Pont de la Poya Testbed

 

 

Pont de la Poya is bridge a large suspension bridge that was built between 2009 and 2013 to bypass the historic city of Fribourg (Switzerland) for road traffic. The overall length of the bypass is approximately 1.5 km, where 300m are in tunnel section and 850m are the suspension bridge. The bridge structure stretches across the river Saane at an average height of 70 metres above the valley floor. It bases on 10 pillars and 2 pylons reaching a height of 110 metres at maximum. The main distance between the pylons is 196 metres.

Historic town of Fribourg with the construction site of the Pont de la Poya in the background

 

The canton of Fribourg, as well as designers, planner and contractors of the Pont de la Poya construction site, kindly gave the permission and supported the installation of the prototype sensor network.

The GENESI network was installed at the Pont de la Poya in 2012 and 2013. Following measurements are taken:

  • Strains in auxiliary stiff bars for the tunnel construction (excavation pit)
  • Inclination of Pylons and pillars
  • Bearing displacements (mainly due to temperature)
  • Environmental parameters: Temperature, wind, Air pressure, Water levels, and soil moisture
  • It is planned to extent the network by accelerometers on the linking part of the bridge

The GENESI SHM, already starting during construction, and later also during the operation of the bridge has the following purpose:

Element Measurements Purpose during construction Purpose in operation
Stiff bars (in tunnel section) Strains (VW-strain gages) Detecting critical load states Stiff bars are removed in final construction – no sensing
Pylons Inclinations Detect critical situation due to construction (unsymmetric loading) and design faults Detect irregular behaviour during operation, possibly caused by/after impacts (storm, earthquakes and traffic accidents) Detect deformation / bending due to aging (strain in tension ropes)
Pillars Inclinations Detect critical situation due to construction and design faults Detect irregular behaviour during operation, possibly caused by/after impacts (natural and traffic accidents) Detect deformation / bending due to aging (e.g. strain in tension ropes or relocation of loads du to settlements)
Bearings deformations Not installed Check design values and detect irregular behaviour (e.g. due corrosion and settlements)
Bridge section/ Carriageway acceleration Not installed Detect impacts and irregular behaviour in oscillations
All section Environmental parameters: Temperature Wind Pressures etc. Detect environmental influence on bridge and on sensing elements Detect environmental influence on bridge and on sensing elements

 

The big advantage of the GENESI system in the Poya deployment was that the system could be installed stepwise node by node without significant extra effort, according to the progress of the construction works. Furthermore there are no cables which take long installation time, interfere with construction work and are likely to be damaged. After construction works are finished most of the sensors and nodes will stay in service. The gateway of the network will be simply moved from temporary containers to a service building.


With low power mode and energy harvesting the maintenance tasks for the SHM will be very low. When extraordinary events are happening or after irregular measurements, measurement intervals of nodes and sensor can easily be changed remotely.


Project partners have always access to real time data via a Solexperts WebDavis Webpage.

Bridge construction. GENESI system is extend over the complete structureGENESI node with inclination sensor and solar panelInstallation of node on pillarWebVisualization and Online-Graph with Solexperts WebDavis

 


 

 

Structural health monitoring
at Pont de la Poya White Paper