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123456789_123456789_1	123456789	Concrete Bridge Software Case study	ICDAS COB 2019.00R Road Bridge Model Examples
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05-03-2015

New Railway bridge over Kalbyrisvej 2016, Zealand Denmark

COWI Project A051870

Short bridges in concrete with high natural frequencies

This case study presents concrete railway bridge over Kalbyrisvej i Zealand Denmark, of span only 5.350m.

Extreme short bridges in concrete are too stiff that its natural vertical frequency exceeded the upper limit

of frequency range for free of dynamic analysis. This range is calculated by Eurocode 1 DS/EN 1991-2 for the

Kalbyrisvej bridge as [14.953-27.028Hz]

Lusas animations below show the natural mode shapes and frequencies of the bridge deck. The deck cross

section have been designed to obtain the 1st natural bending frequency of around 27Hz.

Figure 1: First design of continued inner edgebeams, f=29.163Hz. See in 4020 pixels

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Figure 2: Second design the inner edgebeams in 3 slices, f=27.206Hz. See in 4020 pixels

For both of models the following E-modulus and concrete density are used:

Long term E(t) ~ Ecm*0.70=34000*0.70=23800MPa

Density 2.5ton*1.85 incl. weight of ballast, rail and equiments (not shown)

In the design 2 the inner edgebeams are sliced in three slices to reduce the overall stiffness of bridge deck.
The 1st natural bending frequency is reduced to around 27Hz.

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123456789_123456789_1	123456789	ICDAS • Hans Erik Nielsens Vej 3 • DK-3650 Ølstykke • E-mail: th@icdas.dk • Tel.: +45 60 53 83 79 • CVR no.: 34436169