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Rubrica 3 COSE CHE NON SAI - Restauro Storico
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3 Things You Don’t Know About Historic Building Restoration: Techniques and Specialized Investigations

By Daniele Ridolfi,

Techniques and Investigations in the Restoration of Historic Buildings

Through extensive experience working on protected historic buildings, we have found that many design decisions originate from technical details that are often little known, yet crucial to the quality and technical correctness of the intervention.

What is sagramatura?

Sagramatura is a specific traditional finishing technique observed on the construction site of the Convent of Matelica. It involves the abrasion of brick surfaces; the resulting powder is then mixed with water and lime putty to create a highly fluid, homogeneous mortar, which is applied to the masonry surface.

How to choose the appropriate intervention: structural strengthening or replacement of timber elements?

Within the scope of restoration and enhancement works on existing buildings, when assessing timber roof elements, visual inspection alone is sometimes insufficient. More extensive and targeted investigations are required, including resistograph testing, moisture measurements, and analyses to identify the wood species. The resulting data are then used for structural calculations to determine whether timber elements such as purlins or truss members should be replaced or structurally strengthened.

What types of ground investigations are most suitable for protected historic buildings?

In the context of a historic building construction site, preliminary investigations are required prior to the start of any intervention. Ground-penetrating radar (GPR) surveys are generally carried out to identify potential voids or cavities beneath the walking surface. In addition, penetrometric tests may be performed to further investigate the mechanical properties of the soil before installing the crane.

Oltre la verticalità come nascono i pilastri inclinati del complesso residenziale di Busto Arsizio
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Beyond Verticality: How the Inclined Columns of the Busto Arsizio Residential Complex Were Built

By Daniele Ridolfi,

A New Architectural Landmark Between Via Marsala and Via Pergolesi

In the heart of Busto Arsizio (VA), between Via Marsala, Via Pergolesi, and Via Petrella, a new mixed-use complex is taking shape — a contemporary architectural structure combining residential and office functions.
Commissioned by Live Green Palace S.r.l., the project consists of two independent buildings, each with distinct functions and volumes.

The first block, developed perpendicularly to Via Pergolesi, includes one underground floor and three above-ground levels dedicated to parking and office spaces.
The second block, on the other hand, is the symbolic heart of the project — a volume completely detached from the ground, suspended in mid-air and connected to the lower block only through the staircase core and two elevator shafts.
Rising six stories above ground, it hosts residential units with wide terraces and a flat roof equipped with photovoltaic panels, combining structural rigor with a sense of architectural lightness.

Un nuovo segno architettonico tra via Marsala e via Pergolesi

The Suspended Block: Nine Inclined Columns

The most distinctive element of the project is the series of nine inclined cylindrical columns in reinforced concrete, placed along the east façade.
Each column measures 60 cm in diameter and reaches up to 15.5 meters in height, supporting the suspended volume and transferring vertical and seismic loads to a 100 cm thick reinforced concrete foundation slab.
At the points of contact, the fifth floor slab was stiffened with 200×200 cm extradosed plinths, 90 cm thick, to counteract punching stresses from concentrated loads.

Il blocco sospeso i nove pilastri inclinati

Structural Analysis and FEM Modeling

The entire structural design was developed in full compliance with Italian Building Code (D.M. 17 January 2018) and Circular No.7/2019, through finite element modeling (FEM).
The analysis was carried out using Pro_Sap Professional 2018 by 2S.I. – Software e Servizi per l’Ingegneria, allowing for a complete simulation of the building’s behavior under static and seismic conditions.
The structure was verified under ultimate (SLU) and service (SLE) limit states, adopting a seismic behavior factor q = 1.067, classified as non-dissipative.
Linear dynamic analysis with response spectrum confirmed both the torsional deformability and overall stability of the structure, validating the effective distribution of horizontal forces through the concrete shear walls and the inclined columns.

Geotechnical Analysis and Foundation System

The geotechnical assessments were carried out on the basis of the report prepared by geologist Dr. Claudio Franzosi.

The foundation mat, with a thickness of 100 cm, was modeled at two different elevations with a level difference of 1.25 m, in order to adapt to the site’s topographic characteristics and ensure proper distribution of contact pressures.

Materials and On-Site Installation Phase

Following the completion of the reinforced concrete foundation structures, the construction phase entered its most delicate stage: the installation of the inclined columns along the east elevation of the suspended block. This was a highly complex operation from a technical standpoint, requiring the simultaneous presence of numerous specialized workers and constant coordination among site managers and technical staff, who were engaged in continuous monitoring of each lifting, alignment, and casting phase.

The columns, made of C28/35 reinforced concrete with B450C steel reinforcement and an external steel casing with a thickness of 5 mm, were installed with millimetric precision to ensure the exact design inclination and continuity with the 70 cm thick transfer slab at the top. The slabs of the upper floors complete the load-bearing system, ensuring uniform structural behavior and high performance in terms of both mechanical strength and seismic response.

During installation, continuous checks were carried out on concrete quality and geometric tolerances, confirming a construction approach focused on safety and durability. Final inspections verified full compliance with regulatory requirements and the structural stability of the inclined columns.

Balance Between Engineering and Architecture

The Busto Arsizio project stands as a tangible example of integration between structural engineering and architectural design, born from the collaboration between ENGLOBE and Ni.ma Srl, authors of the building’s concept and form.
The suspended block finds its expressive power in the inclined reinforced concrete columns wrapped in steel, which not only support the structure but also define the rhythm and identity of the façade.
Through a continuous dialogue between aesthetic intent, functional needs, and construction feasibility, ENGLOBE successfully bridged architectural vision and technical realism, ensuring coherence between the client’s expectations, structural integrity, and design quality.

Executing Contractor: Gruppo Alfano | Render Ni-Ma.it

Imprevisti di Cantiere nel Restauro del Convento di San Bernardino a Urbino
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Unforeseen Challenges on Site in the Restoration of the Convent of San Bernardino in Urbino

By Daniele Ridolfi,

Frenelli in the Restoration of the Convent of San Bernardino in Urbino

In the field of historic building restoration, unforeseen conditions are an integral part of the process. During the rehabilitation works at the Convent of San Bernardino in Urbino, one of the most significant challenges was the discovery of unexpected frenelli structures. These floor-bearing elements required innovative structural consolidation solutions and careful engineering assessments.

What Frenelli Are and Why They Represent an Unexpected Challenge

During the preliminary demolition works in the historic wing, it was revealed that the floors were supported by a series of brick frenelli.

This system, once used to connect the different levels between the old and the new convent, develops around the main cloister. The structure of the frenelli, made of bricks laid in folio, showed signs of decay and instability, worsened by the presence of two rows of “step-like” bricks placed above them.

Imprevisti di Cantiere nel Restauro del Convento di San Bernardino a Urbino

Technical Solutions for Structural Consolidation

To restore stability and ensure the usability of the building, two main strategies were adopted:

Reinforcement of Load-Bearing Vaults
The vaults, damaged by façade overturning movements, were consolidated with carbon fiber fabrics applied both to the intrados and extrados, connected with through-anchor stitching. In addition, the use of GFRP mesh was proposed to achieve global surface reinforcement.

Reconstruction of Compromised Frenelli
In areas with larger cavities, the frenelli were rebuilt and anchored to the main masonry walls using resin-bonded bars. On top of them, an OSB platform supported by wooden joists was installed, creating a solid base for the new flooring system and finishing stratigraphy.

Structural and Architectural Challenges

The unforeseen issues were not limited to the frenelli. Certain demolished areas required the reconstruction of internal partitions and the adoption of dry construction solutions in plasterboard, with curved panels designed to evoke the original vaults. This solution made it possible to preserve the historic identity while meeting the functional needs of the building.

Lessons from the Restoration of the Convent of San Bernardino

The project demonstrates the importance of a flexible and multidisciplinary approach in the restoration of protected cultural heritage assets. Structural challenges such as the discovery of frenelli require close collaboration between designers and engineers to reconcile historic preservation with the safety and functionality of the building.