Politicians and Engineers Join Forces to Save the Leaning Tower of Pisa
Gianella Sornoza, Biology/Spanish, and Christopher Vargas, Mechanical Engineering
Union College, Schenectady, NY 12308
Advisor
Ashraf Ghaly, Ph.D., P.E., Professor
Engineering Department, Union College, Schenectady, NY 12308
The Leaning Tower of Pisa is one of the most recognizable historical buildings in the world. The leaning of the tower started almost immediately after the construction began due to weak soil conditions beneath one side the foundation. This tower was built over a span of five centuries and on two stages with seventy years of stoppage time in between. After the completion of the first phase, builders noticed the leaning of the first three floors. In an attempt to compensate for the difference in elevation, the five added floors and the bell tower were of differentiating heights, which gave the tower its present banana shape. At the time of completion in 1370, the lean was approximately 3.5 degrees from the vertical. The lean reached 5.4 degrees by 1911 and increased to 5.5 degrees by 1990. The Fascist Italian leader Benito Mussolini considered demolishing the tower as he regarded its tilt to be a blemish that stained the Fascist ideals. In 1934, engineers tried to right the tower by impregnating the base with concrete. This had an adverse effect and added to the tilt. In 1950 the seven bells were silenced for fear that vibrations may trigger a collapse.
The Italian government formed seventeen commissions to study the stability of the ever-increasing lean of the tower. Sixteen of these commissions produced volumes of analysis enough to fill a library. In 1989, after the sudden collapse of a contemporary, perfectly vertical Tower of Pavia, the Italian government was jolted into taking a decisive action. The government constituted the 17th commission and hired a consortium of five Italian contractors and design firms. The parliament granted the commission powers to do “what it takes” to save the tower. These powers were granted for only six months and required a vote for renewal. This was not done without considerable political wrangling. The 17th commission came up with an innovative solution but that required the approval of the politicians who lacked the expertise to judge.
The goal of this paper is to demonstrate how only after the full cooperation of the politicians and the engineers was it possible to arrest the leaning of the tower and to slightly reverse it. This presentation will include modeling of the tower and its structural components to show the areas subjected to great compression and tension. The stabilization work completed in 1999 will extend the life of the tower by an estimated 300 years.