Innovative thinking leads to 3D modelling as a tool to investigate bridge scour
Image: 3D mesh of Stanmore Road Bridge, used in CFD model, looking north (downstream)
05 March 2019
pitt&sherry’s Martin Jacobs is a Principal Hydraulics Engineer and has
contributed to the new
DTMR Bridge Scour Manual providing specialist
knowledge of the use of computation fluid dynamic (CFD) or
3D modelling
as a tool to investigate
bridge scour, and to design appropriate
scour
protection measures.
This manual can be downloaded here,
https://www.tmr.qld.gov.au/business-industry/Technical-standards-publications/Bridge-scour-manual.aspx
Image: Map of bed shear stresses, looking north (downstream). The high bed shear stresses are shown in red and correspond to areas where scouring actually occurred.
A survey of bridge failures in the US found that the number one primary cause was flooding and scour, which accounts for just over half of all bridge closures and collapses. Despite the high risk of scouring failure, the tools used to assess and design for scouring had not been well developed. It was clear that an innovative approach was needed, using CFD modelling to map bed shear stresses. Several academic papers had been published that had applied CFD to idealised situations, but no one had attempted to apply CFD modelling to a real bridge failure to prove whether it yielded realistic results.
Image: Alan Wilke (Stanmore Road) Bridge under
flood, 2016, looking east (image from City of Gold Coast)
The opportunity to test the
technology arose through the scouring failure of the Alan Wilke
(Stanmore Road) bridge in
Queensland, 2016. The bridge embankment had failed on the upstream
face on the inside of a bend. Martin approached the bridge owners, the
City of Gold Coast, and gained permission to use the data in a forensic
analysis. Martin’s colleague in pitt&sherry, Kyle
Thomson, volunteered much of his own time to set up the models and
crunch the numbers. Significantly, the result showed high bed shear
stresses in the areas where scouring had actually occurred, proving that
CFD modelling could yield realistic results. The methodology has since
been applied to the design of scour protection for several
bridges in Papua New Guinea, where high flows and poor soils combine
to increase the risk of scour significantly.
The lessons learned formed the basis of Martin’s contributions to the
Government of Queensland’s Bridge Scour Manual, Supplement to
Austroads Guide to Bridge Technology, Part 8, Chapter 5: Bridge Scour
(2018)
--ENDS--
Source: pitt&sherry - www.pittsh.com.au
Contact: https://www.pittsh.com.au/contact-us/
External Links:
DTMR Bridge Scour Manual: https://www.tmr.qld.gov.au/business-industry/Technical-standards-publications/Bridge-scour-manual.aspx
Survey of bridge failures in the US, http://www.engineersjournal.ie/2018/04/03/why-do-bridges-fail/
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