Why doesn’t the Leaning Tower of Pisa fall over? - Alex Gendler

Prevodilac: Milenka Okuka Lektor: Ivana Korom

In 1990, the Italian government enlisted top engineers

Godine 1990, italijanska vlada je okupila najbolje inženjere

to stabilize Pisa’s famous Leaning Tower.

kako bi stabilizovali čuveni Krivi toranj.

There’d been many attempts to right the tower during its 800 year history,

Tokom osamstogodišnje istorije tornja bilo je mnogo pokušaja da se on ispravi,

but this team’s computer models revealed the urgency of their situation.

ali kompjuterski modeli ove ekipe su otkrili hitnost situacije.

They projected the tower would topple if it reached an angle of 5.44 degrees—

Preptostavili su da će se toranj srušiti ako dosegne ugao od 5,44 stepena -

and it was currently leaning at 5.5.

a u tom trenutku se naginjao 5,5 stepeni.

No one knew how the tower was still standing, but the crisis was clear:

Niko nije znao kako toranj i dalje stoji, ali je kriza bila jasna:

they had to solve a problem that stumped centuries of engineers,

morali su da reše problem koji je vekovima zbunjivao inženjere

and they needed to do it fast.

i morali su to da urade brzo.

To understand their situation,

Kako bismo razumeli situaciju,

it’s helpful to understand why the tower tilted in the first place.

od pomoći je da razmemo zašto se toranj uopšte i nakrivio.

In the 12th century, the wealthy maritime republic of Pisa

U XII veku, bogata pomorska republika Piza

set about turning its cathedral square into a magnificent landmark.

se zaputila da trg sa katedralom pretvori u veličanstvenu znamenitost.

Workers embellished and enlarged the existing church,

Radnici su ulepšali i proširili postojeću crkvu

and added a massive domed baptistry to the plaza.

i dodali su trgu ogromnu kupolastu krstionicu.

In 1173, construction began on a free-standing campanile, or bell tower.

Godine 1173, započeta je izgradnja samostalne kampanile tj. zvonika.

The engineers and architects of the time were masters of their craft.

Inženjeri i arhitekte tog doba su bili majstori svog zanata.

But for all their engineering knowledge,

Međutim, uprkos svom tom inženjerskom znanju,

they knew far less about the ground they stood on.

daleko manje su znali o tlu na kom su stajali.

Pisa’s name comes from a Greek word for “marshy land,"

Ime Piza potiče od grčke reči za „močvarnu zemlju”,

which perfectly describes the clay, mud, and wet sand below the city’s surface.

koja savršeno opisuje glinu, blato i vlažni pesak pod površinom grada.

Ancient Romans counteracted similar conditions with massive stone pillars

Drevni Rimljani su izlazili na kraj sa sličnim uslovima

uz pomoć masivnih kamenih stubova

called piles which rest on Earth’s stable bedrock.

nazvanih pilonima koji su stajali na stabilnom zemljinom kamenom tlu.

However, the tower’s architects believed a three-meter foundation would suffice

Međutim, arhitekte tornja su smatrali da će temelji od tri metra biti dovoljni

for their relatively short structure.

za njihovu neveliku građevinu.

Unfortunately for them, less than five years later,

Na njihovu žalost, za manje od pet godina,

the tower’s southern side was already underground.

južna strana tornja je već bila pod zemljom.

Such a shifting foundation would normally have been a fatal flaw.

Takva promena u temeljima bi obično bila fatalna greška.

If workers added more weight,

Ukoliko bi radnici dodali još težine,

the pressure from upper stories would sink the structure

pritisak gornjih spratova bi potopio građevinu

and fatally increase the lean.

i nagib bi bio fatalno uvećan.

But construction halted at the fourth story for nearly a century

Međutim, skoro čitav vek izgradnja je stajala na četvrtom spratu

as Pisa descended into prolonged warfare.

dok je Piza srljala u sve duži rat.

This long pause allowed the soil to settle,

Ova duga pauza je omogućila tlu da se slegne

and when construction began again in 1272,

i kada je izgradnja ponovo započeta 1272. godine,

the foundation was on slightly more stable footing.

temelji su bili na nešto stabilnijoj podlozi.

Under the direction of architect Giovanni di Simone,

Pod vođstvom arhtekte Đovanija di Simonea,

workers compensated for the tower’s minor tilt

radnici su nadomestili manji nagib tornja

by making the next few floors taller on the southern side.

gradeći nekoliko narednih spratova da budu viši sa južne strane.

But the weight of the extra masonry made that side sink even deeper.

Međutim, pod težinom dodatnih zidova ta strana je još dublje tonula.

By the time they completed the seventh floor and bell chamber,

Dok su izgradili sedmi sprat i zvonik,

the angle of the tilt was 1.6 degrees.

ugao nagiba je bio 1,6 stepeni.

For centuries, engineers tried numerous strategies to address the lean.

Vekovima su inženjeri isprobavali razne strategije da isprave nagib.

In 1838, they dug a walkway around the base to examine the sunken foundation.

Godine 1838, iskopali su nogostup oko baze kako bi ispitali potonule temelje.

But removing the supporting sand only worsened the tilt.

Međutim, uklanjanjem potpornog peska, nagib se samo pogoršao.

In 1935, the Italian Corps of Engineers injected mortar to strengthen the base.

Godine 1935, Korpus italijanskih inženjera je ubrizgao malter da ojača osnovu.

However, the mortar wasn’t evenly distributed throughout the foundation,

Međutim, malter nije nanesen ravnomerno duž temelja

resulting in another sudden drop.

što je rezultiralo novim naglim potonućem.

All these failed attempts, along with the ever-sinking foundation,

Svi ovi neuspešni pokušaji, zajedno sa temeljima koji stalno tonu

moved the tower closer to its tipping point.

su gurali toranj sve bliže prelomnoj tački.

And without definitive knowledge of the soil composition,

A bez istinskog poznavanja sastava zemljišta,

engineers couldn’t pinpoint the tower’s fatal angle

inženjeri nisu mogli da odrede fatalni ugao tornja,

or devise a way to stop its fall.

niti da pronađu način da zaustave njegov pad.

In the years following WWII,

U godinama nakon Drugog svetskog rata,

researchers developed tests to identify those missing variables.

istraživači su razvili testove da otkriju nedostajuće varijable.

And in the 1970’s, engineers calculated the curved tower’s center of gravity.

A 1970. godine, inženjeri su izračunali centar gravitacje nakrivljenog tornja.

With this data and new computing technology,

S tim podacima i novom kompjuterskom tehnologijom,

engineers could model how stiff the soil was, the tower’s trajectory,

inženjeri su mogli da procene čvrstinu tla, trajektoriju tornja,

and the exact amount of excavation needed for the tower to remain standing.

kao i tačnu količinu iskopavanja koja je potrebna da toranj opstane.

In 1992, the team drilled diagonal tunnels

Godine 1992, ekipa je iskopala dijagonalne tunele

to remove 38 cubic meters of soil from under the tower’s north end.

kako bi uklonili 38 kubnih metara tla ispod tornja blizu severnog kraja.

Then, they temporarily counterbalanced the structure with 600 tons of lead ingots

Potom su privremeno izbalansirali građevinu sa 600 tona olovnih šipki

before anchoring the base with steel cables.

pre nego što su učvrstili bazu čeličnim kablovima.

More than six centuries after its construction,

Više od šest vekova nakon izgradnje,

the tower was finally straightened… to a tilt of about four degrees.

toranj je konačno ispravljen... do nagiba od oko četiri stepana.

No one wanted the tower to fall,

Niko nije želeo da se toranj sruši,

but they also didn’t want to lose the landmark’s most famous feature.

ali nisu ni želeli da izgube najčuveniju karakteristiku ove znamenitosti.

Today the tower stands at 55– or 56– meters tall,

Danas je ovaj toranj visok 55 ili 56 metara

and it should remain stable for at least 300 years

i trebalo bi da bude stabilan najmanje 300 godina

as a monument to the beauty of imperfection.

kao spomenik lepoti nesavršenosti.