Modifying the dead load partial factor of the Nibelungen Bridge based on 3D measurements

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Bridges are commonly assessed using the partial factor method (PFM) according to Eurocode 0 in Germany. However, this method conceived for the design of new structures may lead to conservative results for existing bridges. To address this issue, fib Bulletin 80 proposes the design value method (DVM) and adjusted partial factor method (APFM) to recalibrate the partial factors for existing concrete structures based on in-situ measurements. This paper focuses on the application of DVM and APFM to adjust the dead load partial factor, using the pilot area of the Nibelungen Bridge in Worms as a case study. To achieve this, the uncertainties in the bridge’s geometry, concrete density, and reinforcement content must be determined. A comparison of 33 cross-sections between the as-designed and the as-is models reveals an average deviation of 2% in geometry. The variation of concrete density is estimated using empirical literature values taking into account the reinforcement content. Both methods yield similar results, suggesting that reducing the partial factor above 1.20 may be possible. Nevertheless, further investigations on the geometry of the whole river bridge, the concrete density, and the reinforcement content are necessary to justify a reduction of the dead load partial factor of the Nibelungen Bridge.