ALGOR SOFTWARE HELPS RENOVATE HISTORIC ITALIAN CHURCH

The Church of S. Giovanni Battista in Farigliano, Italy has been analyzed using Algor software, and repairs are planned based on the analysis results.

Algor Around the World: Italy

In 1988, the Church of S. Giovanni Battista in Farigliano, Italy, was closed to the public after basement flooding caused severe damage. It was then that Giuseppe Pistone, who is also an architecture professor at the Politecnico di Torino in the Dipartimento di Ingegneria Strutturale (Polytechnic of Turin, Department of Structural Engineering), began using Algor software to study ways to save the structure and make it safer.

An Historical Structure

The Church of S. Giovanni was constructed in only two years in the wake of an 1887 earthquake that irreparably damaged the previous parish church in Farigliano.

In the haste to provide a church for the townspeople, the current building was erected on foundations dug in soft soil and recently deposited materials. The ground had been excavated and oak piles were used to support isolated foundation columns, but these measures did not prove sufficient.

"Documents from the church archive show that the site had been selected for various reasons. Unfortunately, none of these reasons were of a technical nature," said Professor Pistone.

From the outset, diffused fissures appeared in the thin vaults of the side naves and cracks formed in the vertical walls. In 1988, one hundred years after construction was begun, the church was closed to the public after basement flooding further weakened the structure. The risk of collapse loomed as the vertical structures settled further.

A Classic Structure

The church is classically designed in the shape of a Latin cross with a dome at the transept. The sturdy presbytery walls in the rear of the church more than adequately support the dome structure.

However, the slender columns and thin vaults in the front of the building have not offered sufficient support. Over the years these structures have deformed, and the dome is rotating vertically, sinking into the front of the church.

The weight of the dome also rests on the side facades, which behave as slabs subjected to bending. They have "bellied out" causing fissures throughout the sides of the building.

Professor Giuseppe Pistone (right) at the Politecnico di Torino in Italy performed the study on the Church of S. Giovanni Battista in Farigliano. He was assisted by D. Zorgniotti (left).

Assessing the Damage

A consolidation project was initiated to collect data about the church structure and take measures against further damage. The plan was to use the data to construct a series of finite element models. The forces on the structure would be modeled to determine solutions to the church's instability.

In June of 1991, a hydraulic leveling system was installed. Since then, it has been operating continuously collecting data on differential settlements at significant points of the building.

The first major protective measure was to underpin the foundation with micro-piles. Vertical piles were connected to the masonry foundation through reinforced concrete slabs. The piles were driven through softer soil down into stiff clays 17 meters below ground level.

"Data collected from the hydraulic leveling system indicated that after the micro-piles were in place, the structure did not suffer from any further movement," reported Professor Pistone.

The Analyses

Professor Pistone and D. Zorgniotti, performed several trial runs with different models. They concluded that the best model for analysis was a compound plate/beam element model. On such a large and complex model, plates and beams offered reduced disk space usage.

A nonlinear analysis involving gap elements was executed to reproduce the cracking and structural collapse that had already occurred. Several iterations were completed, but a total reconstruction of the church's accumulating damage over the last century proved impossible due to lack of information.

Several trial analyses were conducted before Professor Pistone chose this plate and beam element model as the most efficient type for his analysis needs.

The Results

The original assumption was that the structural damage was due solely to foundation settlements. However, the analyses of the model of the original building showed that some of the damage could be attributed to the design of the structure. Namely, the front part of the building was not endowed with sufficient stiffness.

"In actual fact, lesions appeared precisely in the zones where finite element analyses revealed tensile stresses were present," said Professor Pistone.

This picture shows the front of the interior of the Church of S. Giovanni Battista.

Future Plans

The micro-piles have thus far stabilized the foundation of the church, but the structural weaknesses have yet to be addressed. A second stage of repairs will restore the integrity of the damaged building and correct the deficiencies revealed by the finite element analyses.

Modifications will include strengthening the existing vaults, especially those along the aisle. The entire upper part of the central nave will be modified through the application of a huge frame to be concealed under the existing structures.

A metal bar mesh will be placed under the masonry to strengthen it, while sturdy metal beams will be fitted on top of the lacular roofing and restrained in the two vertical walls.

Originally, the town of Farigliano had planned to fund the renovations because the structure is an historic landmark. However, since these funds have not been made available, the church members have had to find other means. In May 1995, the money needed was finally raised. Construction will begin in the near future.

With the help of Algor FEA, Professor Pistone and the community in Farigliano have been able to overcome the effects of time, the elements and construction problems on the Church of S. Giovanni Battista.

Finite element analyses of the church in Farigliano revealed that excessive stresses to the sides and supports of the building were partially to blame for cracks in those areas.

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