braced with crossbeams, on which a heat pipeline with a diameter of 100 cm was placed. In order to adapt the existing steel structure to the new live loads, the steel girders were strengthened by increasing their cross-section (bottom flange) and depth. Moreover, to minimize the dead load of the structure after the reconstruction, the lightweight FRP composite panels were used as a deck slab for the footbridge. The panels were connected to the steel girders by means of special connectors, but without the composite action between the steel girders and the deck slab. Due to the use of new material for the deck slab, the city administration required the implementation of a system for monitoring the technical condition of the panels. Therefore the monitoring system based on distributed fibre optic sensing (DFOS) technology has been implemented into the FRP panels. DFOS enables continuous measurements to be acquired along the entire length of the structure, which is particularly crucial for these types of bridge decks. Before the new footbridge was put into use, a proof load test of the superstructure was carried out to verify its load-bearing capacity and to check the operation of the monitoring system. The paper presents the method of strengthening of the steel structure, its final reconstruction method, the monitoring system of FRP panels, as well as the results of the proof load test and controlling of the monitoring system.
