M6 Bescot and M5 Oldbury Viaducts (CS4)

Hidden defect: Internal box sections

Problem: Concerns were raised regarding the condition of welded box sections on the bridge structure and their susceptibility to fatigue damage.

Solution: JF Strainstall designed and installed unattended dynamic monitoring systems to measure the strain under live traffic loading over a one month period at each site. Each location was fitted with 150 gauges and the data collected was used to calculate the fatigue life consumption at both locations.

Trowse Bridge and Caerphilly Station

Hidden defect: Deck plates, jack arches

Problem: The degree of load transfer from the deck plates to longitudinal beams was unknown, causing assessment calculations to call for a weight limit to be imposed on the bridge.

Solution: JF Strainstall completed controlled static load testing. The use of known weights combined with the measurement of displacement and strain enabled more accurate assessments to take place at the site.

Forth Road Bridge

Hidden defect: Fatigue cracking

Problem: During a routine inspection, damage to the bridge was noted. This included the complete fracture of one element of the truss end link on the mains span section of the eastern leg of the north tower of the bridge, and the partial fracture of its counterpart. The bridge was closed whilst repairs were carried out.

Solution: JF Strainstall deployed a comprehensive health monitoring system to the bridge, including more than 200 strain gauges, temperature and tilt sensors to measure stress in the bridge members. This monitoring enabled the identification of the root cause of the link failure; a seized pin, and a phased repair was implemented as a result of the findings.

M48 Severn Bridge

Hidden defect: Suspension bridge cables

Problem: The client wanted to conduct strain measurement testing on the main suspension cables. 

Solution: JF Strainstall undertook strain measurement testing under live load conditions, conducting measurements on the wires within the main cables.