By Matthew Doré
TWI performed a programme of inspection and characterisation of electroslag (ES) welds for a UK-based highways maintenance company, on a network-critical structure prior to the London 2012 Olympics.
The multidisciplinary non-destructive inspection of the welds was led by TWI engineers and comprised teams of specialists from different UK-based inspection companies.
The materials characterisation was performed by TWI engineers investigating weld quality, materials properties, residual stresses, fatigue crack growth rates (FCGR) and cyclic response.
Quality assessment of welds
TWI undertook an extensive programme of inspection of ES welds contained within 965m of steelwork, over 17 spans of plate girder flanges and lattice (truss) box girders (Fig. 1).
A range of non-destructive testing (NDT) techniques were used including eddy current, magnetic particle inspection, manual ultrasonic testing, phased array ultrasonic testing and alternating current potential drop.
Many of the weld locations were inaccessible by platforms and so inspection was also performed by roped access.
Approximately 600 ES welds were inspected with multiple techniques applied at each weld location.
Engineering critical assessment
As part of the on-site inspection, TWI engineers instrumented a number of critical locations using uniaxial electrical resistance strain gauges, to record the cyclic response of the structure over a period of three weeks.
Samples of the welds were removed to facilitate in-house tensile testing, fracture toughness testing, FCGR testing, chemical analysis using optical emission spectrometry, Vickers hardness testing and macro-sectioning (Fig. 2).
A rainflow analysis of the cyclic response data, results of materials testing and non-destructive inspection findings were used as input parameters for an engineering critical assessment using TWI’s CrackWise™ integrity management software.
Fig. 1 Lattice (truss) box girder section
Fig. 2 Electroslag weld sample removed for mechanical testing
The combined programme of work allowed TWI to provide independent advice on the structural integrity of ES welds in a critical part of UK infrastructure, required to support unprecedented levels of tourism during the London 2012 Olympics.
To find out more about TWI’s Integrity Management services, contact us. To find out more about CrackWise and other software solutions, visit www.twisoftware.com.
Team Manager - Fatigue Integrity
Matthew joined TWI in October 2000 working in the Fatigue Section and was promoted to Team Manager in 2016. He completed a PhD through the Open University under the supervision of Dr Stephen Maddox investigating fatigue crack growth acceleration and how it can be allowed for in fatigue design.
Matthew has led a variety of consultancy projects for a broad range of industries and specialises in fatigue design and fatigue life improvement. Principal project areas have included the assessment of offshore structures, the structural integrity of bridges, and the fatigue life improvement of welded high-strength steels and welded aluminium alloys. He has authored conference and journal publications on fatigue under variable amplitude loading for steel and aluminium alloy, and fatigue life extension focusing primarily on high-frequency mechanical impact treatment. He is also a committee member serving on panels for BS 7608, BS 7910 and the IIW Commission XIII.