Church of S. Marta in Arona: conservative restoration of the wooden trusses to stabilize the structure

The choice of a conservative consolidation approved by the superintendent

For the safety of the church and to protect the restoration work from unforeseen events, the Works Director has decided to resolve the anomalies found.

He relied on the company Sicurtecto Srl, which he developed the conservative solution for the consolidation of trusses: Resistecto ®. Resistecto® is a system that integrates with the existing truss to give stability to the roof, rebalance the forces and resolve structural critical issues.
It is made up of flanges that embrace the existing wooden elements and connection elements that are custom configured to rebalance the stresses.

This system has been designed to respect the existing trusses: it does not require holes in the trusses, it is reversible and does not weigh down the structure. Above all, it does not provide for replacements and preserves the original wooden elements.

Intervening with a conservative consolidation was fundamental for the church of Arona, as it is a listed asset. The Superintendence immediately gave the approval to proceed with Resistecto®That he replies in fact to all conservative restoration requirements.

The phases of consolidation: from diagnostics to customized solutions

Each Resistecto® intervention involves different phases, all performed by certified staff internal which uses specific instrumentation and software created ad hoc to obtain objective results with a consolidated process.

First, the teams evaluated the trusses of the S. Marta church with diagnostic analyses instrumental and coverage modeling. From here they verified the behavior of the trusses, confirming the presence of critical issues:

• absence of braces: no protection in case of strong winds or earthquakes;
• instability of the monk: the monk was out of plan with respect to the truss, highlighting kinematics;
• pushing trusses: the struts were lowering compared to their original configuration and were pushing the walls on which they rest outwards, risking the facades overturning. The checks confirmed that the cracks initially visible on the walls of the church were due to the trusses that were pushing outwards.

This diagnostic phase made it possible to limit the critical issues on which to intervene and design a local intervention compliant with NTC 2018. The objective was to secure the trusses from one point of view static and seismic. Based on this, the team designed Resistecto® according to different configurations:

• bracing lines which eliminate the overturning of the trusses out of plane;
• freezing lines of the monks out of plane of the trusses and lines of stabilization of the nodes;
• containment lines of chains to cancel the thrusts on the perimeter walls, both in the trusses and on the pushing struts of the perimeter interfaces, thus eliminating the problem of the pushing roof.