Civil Engineering Reference
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The mean values of static forces recorded during a stop-run of the test train are plotted
over the position of the train on the bridge for rail support point 1 and 4 (“Fig. 14”). These
measured values correlate well with the characteristic calculated values (section 3.1). It can
therefore be concluded that the design model chosen can be considered as sufficient.
A comparison of these results with the values recorded during “dynamic” train cross-
ing at higher speeds shows that in the case of the present structure the velocity of the train
crossing the bridge does not influence the forces acting on the rail support points. A dynamic
amplification of forces could not be observed.
Figure 14:
Compression force / tension force acting on controlling rail support points 1
(left) and 4 (right), caused by static loading (test train)
4. Local stresses in external reinforcement
4.1
Determination of design values
The internal forces needed for the determination of stresses were determined by means of
a framework model. The section stiffness was calculated according to elasticity theory for
condition I (uncracked concrete, “Fig. 15”, left) as well as for condition II (cracked con-
crete in tension zone, “Fig. 15”, right). In the case of condition II, tension stiffening was
disregarded (cracked concrete not contributing to stiffness, Young's modulus of cracked
concrete set to E
c
=0). In the region of compression, concrete action was considered with
non-reduced Young's modulus. For the determination of the tension zone's height, neutral
axis z
i,total
= 38.4cm from condition I was considered without iteration. In both cases, next to
external reinforcement, internal reinforcement (32 x Ø32) was taken into consideration as
well. Especially in condition II, the influence of this so-called redundancy reinforcement on
the total stiffness of the cross section could not be disregarded.
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