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Built to Last: How Ancient Roman Bridges Can Still Withstand the Weight of Modern Cars & Trucks

Built to Last: How Ancient Roman Bridges Can Still Withstand the Weight of Modern Cars & Trucks


A for­eign trav­el­er road-trip­ping across Europe might well feel a wave of trep­i­da­tion before dri­ving a ful­ly loaded mod­ern auto­mo­bile over a more than 2,000-year-old bridge. But it might also be bal­anced out by the under­stand­ing that such a struc­ture has, by def­i­n­i­tion, stood the test of time — and, for those with a grasp of the his­to­ry of engi­neer­ing, that its ancient design­ers would have ensured its capac­i­ty to bear a load far heav­ier than any that would have crossed it in real­i­ty. With no sci­en­tif­ic means of mod­el­ing stress­es, as clas­si­cal-his­to­ry Youtu­ber Gar­rett Ryan explains in the new Told in Stone video above, they just had to build it tough.

Key to that tough­ness were arch­es, “made of heavy blocks laid over a false­work frame until the key­stone was slot­ted into place.” From the late first cen­tu­ry, stonework was sup­ple­ment­ed or replaced by brick and Roman con­crete, a sub­stance much-fea­tured here on Open Cul­ture.

We’ve also cov­ered the Roman bridges you can still cross today: Spain’s Puente de Alcán­tara (from the Ara­bic al-qanţarah, mean­ing “arch”), for exam­ple, which, though crossed by a quar­ter-mil­lion vehi­cles every year, “shows no signs of fail­ing”; or France’s Pont des Marchands, which “has sup­port­ed a neigh­bor­hood of mul­ti-sto­ry shops and hous­es since the Mid­dle Ages.”

But the arch­es of the near­ly 1,000 whol­ly or par­tial­ly sur­viv­ing Roman bridges haven’t done all the work by geom­e­try alone. “The load-bear­ing capac­i­ty of a bridge depend­ed both on the solid­i­ty of its abut­ments and the strength — ‘shear­ing point’ — of its vous­soirs,” or the stones of its arch­es between the key­stone at the top and the springers at the bot­tom. “Since Roman builders carved vous­soirs from the strongest read­i­ly avail­able stone, their bridges tend­ed to be impres­sive­ly sol­id.” You would­n’t want to run a freight train across the Puente de Alcán­tara, but 40-ton trucks are no prob­lem — to say noth­ing of a car filled with lug­gage, a few kids, and even a dog or two.

Relat­ed con­tent:

The Roman Roads and Bridges You Can Still Trav­el Today

The Mys­tery Final­ly Solved: Why Has Roman Con­crete Been So Durable?

The Beau­ty & Inge­nu­ity of the Pan­theon, Ancient Rome’s Best-Pre­served Mon­u­ment: An Intro­duc­tion

Why Hasn’t the Pantheon’s Dome Col­lapsed?: How the Romans Engi­neered the Dome to Last 19 Cen­turies and Count­ing

The Roads of Ancient Rome Visu­al­ized in the Style of Mod­ern Sub­way Maps

Roman Archi­tec­ture: A Free Online Course from Yale

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. His projects include the Sub­stack newslet­ter Books on Cities and the book The State­less City: a Walk through 21st-Cen­tu­ry Los Ange­les. Fol­low him on Twit­ter at @colinmarshall or on Face­book.





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