Researchers at the University of Sheffield have developed a new engineering technique that could help to preserve historic stone buildings and bridges.
The researchers, from the university’s Department of Civil and Structural Engineering, say the method provides a new, more accurate way of assessing how stone and brick masonry constructions – including medieval cathedrals and Victorian railway viaducts – can safely carry applied forces.
They have also developed open source software that, with further development, will allow practicing engineers and architects to assess the safety of stone and brick masonry constructions.
The new approach could mean more masonry structures are restored and used long into the future, they say, rather than demolished and replaced.
Since the late 1600s, engineers have used the ‘thrust line method’ to assess the safety of masonry buildings and bridges, developed by famous scientist Robert Hooke.
The traditional thrust line method has limitations, however.
For example, it requires an engineer to exercise precise judgement when assessing the safety of masonry constructions containing openings.
It also neglects the possibility of failure due to sliding.
Furthermore, it is often not clear which areas of masonry are required to possess some tensile capacity (the ability to be stretched or pulled before breaking).
The Sheffield researchers say their new approach overcomes these limitations and that it can be applied to masonry constructions of any geometry, with or without openings.
The technique, called ‘thrust layout optimisation’, also explicitly highlights regions in structures where some tensile capacity is needed.
‘Resurgent interest’ in stone
Research team leader Matthew Gilbert, professor of Civil Engineering at the University of Sheffield, said: “Stone and brick masonry has been used for millennia to form buildings and bridges ranging in scale from humble dwelling houses to cathedrals and railway viaducts.
“Many of these structures have considerable historic value, and, to ensure they remain safe and fit for purpose, effective assessment methods are required.”
He continued: “A long-running problem is that the ways in which applied forces are successfully transmitted down to the ground in masonry structures are often not intuitively obvious, so digital tools that help explain this to engineers are potentially invaluable.
“The current climate crisis also makes it particularly important that engineers have access to efficient and reliable tools to assess the safety of existing masonry constructions – helping to ensure that these can be used long into the future, rather than being needlessly demolished and replaced.”
Lead author Isuru Nanayakkara, a research student at the University of Sheffield, said: “There has been a resurgence in interest in using stone in construction, as it’s a low-embodied-carbon material.
“However, suitable digital analysis and design tools are needed to translate this interest into more widespread use.
“Currently, engineers have been turning to analysis and design tools that are better suited for steel and concrete structures, which means that steel reinforcement is sometimes being used in new masonry designs when it’s not needed.
“We hope that our new thrust layout optimisation technique can help here – we’re making available open-source software for interested structural engineers and architects and we welcome their feedback on this.”
Image: Rob Crandall/Shutterstock
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