LICENTIATE THESIS - Luleå tekniska universitet

Evaluation of Concrete Structures
The trough consists of a slab connected to and carried by two longitudinal beams. The
bridges of this standard type were usually built between 1950 and 1980 with a concrete
compression strength of about 40 MPa (tested on 150 mm cubes). The older bridges
were designed according to principles where the shear capacity of the concrete was
somewhat overestimated. This leads to problems when the bridges are recalculated with
the design strength for the higher axle loads.
The load case that has been used for the calculation is shown in Figure 5.1, Figure 5.2
and Figure 5.3.
~750 1700 1500 1700
- 24 -
~750
Figure 5.1 Load case with two bogies from two iron ore wagons, Nilsson et al.
(1999).
~1540
3100
Figure 5.2 Cross-section of the Lautajokki Bridge, Nilsson et al. (1999).
φ16 s100
B=1000
600
320
d=295
Figure 5.3 Reinforcement in the longitudinal direction in the slab in the
Lautajokki Bridge.
The comparison can also be found in the report Thun et al. (2000).
5.2 Results and Discussion
First of all it must be said once again that it is very difficult to make a comparison of
this kind between the codes. Though, this comparison nevertheless gives an idea how
the two codes are designed.
One general difference between the codes is how you check the fatigue capacity. In
Eurocode you have three different “levels”. The first check is very easy to perform
since the calculations are very basic. If your structure passes this level you do not have
to go any further. The following level needs more calculations and more information