Historical Beam Bridge Model Identification after Changing its Structural System into an Arch

Historical steel beam bridge over Gliwice Canal located in a small city close to the eclectic palace from 19th century has been strengthened by suspension to new steel arches. The old structure was insufficient for fulfilling current demands of road traffic and clearance. Another issue was its localization in the vicinity of the palace and the lake, which are attractive recreational areas. Therefore, the new structure should be also ready for safe pedestrian and bicycle traffic.To fulfil those conditions and also to create a landmark bridge in this interesting spot, an arch structure was chosen. Designer decided to use the old bridge and its abutments as a part of the new structure. The deck was renovated and suspended to two inclined hingeless steel arches. To accommodate pedestrian and bicycle traffic, two external footbridges were also suspended to the same arches on both sides. Static and dynamic load tests of the bridge were conducted. An Operational Modal Analysis method was used to identify the dynamic model of the bridge. Due to a limited number of transducers and the simple procedure of the test, the compromise between effort and quality was established. Good correlation between assumptions from the design stage and the response of the erected bridge was confirmed.