Strengthening the Röslautal Bridge Using Innovative Techniques, Germany

The Röslautal Bridge is a pre-stressed concrete box girder bridge situated in Germany close to the Czech border. It routes the European highway E48 heading to Prague over the valley of the Röslau creek. The continuously increasing heavy trans-European traffic required an additional third lane on the bridge deck. Elevated traffic loads required strengthening of the bridge, but due to its important role traffic had to be maintained on one lane throughout the construction period. The stringent limits in time and the impact on traffic imposed by the road authorities were met by applying innovative techniques. The box girders are strengthened with external post-tensioning tendons deviated at additional diaphragms cast with self-compacting concrete. Additional flexural capacity for cantilever slabs is provided by arranging carbon fibre reinforced polymer (CFRP) strips bonded in slits which are cut in the top surface of the deck slab. Since the mechanical properties of cold-curing epoxy adhesives are dependent on temperature, the thermal effects during construction and service life had to be evaluated. This article summarises the thermo-mechanical behaviour of epoxies, the consequences on design, and the accompanying monitoring program set up to assess long-time performance and strengthening efficiency. The Röslautal Bridge demonstrates that the use of innovative techniques generates aesthetical, logistical and economical advantages but requires a deep understanding of the applied methods.