Hell, even in the 5th century or before, they'd have had enough experience to know that bamboo of certain size would be appropriate or not. Sure, they might not

Hell, even in the 5th century or before, they'd have had enough experience to know that bamboo of certain size would be appropriate or not. Sure, they might not now the exact tensile strength in Netwons or lbs/in or whatever unit, but they'd have enough experience to know that to make a bridge for an ox to cross would need certain sizes of bamboo. Even if that knowledge came from losing an ox or two, it would have been learned quickly enough.