Straight-talk­ing en­gi­neers at­tempt to right grav­i­ta­tion­ally chal­lenged tower

China Daily (Latin America Weekly) - - Front Page - AGENCE FRANCE- PRESSE AGENCE FRANCE- PRESSE

PISA, Italy — “It’s still straight­en­ing,” said en­gi­neer Roberto Cela, gaz­ing at the Lean­ing Tower of Pisa gleam­ing in the au­tumn sunshine of north­ern Italy. “And many years will have to pass be­fore it stops.”

The grav­i­ta­tion­ally chal­lenged land­mark is lean­ing less af­ter years of am­bi­tious en­gi­neer­ing work. For­tu­nately for the mil­lions of tourists who come here ev­ery year, the 57-me­ter tower re­mains beau­ti­fully askew.

The medieval bell tower, a sym­bol of the power of the mar­itime repub­lic of Pisa in the Mid­dle Ages, has leaned to one side ever since build­ing started in 1173 on ground that proved a lit­tle too soft.

The tower was closed to the pub­lic in Jan­uary 1990 for 11 years over safety fears, as its tilt reached 4.5 me­ters from the ver­ti­cal, threat­en­ing to turn it into a pile of rub­ble.

“We in­stalled a num­ber of tubes un­der­ground, on the side that the Tower leans away from,” said Cela, tech­ni­cal di­rec­tor at the OPA, which looks af­ter Pisa’s main mon­u­ments.

“We re­moved soil by drilling very care­fully. Thanks to this sys­tem, we re­cov­ered half a de­gree of lean,” he said.

Michele Jami­olkowski, an en­gi­neer of Pol­ish ori­gin, co­or­di­nated an in­ter­na­tional com­mit­tee to res­cue the land­mark be­tween 1993 and 2001.

En­gi­neer­ing lec­turer Nun­ziante Squeglia of Pisa Univer­sity, who works with the Sur­veil­lance Group that was set up af­ter the res­cue work, has been study­ing and mea­sur­ing the tower for 25 years.

He says that the tower straight­ened by 41 cen­time­ters un­til 2001, and an­other 4 cm since then.

To un­der­stand how the 14,500- ton build­ing is mov­ing, mea­sure­ments are made as of­ten as once an hour, some us­ing pen­du­lums, some us­ing a sur­veyor’s op­ti­cal level.

“The tower tends to de­form and re­duce its lean in the sum­mer, when it’s hot, be­cause the tower leans to the south, so its south­ern side is warmed, and the stone ex­pands. And by ex­pand­ing, the tower straight­ens,” said Squeglia.

He ex­plains that there are three pen­du­lums, one dat­ing back to 1935, when sys­tem­atic mea­sure­ments be­gan, al­though an­nual mea­sure­ments be­gan as far back as 1911.

Mean­while, Cela pre­dicted that the tower “will never be com­pletely straight”.

“When they were build­ing it, there were at­tempts to straighten it (by adding stone on one side), so it has a slight ba­nana shape.”

Sin­ga­porean tourist Alvin, who like many vis­i­tors is tak­ing pho­tos of friends “hold­ing up” the tower in the back­ground, said he didn’t know about the de­creased lean.

“Oh, I didn’t no­tice, is it be­cause ev­ery­one’s push­ing against it?” he said, promis­ing to try to push the tower back if it straight­ens too much.

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