Sunday, April 22, 2012

fixing the Juillac bridge

A couple weeks ago they closed the suspension bridge between Prayssac and Juillac for a few days for repairs.  La Depîche, the regional rag, duly wrote up everything the bridge guys said, how it wasn't really serious, no danger to the public at this time, can't be too safe.  "A slight anomalie" at the base of a cable.  I was out on a ride above Prayssac but detoured through over the Juillac bridge just to see the repair.

Leaving Prayssac, you coast down a hill past a landscape of beautifully organized cultivation:  walnut and fruit orchards aligned in rows and columns so perfect that the diagonals line up too.   The bridge crosses a stretch of strong, flat water about midway between the dam at Castelfranc upstream and Belaye downstream, free of the turbulence from above but not yet rendered comatose by the ecluse to come.  This gorgeous valley must have amazed each of the successive plunderers, Gauls, Celts, Romans, then the Vandals and the Wisigoths and eventually the English.  




The mathematical perfection of this bridge brings you right back up to maybe 1880.  There was probably a ferry here at first.  To build the bridge, they must have first set up the four columns, then established the  four heavy deep-set concrete stays, then run the cables from stay to column to column to stay.  Big spool of wire, the first strand carried by a boat from one shore to the other.  Back and forth until the formula was satisfied, then the whole mess of cable jammed together with a final, spiral sheath of wire.      






The repair seemed to consist in taking the strain off of the first part of one cable.  First 12 massive clamps were bolted around the cable to resist the top part of the huge steel splint.  The splint was tensioned like the old fashioned traction machines to make broken bones heal correctly.  Once tensioned, the compromised part of the cable can just relax.