Leaning tower of Pisa, Italy facts and figures along with its construction history and attempts made to reduce the unintended tilt of the tower.

1. Presented By
Things Simplified
( A New Perspective )

2. 
 Tower of Pisa is a freestanding bell tower of the Cathedral of Pisa, Italy which
stands 60m tall (conceptual), 15-17m in diameter and weighs around 14,500
metric tons.
 It is known world wide as leaning tower of Pisa because of its unintended tilt.
The person or architect who built this structure is still a mystery.
 The tower consists of total 8 stories out of which last one is a bell chamber.
There are total of 207 columns distributed over eight stories. The bottom
storey consists of 15 marble arches. Each of the next six stories contains 30
arches that surround the tower. The final storey is the bell chamber itself, which
has 16 arches.
 There is a 297 step spiral staircase inside the tower leading to the top of the
tower.
Tower of Pisa

3. 
 There are a total of seven bells in bell chamber each having different weight in
order to counter the unintended tilt of the tower.
 1st bell: L'Assunta, weight 3,620 kg (7,981 lb)
 2nd bell: Il Crocifisso, weight 2,462 kg (5,428 lb)
 3rd bell: San Ranieri, weight 1,448 kg (3,192 lb)
 4th bell: La Terza (1st small one), weight 300 kg (661 lb)
 5th bell: La Pasquereccia or La Giustizia, weight 1,014 kg (2,235 lb)
 6th bell: Il Vespruccio (2nd small one), weight 1,000 kg (2,205 lb)
 7th bell: Dal Pozzo, weight 652 kg (1,437 lb)
Tower of Pisa (Cont.)

4. 
 The tower was constructed in three phases.
 The first phase lasted from 1173 to 1178. In this phase first four floors were
built. After the completion of first phase of construction the tower began to
settle and lean northwest due to mere three metre foundation resting on soft
and unstable soil.
 Following an almost 100 year halt due to series of wars in which Pisa was
engaged, in the second phase of construction, three additional floors were
constructed between 1272 and 1278.
 The final phase of construction lasted from 1360 to 1370 over which the bell
chamber was added to the tower top.
Construction of Tower

6. 
 After the completion of first phase of construction the tower had begun to lean
northwest due to presence of soft and unstable subsoil.
 During the second and third phases, the angle of inclination increased and the
principal direction of tilt shifted first to the northeast and then to the south.
 The leaning tower of Pisa was supposed to be 60 meters tall (196.85 feet). After
the lean, however, the highest side of the tower reaches a mere 56.67 meters
(about 186 feet), while the lowest side is 55.86m, or 183 feet.
History of Tilt of Tower

7. 

8. 
 Attempt1 - First ever effort was made in 1935, wherein it was decided to seal
the foundation of the tower by cement grouting but it only worsened the
condition by increasing the tilt of tower.
 Attempt2 - In 1992, the first story was braced with steel tendons, to relieve the
strain on the vulnerable masonry.
 Attempt3 - In 1993, 600 tons of lead ingots were stacked around the base of
the north side of the tower to counterweight the lean.
Attempts to Correct tilt

9. 
 Attempt4 - In 1995, the restoration team opted for 10 underground steel
anchors, to invisibly yank the tower northwards. The anchors were to be
installed, 40 meters deep, from tensioned cables connected to the tower’s
base. In view of Pisa’s high water-table, the team froze the underlying ground
with liquid nitrogen before any anchors were installed, to protect their
excavations from flooding. However, it was not taken into account that water
expands when it freezes. The groundwater pushed up beneath the tower and,
once the freezing had ceased, created gaps for further settlement of the tower.
On the night of September 7, 1995, the tower lurched southwards by more
than it had done in the entire previous year. The team was summoned for an
emergency meeting and the anchor plan was immediately abandoned and
another 300 tons of lead ingots were added in a desperate attempt to prevent
the loss of the tower.
Attempts to Correct tilt
(Cont.)

10. 
 Final Attempt - The final scheme was ‘under excavation’ in which forty-one
inclined boreholes were drilled on the northern side starting with guide tubes
fixed on an R.C. beam. Extraction was carried out using helical augers.
 The aim was to achieve a reduction in the Tower’s inclination by 1800 seconds
of arc (1 degree of arc = 3600 seconds of arc). The work was started on 21-2-
2000 and completed on 19-1-2001 when the total extracted volume of soil
reached 37 m3 and the inclination was reduced to nearly 1620 seconds of arc.
The tower continued its rotation northwards and in July 2001 the total
reduction in inclination reached 1842 sec. which corresponded to a reduction
of 446 mm.
Final Solution for
Correcting Tilt

11. Any Query, ask
in
comments

12. Thanks for your
Attention
Have a Nice Day

13. 
 Reason behind Leaning of Tower of Pisa
https://www.youtube.com/watch?v=kUGJlxIAU0Q
 Documentary on Leaning Tower of Pisa
https://www.youtube.com/watch?v=3gTq4WggLp0
Video References