Structural consolidation of listed historical and monumental assets

XX / 07/2021 – It historical building heritage Italian is extraordinary but, at the same time, in need of special care; this requires a constant commitment to the development of solutions increasingly effective and compatible.

The evolution of sensitivities regarding the recovery of historical-architectural assets has therefore imposed new reflections concerning, not only the construction materials and those related to the energy efficiency of buildings, but also technologies for the structural consolidation.

For such systems today we no longer question only about efficacy and durability, but also those aspects related to compatibility with the works subject to intervention and the principles of sustainability.

Structural reinforcement technologies they can be perfectly compatible with historical assets? They are able to respond to the protection needs of the same provided for by the superintendencies?

Also, the same materials can meet for example the minimum environmental criteria (CAM) and therefore be counted among the ‘environmentally preferable’ products and be adequate to the requirements of the public administration?

These questions were the subject of an interesting comparison that took place with Federico Picuti, Kimia Communications Manager, and Ph.D. Ing. Stefano Agnetti, Kimia Technical Department Manager, who told us: “the answers to these questions are not so obvious and for many reasons they are still to be written. However, there are some exemplary cases that allow us to be already very optimistic and to look at future developments with particular interest. “

Federico Picuti and Stefano Agnetti then shared, in a two-part story, a exemplary case study: the restoration, seismic adaptation and energy requalification of the stables of the Rocca di Sant’Apollinare, the first historic building in the world to obtain the GBC Historic Building certificate, protocol created by GBC Italia and developed on the basis of the certification scheme LEED®.

The Rocca di Sant’Apollinare: an exemplary case of sustainable recovery

The recovery project of the Rocca di Sant’Apollinare, an ancient Benedictine abbey of the 10th century, located in Spina di Marsciano, in the province of Perugia, was commissioned by the Foundation for Agricultural Education of the Umbrian capital and had as scientific director Prof. Franco Cotana, full professor of Industrial Technical Physics at the Engineering Department ofUniversity of Perugia.

The intervention, now recognized as a a unique example of redevelopment in the world, is the result of the collaboration between the University of Perugia and a group of companies chosen for their experience in the field of recovery interventions, from static consolidation and of energy efficiency of historic buildings.

State of the building prior to the intervention © Kimia

The stables of the Rocca di Sant’Apollinare have obtained the level of “GOLD” certification, with 72 points out of 110. The score derives from the requirements set by the GBC protocol which requires, in view of a philosophy aimed at energy efficiency and the reduction of the environmental impact of the existing, compliance with a series of specific rules, such as, for example, in the case of the Rocca, finding the materials to be used on site and the use of integrated automation solutions for home automation.

The structural consolidation intervention

the restoration and redevelopment works of the building have been many and range from the reuse of some raw materials such as terracotta tiles, wooden beams and tiles, to the execution of structural interventions on the walls and vaults, from the reconstruction of the wooden roof, to the aspects of energy efficiency with the execution of radiant floors and a cork thermal insulation system.

For what concern structural consolidation the design choice fell on Kimia solutions. This choice was affected by the origin of the company, which is based in Perugia, the possibility of using products of recognized quality and, in particular, the possibility of using a highly compatible structural reinforcement technology with the wall structures of the building: the composite system Kimisteel INOX, a FRCM (Fiber Reinforced Cementitious Matrix) type system. Solution used specifically for the making the hoop at the level of the first floor of the building, for the making chains positioned on the extrados of the floor e for the reinforcement of the barrel vault.

“Quincunx” consolidation injections

As far as the walls of the building are concerned, first of all, some consolidation injections with fluid grout based on natural hydraulic lime Limepor 100 and fiber-reinforced mortar was also applied stucco M15 for the rough coat and for the realization of the plasters.

The low pressure mortar injections were carried out according to technique a “staggered”, that is, by drilling the walls according to a pattern that recalls the representation of the number five on the face of a die. This practice allows the injected mortar to flow more evenly, thus avoiding the formation of empty spaces inside the masonry.

Structural consolidation of listed historical and monumental assets Injection scheme of the “quincunx” masonry © Kimia

The reinforcement of the barrel vaults

For the barrel vault in brick the need for reinforcement went hand in hand with that of not increasing the weight on the vaulted elements.

In this sense, the stainless steel system was very effective as, in addition to having high mechanical resistance characteristics within the lime matrix, it proved to be extremely light and low invasive.

The reinforcement project of the barrel vault, located on the ground floor of the building, at the main access to the former stables, provided for the creation of a mesh of stainless steel bands arranged in a curvilinear direction according to the direction of the vault and in a longitudinal direction according to the generatrix.

Structural consolidation of listed historical and monumental assets Consolidation of the barrel vaults with the stainless steel kimisteel system © Kimia

At the ends, in correspondence with the graft of the arch on the walls, instead of perforations in the wall thickness in which the bands of stainless steel fabric have been inserted, rolled up in the form of urbanization.

In this way, the reinforcement system positioned on the extrados of the vault performs the function of connection between the two opposite walls. This fixing system also had the function of avoiding the possible detachment of the ends of the composite.

The intervention of floor hooping

The same connection function of the walls was obtained by making a bandage with Kimisteel INOX at the level of the first floor from the outside and, at the same time, by placing bands on the extrados of the structural slab of the floor.

Structural consolidation of listed historical and monumental assets Positioning of stainless steel bands on the floor to connect the walls © Kimia

the bands positioned on the floor were then superimposed on the external bandage and frayed always externally. These bands, after having crossed the extradosal surface of the floor, crossed the masonry after rolling up the fabric and inserting it into the perforations, specially made at the level of the floor. Finally, they too have been sfioccate.

Structural consolidation of listed historical and monumental assets External flaking of the fabric in stainless steel © Kimia

A box-like system of the building was obtained with a further connection of the opposite walls, exploiting the stainless steel bands like real tie-rods.

Unlike common steel tie rods, the use of stainless steel makes it possible to exploit a reinforcement system corrosion free. The stainless steel of the reinforcement fabric, in fact, is able to remain in contact with the humidity present inside the walls without rusting and, consequently, without the occurrence of injuries, detachments and cracks due to the increase in volume. .

The application phases of the FRCM system

In order for the FRCM Kimisteel INOX system to correctly perform its reinforcement function, the support preparation phases are essential. Having to ensure optimal adhesion to the substrate, before its application, it is necessary to remove the various layers that cover the substrate or plasters, smoothing compounds and paints.

For the extrados reinforcement of the building vaults, the existing flooring, the screed and the underlying filling were removed. Particular attention was paid to maintaining the flatness of the wall surface, on which it is always advisable to create regularization tracks with lime-based mortars.

Furthermore, where the support had modest mechanical characteristics and in the presence of superficial dustiness, the use of the Kimia technicians was suggested adhesion promoter epoxy, two-component, water-based, Kimicover FIX, used before applying the stainless steel bands to the vaults.

Structural consolidation of listed historical and monumental assets Insertion of the stainless steel fabric in the lime matrix © Kimia

The operations for applying the FRCM system included, in order, the following phases:
1) application of the first layer of mortar on the surface;
2) inserting the stainless steel fabric;
3) light pressure of the fabric itself inside the inorganic matrix to make sure that all the strands were completely drowned;
4) application of the second layer of lime mortar to cover the strip.

This standard procedure made it possible to obtain a “package” in which i filaments of the steel fabric are stressed in a uniform and homogeneous way. In fact, the lime mortar offers the ability to redistribute the stresses between the various strands, preventing them from sliding.

The Rocca di Sant’Apollinare today

The Rocca di Sant’Apollinare currently houses the offices and laboratories of the Biomass Research Center of the University of Perugia. In the former convent dryers, a team of experts and researchers produces vegetable oil starting from local soybean, sunflower, rapeseed and thistle crops. The oil powers a trigeneration system that supplies energy to the entire building. Similarly, all discharges and wastes are used to produce biogas and natural fertilizers, with the aim of verifying the effective potential of the circular economy.

The project of restoration, consolidation and energy requalification of the Rocca for its part, in addition to the primacy for obtaining the certification GBC Historic Building and to a great international resonance, he was also awarded the “Sustainable Development Award 2016 – Green Building Sector“, promoted by the Foundation for Sustainable Development and by Ecomondo – Rimini Fiera, with the patronage of the Ministry of the Environment.

Source: Le ultime news dal mondo dell'edilizia by

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