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

Prevoditelj: Petra Lauš Recezent: Sanda L

In 1990, the Italian government enlisted top engineers

Godine 1990. talijanska je vlada angažirala najbolje inženjere

to stabilize Pisa’s famous Leaning Tower.

da stabiliziraju poznati Kosi toranj u Pisi.

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

Kroz 800 godina postojanja tornja, bilo je mnogo pokušaja da se on ispravi,

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

ali računalni modeli ovog tima otkrili su hitnost situacije.

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

Predvidjeli su da će se toranj srušiti ako se nagne do kuta od 5,44°

and it was currently leaning at 5.5.

i tada je bio nakošen pod kutem od 5,5°.

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

Nitko nije znao kako to da toranj još uvijek stoji, ali kriza je bila očita:

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

morali su riješiti problem koji je zbunjivao inženjere stoljećima

and they needed to do it fast.

i trebali su to napraviti brzo.

To understand their situation,

Kako bi shvatili njihovu situaciju,

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

korisno je razumjeti zašto je toranj uopće nakošen.

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

U 12. stoljeću, bogata pomorska Republika Pisa

set about turning its cathedral square into a magnificent landmark.

krenula je pretvoriti katedralni trg u veličanstvenu znamenitost.

Workers embellished and enlarged the existing church,

Radnici su ukrasili i povećali postojeću crkvu

and added a massive domed baptistry to the plaza.

i dodali veliku krstionicu nadsvođenu kupolom.

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

Godine 1173. počela je izgradnja samostojećeg campanilea ili zvonika.

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

Inženjeri i arhitekti tog vremena bili su majstori svog zanata.

But for all their engineering knowledge,

Ali uza svo njihovo znanje o inženjerstvu,

they knew far less about the ground they stood on.

znali su mnogo manje o tlu na kojem su stajali.

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

Ime "Pisa" dolazi od grčke riječi za "močvarnu zemlju",

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

koja savršeno opisuje glinu, blato i mokri pijesak ispod površine grada.

Ancient Romans counteracted similar conditions with massive stone pillars

Drevni su Rimljani sličnim uvjetima prkosili ogromnim kamenim stupovima

called piles which rest on Earth’s stable bedrock.

koji se zovu piloni i počivaju na stabilnom temelju u Zemlji.

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

Međutim, graditelji tornja mislili su da će temelj od tri metra biti dovoljan

for their relatively short structure.

za njihovu relativno kratku građevinu.

Unfortunately for them, less than five years later,

Nažalost, manje od pet godina kasnije,

the tower’s southern side was already underground.

južna strana tornja bila je već pod zemljom.

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

Temelj koji se toliko pomiče obično bi bio fatalna greška.

If workers added more weight,

Da su radnici dodali još težine,

the pressure from upper stories would sink the structure

toranj bi propao zbog pritiska od viših katova

and fatally increase the lean.

i fatalno povećao nagib.

But construction halted at the fourth story for nearly a century

Ali izgradnja se zaustavila na četvrtom katu na gotovo jedno stoljeće

as Pisa descended into prolonged warfare.

jer je Pisa upala u dugotrajan rat.

This long pause allowed the soil to settle,

Ta duga pauza dala je zemlji da se slegne

and when construction began again in 1272,

i kada je gradnja ponovno počela 1272.,

the foundation was on slightly more stable footing.

temelj je bio na malo stabilnijem uporištu.

Under the direction of architect Giovanni di Simone,

Pod vodstvom arhitekta Giovannija di Simonea

workers compensated for the tower’s minor tilt

radnici su kompenzirali mali nagib tornja

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

tako da su sljedećih nekoliko katova napravili višima na južnoj strani.

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

Ali zbog dodatne težine ta strana je propala još dublje.

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

Do završetka izgradnje sedmog kata i vrha,

the angle of the tilt was 1.6 degrees.

kut nagiba bio je 1,6°.

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

Inženjeri su stoljećima isprobavali brojne strategije da riješe problem nagiba.

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

Godine 1838. iskopali su stazu oko baze kako bi ispitali propali temelj.

But removing the supporting sand only worsened the tilt.

Ali uklanjanje potpornog pijeska samo je pogoršalo nagib.

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

Godine 1935. talijanski korpus inženjera ubrizgao je mort kako bi učvrstio bazu.

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

Međutim, mort nije bio ravnomjerno raspoređen u temelju,

resulting in another sudden drop.

što je rezultiralo još jednim naglim propadanjem.

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

Svi ti neuspješni pokušaji, zajedno s temeljem koji stalno tone,

moved the tower closer to its tipping point.

uzrokovali su da toranj dođe bliže točki prevrtanja.

And without definitive knowledge of the soil composition,

Bez jasnog znanja o sastavu tla,

engineers couldn’t pinpoint the tower’s fatal angle

inženjeri nisu mogli precizno odrediti fatalni kut tornja

or devise a way to stop its fall.

ili osmisliti način kako zaustaviti njegov pad.

In the years following WWII,

Nakon Drugog svjetskog rata,

researchers developed tests to identify those missing variables.

istraživači su razvili testove za identifikaciju varijabli koje nedostaju.

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

Inženjeri su 1970-ih izračunali centar gravitacije nagnutog tornja.

With this data and new computing technology,

Tim podacima i novom računalnom tehnologijom

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

inženjeri su mogli modelirati putanju tornja, tvrdoću tla

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

i koliko je točno potrebno kopati da toranj ostane stajati.

In 1992, the team drilled diagonal tunnels

Godine 1992. tim je izbušio dijagonalne tunele

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

kako bi odstranili 38 kubnih metara zemlje ispod sjeverne strane tornja.

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

Zatim su privremeno napravili protutežu od 600 tona olovnih ingota

before anchoring the base with steel cables.

prije no što su učvrstili bazu čeličnim kabelima.

More than six centuries after its construction,

Više od šest stoljeća nakon izgradnje,

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

toranj je napokon bio izravnat... S kutom nagiba od oko 4°.

No one wanted the tower to fall,

Nitko nije želio da toranj padne,

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

ali također nisu željeli da se izgubi najpoznatije obilježje te znamenitosti.

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

Danas je toranj visok 55 odnosno 56 metara

and it should remain stable for at least 300 years

i trebao bi ostati stabilan još barem 300 godina

as a monument to the beauty of imperfection.

kao spomenik ljepoti nesavršenosti.