Group 10 – Disaster ProjectLeaning Tower of Pisa

The most successful disaster… Ever!

Introduction

• Construction began in August 1173, originally intended to be a marble campanile or bell tower to accompany adjacent Cathedral.

• Discrepancy about who was original architect, not actually known many candidates.

• Widely believed design modelled on Islamic Minarets.• Famous ‘lean’ began in 1178 upon completion of third floor, construction

stopped for almost a century at this point.• 1272 four more floors completed, before final completion in 1372 with addition

of Bell chamber, taking 199 years from start to finish.• 55 metres tall, weighs 14,500 tons containing 296 steps.• 1838 circular walkway around base excavated, exacerbating lean.• Next man to try to solve problem none other than Benito Mussolini.• In 1990 tower closed to public for strengthening works.• Re-opened in 2001 to the public and deemed safe for next 200 years.

Stages of Problem

1. 1178 lean ¼ deg. North– Soil settlement

2. South Walls extended – 5th floor by 16 cm , 6th/7th floor by 3 cm– 1284 Lean south by about 0.6 degree.

3. 1360 lean 1.6 deg. South– South wall extended by 45 cm on edifice

4. 1838 the base was dug out– exposing the buried foundation steps and

column plinths.– below the water table on the south side– inrush of water, which added a half degree to

the lean

What Went wrong

• Insufficient Foundations; only 2.70m deep, no foundation piles, reason most likely high GW level

• Poor Soil; built upon a dense clay mixture • Bad Design; compensating by making floors

higher increased lean in the long run • Foundation Flooding; in 1838 when base was

dug out

Solution attempts:

• Heavier Materials,

• Bend the tower;

• Counter-weight

• Steel Cables

Solution: What Finally Worked

• New Approach,

• Steel Cables,

• Soil extraction.

Despite best attempts to knock it down, engineers finally saved the leaning tower of

Pisa!