Bridges: Salzachbruecke Mittersill

Case study: SOFO System

Pre-tensioned concrete road-bridge
Breakage monitoring of faulty tendon-wires
Long-term monitoring

Project Description

Summary: Monitoring permanent deformations due to possible breakage of faulty tendon-wires

Clients: Amt der Salzburger Landesregierung

Place: Salzburg (Austria)

Period: 2001 - N/A

Installation: RISS GmbH, Guntramsdorf, Austria

Structure's short description: Double-lane road bridge, total width: 10 m, drive lanes 6,6 m, pedestrian-walks 1,5 m on each side. Total length: 31 m, free length 25,7 m, prestressed with 8 tendons injected in 500 mm diameter steel-tubes with B400 concrete. Load carrying capacity: 25tons plus 14tons normal traffic, or 500 kg/m? distributed load or 60 tons special transport or caterpillar drive.

Aim of monitoring: Since the bridge was built in 1963 the traffic frequency and loads have multiplied as this bridge is the main thorough fare over the river Salzach. It was found, that a certain steel charge, used to make the tension cables was defective and sensitive to fatigue fracture cracks. Therefore the bridge has to be monitored over and above the regularly prescribed inspections. As a first step a frequency analysis was carried out in the year 2000. In addition, the government decided in April 2001 to have a deformation monitoring system installed, to take measurements every 3 month for the next 18 month. 3 SOFO Standard Sensors, each 8 m active length were installed on each side of the bottom concrete plate, in July 2001. Depending on the measurements it may be decided to change the period and duration of the program. The major aim is, to detect permanent deformations caused possibly by cracking of the tension-wires and thereby enabling immediate decisions regarding the safety of the bridge.

Number of sensor: 6

Main Results: N/A

Bibliography:

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