Field measurements at a composite bridge with composite dowels as shear connectors - Economical Bridge Solutions based on Innovative Composite Dowels and Integrated Abutments - page 71

Figure 15: Cross section for condition I (left) and condition II (right), rail support point

drawn in for illustration purposes only

Internal bending moment M as well as internal shear force V were determined in the
monitored sections for different load positions of test train BR 132 (“Fig. 5”). Therefore the
loading of a single axle was applied step-wise to the framework model with a step-size of
1m, starting at axis 30 of the bridge. Based on these internal forces, normal stresses were
calculated at the inner side of the upper and lower flanges, at the web as well as at the steel
dowel (close to the stress hot-spot).
The stress calculation in the flanges as well as in the web was based on the global bend-
ing moment only. An amplification due to local stress concentration had not to be considered
in this region, the stress amplification factor f global was set to 1.0. The calculation of stresses in
the region of the steel dowel was based on the global bending moment as well as on internal
shear forces. There the stress amplification due to structural effects as well as local bending
of the steel dowel (caused by internal shear forces) was considered by means of the stress
amplification factors k f,G,CL and k f,L;CL . Conservatively the stresses of both hot-spots were
summed up [15] [16].

4.2 Field measurements

4.2.1 Test set-up and measurement

Due to symmetry of the VFT-Rail ® girder, the strain gauges were applied at the four left steel
girders (2 top-girders, 2 bottom-girders, “Fig. 17”) between axis 20 and axis 30 of the bridge
structure only.