Load carrying capacity of bridges: three case studies of bridges in northern Sweden where probabilistic methods have been used to study effects of monitoring and strengthening

Probabilistic methods are presented for the assessment of bridges. Load carrying capacity calculations and evaluations of strengthening methods are carried out for three road bridges in northern Sweden: 1) The E4-bridge over Pite River - A four span steel beam bridge with a concrete deck built in 1969. The capacity of the edge beams are evaluated with use of calculations and monitoring results. Strengthening measures are discussed and recommended. 2) Bridge over Kuivajärvi - A one span concrete slab-frame bridge built in 1954. The supports have moved transversally towards each other causing cracking in the deck. Strains and deflections are monitored and the capacity is evaluated. 3) Bridge over Åhedån - A one span concrete beam-frame bridge built in 1934. The bridge was to be widened and the load carrying capacity of an increased cross section is studied. Monitoring and testing of material properties have given valuable information of the real behaviour of the studied bridges. Bayesian updating of original data has been shown to be very useful. Further research work is needed regarding the uncertainty coefficients for the studied models and parameters in order to fully take advantage of the possibilities to assess existing bridges with probabilistic methods.