132
X2
Category 2: Civil Structures
Introduction
The cyclist- and pedestrian bridge in the centre of Metz
crosses the river Seille in the contemporary Parc de la
Seille. The bridge is officially known as the passerelle
de Graoully. The name refers to the mythical animal that
is the symbol of Metz: the dragon.
The 64-metre-long bridge has a changing width from
8.7 m to 8.4 m and a changing height from 7.5 m to
6.8 m.The total weight of the bridge is 100 tonnes.
The bridge has several cross girders in the form of a
“U”. These cross girders are connected by crossing
rectangular diagonals. The net of diagonals is in
equilibrium with a box-formed top girder that is anchored
on 1 side of the bridge to limit the deformation of the
bridge. The bridge is placed in one piece in its final place.
Description of technical questions to be resolved
with Scia Engineer
ESA-Prima Win was used both for the dimensioning
of the bridge in the traffic situation and the erection
engineering of the bridge.
The complex 3D structure was modelled in
Scia Engineer with bars. The possibility of input of 2D
dxf files in Scia Engineer was a big advantage so as to
form the 3D structure in Scia Engineer exactly. Sufficient
points were created in the bars to form the curved cross
girders by linear bars.
From the engineering point of view this project has
several challenges.
First, there was the complex form of the bridge. The
possibility of user-friendly input by Scia Engineer was a
big advantage. The use of 2D dxf files made it possible
to compose the 3D structure in Scia Engineer in a rapid
manner.
Second, there was the dynamic analysis of the bridge.
Because of the light and slender character of the
bridge there was the need to calculate the eigenvalues
/ frequencies of the bridge in order to check if there
were risks of vibration under pedestrian load or wind
actions. The possibility of calculation of accelerations
due to passing pedestrians in Scia Engineer was a big
advantage.
Third, there was the second order calculation needed
for the check of the box-formed top girder based on
a stability calculation. The twisting form of the girder
(referring to the dragon) and the elastic support of the
cross girders gave a complex stability form that was
used as input for the second order calculation.
Fourth, the evaluation of deformations during the
construction phase. The bridge was lifted in one piece to
its final position. The choice of the position of the lifting
lugs was important in order to evaluate the deformation
of the bridge during positioning.
Description of how our experience with
Scia Engineer proved its completeness
• Dimensioning a complex 3D structure in
Scia Engineer by input of 2D dxf files.
• The possibility of using and combining the results of
Scia Engineer in a flexible way.
• Stability calculation and second order calculations
based on a complex stability form.
• Checking the dynamic behaviour of the structure by
calculating the eigenvalues and the accelerations of
the structure.
This project proves the great diversity of Scia Engineer
in checking the structure.
Modules used:
• Base
• 3D frame
• Dynamics
• Steel code check (EC)
• Stability
Software: Scia Engineer
Cyclist- and Pedestrian Bridge - Metz, France
