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the tightening torque method whereas the final exact pre-stress was applied by means of the
calibration factor
ktension,1
, monitoring the strain in the bolts. The set of measurement bolts
used for this cyclic test was not re-used in the final bridge structure.
Figure 11:
Mean lowering / deformation of the ribbed base plate depending on the force
applied (20% pre-stress, 100% pre-stress)
The mean lowering of the ribbed base plate was measured by means of four displace-
ment transducers and plotted against the jack force (“Fig. 11”). In this way the vertical stiff-
ness of the rail support point structure under compression was determined. Within the elastic
region of the elastic intermediate layer this stiffness equals the stiffness determined by TU
Munich (research report N° 1689a, see chapter 3.1) as well as the stiffness used for design
(
kpressure
=22.5 kN/mm). However, due to the non-linear force-deformation behavior of the
elastomer for compression forces > 45 kN, the secant stiffness (
kpressure
=29kN/mm) at
F
=
70 kN was used within the scope of the monitoring, leading to slightly conservative values
for small deformations.
Figure 12:
Strain change in measurement bolt S2 depending on applied force (20% pre-
stressed, 100% pre-stressed)
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