technology&more

technology&more

technology&more

technology&more

technology&more

technology&more

-12- 

 Technology&more

T

here’s a fun story about Palermo’s Teatro Massimo Vittorio 
Emanuele Opera House: According to legend, a nun—
the first mother superior of the convent over which 

the opera house foundation was laid in 1875—still wanders 
through the building. The legend also says that anyone who 
does not believe in the nun’s spirit will trip on a step at the 
entrance to the Massimo.

The historic opera house, which opened in 1897, is the largest 
in Italy and the third largest in Europe. With five rows of boxes 
and a gallery, the theater can seat up to 3,500 people. One of 
its distinctive features is an enormous hemispherical cupola 
23.7 m (77.7 ft) in diameter. A series of 16 steel arches sup-
ports the cupola. Each arch rests on mobile bogies, which 
are placed on a masonry edging.

A Flexible Structure 
Palermo’s temperature variations can be extreme; summer 
days can easily reach 40° C (104° F). This puts the Massimo 
cupola to the test as temperature gradients cause the steel 
arches to expand. To accommodate the movement, the build-
ing’s original architects devised the system of bogies to absorb 
the movement and relieve structural stress. 

More than 100 years after they were constructed, engineers 
needed to check the effectiveness of the bogies—their mobility, 
and therefore the stability of the cupola itself. The Department 

of Civil, Environmental, Aerospatial and Materials Engineering 
(DICAM) of the University of Palermo—Massimo Allegra, Gino 
Dardanelli, Valeria Giammaresi and Pietro Orlando—undertook 
the task of determining how much the arches moved with the 
temperature changes. 

Planning for Precision 
After an initial inspection, it was clear to the DICAM team that 
the surveying operations would not be simple. In addition 
to requirements for sub-millimeter precision, the survey pre-
sented considerable logistical challenges. The bogies rested on 
a 4 m (13 ft)-high masonry ledge. In spite of being 1.1 m (3.6 ft) 
wide, the ledge provided only a narrow place for a person to 
stand. In addition, the ledge was accessible by a small stairway 
in only one area; to reach the other bogies, scaffolding would 
be needed. 

The team selected Trimble S8 total stations to conduct the 
measurements. The first task was to determine where to set 
up the station points. By carefully selecting the station points, 
the team could use the automated instruments to achieve 
sub-millimeter precision on even the difficult-to-access points. 
This would make it possible to collect data over long periods 
of time.

The team set two station points at diametrically opposite loca-
tions on the ledge. Technicians installed circular metal plates to 

Measuring the Massimo