Field measurements at a composite bridge with composite dowels as shear connectors - Economical Bridge Solutions based on Innovative Composite Dowels and Integrated Abutments - page 63

2. Monitoring concept

Due to symmetric reasons, all measurement devices were applied at the VFT-Rail ® girder
between axis 20 and axis 30 of the bridge structure only (“Fig. 2”). For measurement of the
strains in the composite dowel (“Fig. 1”, right), strain gauges were applied and connected
by wire during prefabrication of the elements in the workshop (section 4). Forces acting on
the rail support points N° 1 and N° 4 were measured by means of two conventional ECF
rail support points, equipped with special measurement devices (section 3). Furthermore
relative settlement and lowering of the first B90 railway sleeper in front of the bridge was
measured by means of two inductive displacement transducers. The temperature distribution
over the cross section was recorded permanently by three internal temperature gauges. These
measurements were completed by deformation measurements of the superstructure.
Continuous measurements (C) were performed in combination with temporary
measurements (T) to allow for a low-frequency recording of long term effects as well as
a high-frequency recording of short term loading due to single train crossings. Temporary
measurements were performed four times during a period of two years (summer and winter
measurements to cover a large temperature spectrum). In Tab. 1 the measurements are sum-
marized.

Table 1: Overview monitoring concept (type of measurement, type of data, N° of de-
vices, sampling rate)

type data N° of devices sampling rate

strain in steel component T relative 72 1000 Hz

forces on rail support points T / C absolute 14 1000 Hz / -

settlement of railway sleeper T / C absolute 2 1000 Hz / -

vertical deformation of
superstructure

T relative 1 1000 Hz

temperature C absolute 3 -

For static measurements a train of known weight was used (diesel electric locomotive
BR 132 “Ludmilla”, load per axle = 204 kN, “Fig. 5”). In total three „stop-runs“ were per-
formed, whereas the locomotive came to a stop every 2 meters on the VFT-Rail ® girder for
at least one minute.

Figure 5: Test train, class BR 132, Co'Co'

For dynamic measurements the same test train was used, whereas data was recorded
during 12 train crossings at speeds of 20, 60, 80 and 100 km/h. These measurements allow for
a quantification of the dynamic behavior of the structure [6] [7] [8]. Additional measurements
were performed during train crossings of scheduled passenger trains (“RegionalExpress”),
consisting of two class DBAG 612 railcars (“Fig. 6”).