How did bridge builders of old ensure both ends of the bridge would perfect meet in the middle before laser measuring was around?
In: Engineering
Bridges aren’t as precisely sized as you think even today, physics won’t let them be
The longest span on the new Tappan Zee is 370 meters long and can change length by 20 cm between a hot summer day and a cold winter day. Bridges are built with expansion joints which let them expand/contract as temperatures change and also take up some slack during construction
With old stone bridges a lot of stones were adjusted for their spots. Have a smaller gap than expected when you get to the middle? Smack the stone with a hammer until it fits! Then add some mortar to take up all the slack. Voila! A bridge that “meets perfectly” in the middle
Our precision measurements let us better understand the load capabilities of structures and make parts in advance so we can build them faster, but every engineering design supports some slop in the final measurements
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