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STRUCTURESTHAT OUTPERFORMBY J E N N I F E R S O W ABENDING, SQUEEZING, STRETCHING, FREEZING: PUSHINGMATERIALS TO THEIR LIMITS IS NOW REQUIRED TO DEVELOPMODERN STRUCTURES AND PRESERVE OLD ONES.Australia’s southernmost state ishome to a 50-metre sandstonebridge nearly two centuries old that is abit of an engineering marvel in this littlecorner of the world.The Ross Bridge was constructed overthe Macquarie River in the 1830s whenthe island state of Tasmania was a penalcolony for British criminals. Convictswere put to work building the bridge andsome of them happened to be talentedartists and stonemasons. The result was astructurally impressive bridge decoratedwith dozens of intricate carvings ofsymbols, flowers and human faces.Two prisoners actually received pardonsbecause of their extraordinary work.The Ross Bridge supports vehicular trafficto this day and has become known as“the finest masonry bridge of its time,”according to the Australian HeritageDatabase.“We are very proud of the Ross Bridgeas an outstanding and unique exampleof early colonial infrastructure thatcontinues to be used to the presentday,” says Pete Smith, director ofHeritage Tasmania.It was a bridge built to last. But while itshistory makes it unique, the Ross Bridgehas one trait in common with countlessother structures: it’s at the mercy ofthe elements. Weathering is erasing thetreasured carvings like drawings on achalkboard. Many experts fear all the finedetail will be gone in 25 years.It won’t be lost forever, though, becauseof modern engineering technology.Four years ago, specialists in threedimensionallaser scanning mappedthe Ross Bridge. Derek Lichti, a formerprofessor at Curtin University ofTechnology in Perth, Australia, andhis graduate student developed newcomputer algorithms to take informationfrom the digital scans to form acomplete, detailed image of the bridge.One day, that data will provide crucialguidance for the experts who restoreand preserve the bridge and its artwork.“The scans give you the precise geometryof the bridge,” explains Lichti, who is nowbased in the geomatics department at theSchulich School of Engineering. “Whenyou consider additional informationsuch as the material, in this case it’ssandstone, you can figure out thestructure’s strength properties.” >>Photo by David MollSCHULICH21ENGINEER