Siggenthal

Emplacement

Siggenthal , Aargau Canton
Switzerland
See map: Google Maps

Arch bridge
Curvature and deformation monitoring
Scaffolding removal
Temperature-induced deformations

Système: 
System SOFO
Domaine: 
Domain Bridges
Clients: 
Aarau Canton
Début des travaux: 
2000
Fin des travaux: 
0
Installation: 
Geotechnisches Institut AG
Courte description: 
The Siggenthal bridge is a concrete arch bridge with an arch span of 117 m, being built over the Limmat River in Baden, Switzerland. The bridge also included two approaches with one span on one side and three spans on the other. The total length of the bridge is of 217 m. The arch has a variable width from 10 m at the ends, where it doubles in two parallel and distinct arc segments, and 8 m at the top. Its thickness is 0.8 m at the top and 1.4 m at the feet. The arch curve is made of 7 segments with inflexion points under the columns supporting the deck and slightly curved in-between. The deck is a longitudinally- and transversally-prestressed box girder with constant height. On the arch it is supported by two pair of columns on each side. In the central section, the arch and the deck fuse into a single structure. The arch construction proceeded in five successive concrete pouring phases, executed symmetrically and starting from the feet. After lowering of the scaffolding the arch was left free to stand unsupported. During the construction of the vertical columns and of the deck, the arch is stabilized by two temporary towers under the first columns.
Objectifs de contrôle: 
The aims of the installed monitoring system were: Monitoring of the local concrete deformations; Measurement of local curvatures in the vertical plane; Reconstruction of the perpendicular displacements of the whole arch. These measurements were to be carried out during the whole life span to the bridge, but with particular interest during the following phases: concreting of the different arch sections, removal of the scaffolding, free standing phase of the arch, installation of the temporary towers, construction of the supporting columns and of the deck, bridge testing, long-term, in-service monitoring. In order to allow the mentioned measurements, it was decided to install pairs of long-gage fiber optic sensors in the arch. Each pair is constituted by a sensor placed near to bottom of the arch thickness and one near the top. The two sensors are parallel to each other and to the arch axis. The instruments are installed near one of the abutments. The local concrete deformations are directly observable from the sensors readings. The curvature measurements are obtained by looking at the difference between the parallel sensors. Finally the perpendicular displacements are calculated by an appropriate algorithm based on the double-integration of the measured curvatures and taking the boundary conditions into account.
Nombre de capteurs: 
74
Résultats: 
It was possible to measure the local deformations of concrete and reconstruct the radial displacements during scaffolding removal and during the freestanding period of the arch. It was found that during summer the daily temperature influence on the arch is particularly large and should be taken into account when performing point-measurements like triangulation. The automatic and permanent monitoring system can follow the deformations during many days and provide a more reliable assessment of the “real” deformation of such a bridge.
Superstructure siggenthal
Temporary Central Measurement Point
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