Bridges: Pont Canal

Case study: SOFO System

Channel bridge monitoring
Spatial deformation analysis
SPADS compared with water levels and FEM

Project Description

Summary: Spatial deformation monitoring of a complex structure of channel bridge, designed for internal havy loaded ships navigation. The SOFO sensors are embedded in prefabricated concrete elements and also cast-on-site in some sections of the bridge.

Clients: Federal Transport administration of Wallonie

Place: Houdeng (Belgium)

Period: 2000 - N/A

Installation: University of Li?e

Structure's short description: Located 50 km south of Brussels, the Sart Canal-Bridge belongs to modernisation works up-grading a 100 year old canal waterway to meet European Standards for modern barges. The deck, of 498m long, is made up of 13 continuous central spans of 36m and 2 cantilever end spans of 15m. The two walls are 7,10m high. The ratio between the height and the span, in this case about 1/5, is synonymous of a very high stiffness of the bridge. That's why the margin with regard to the theoretical levels is limited to 5mm. It's then essential to take particular care to place the bearings. Crosswise, the width between the bearings is of 33,40m and, at the top (at the towpaths level), is of 46m. The bottom of the deck is supported by concrete beams of 27m long and for which the height varies between 1,3m at the ends and 3m at the centre (fish belly form). Placed all 4,5m, these beams, of about 80 tons for one piece, are carried by night by wide load. The bridge counts a total of 111 beams. These ones are placed by means of two cranes which can take a charge of 40 tons with a jib of 20m. The bottom flag is 40cm thick for the span beams and 60cm for these which are placed straight above the columns. Incremental launching of 12 m per week of a 65 000 t deck was a world record.

Aim of monitoring: The main aim of the project has been to monitor 11 transverse beams and 2 walls in order to control the load transfer. Vertical displacement in the transverse beams was retrieved by the double integration algorithm and SPDS software. For this purpose, 140 SOFO sensors of 0,5 ; 1 and 4 meter active length and 20 thermocouples were placed in the transverse beam. 5 measurement curvature with 3 SOFO sensors fitted each beams and 6 longitudinal SOFO sensors were placed in the wall for one section.All sensors were installed before the pouring in a concrete prefabricated plant. All the sensors were connected on-site to a central measurement point.

Number of sensor: 88

Main Results: Local deformation of the transverse beam was measured with a good precision. For the load case "Filling of 2 meter of water in the canal", fiber optic optic sensor confirm the 3D finite element calculation and increase the knowledge of the bridge behaviour. Calculation of the vertical displacement from the SOFO sensor and SPADS algorithm were confirmed with optical levelling system and non linear FEM calculation.

Design and construction of the bridge

View to installed sensors and components

Comparison between SOFO SPADS calculus, FEM analysis and water-level measurements

Bibliography:

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