The Service examines three properties in Savona, specifically two buildings (the Prefecture and Palazzina Schiadà) and a complex of 5 buildings forming the “Crespi” Barracks, headquarters of the Police Department.
The Service included the following activities:
- laser-scan survey with point cloud production;
- BIM modeling of the cloud and subsequent modeling (in REVIT) of the architectural, structural, and MEP as-built state;
- static and seismic vulnerability assessment;
- technical-economic feasibility design of structural interventions;
- BIM modeling (in REVIT) of these interventions.
The Survey
The laser-scanner survey naturally took on greater importance at the Crespi Barracks, both due to the number of buildings and the extent of the outdoor spaces.
To manage this situation, it was preferred not to create a single point cloud but to subdivide the databases, creating one that included all exteriors, including neighboring roads, and subsequently a single one for the interiors of each building.
The individual models defined by the point cloud were subsequently joined through a survey carried out with a GNSS antenna, which was used to read the coordinates of 4 pins fixed to the ground. The metric data, preliminary to the three-dimensional modeling, were acquired through the simultaneous use of two laser scanners (Leica Scan Station P40 and Leica RTC 360); approximately 300 stations were made, covering the entire surface of the buildings and the area involved.
The survey of non-visible structural and MEP parts was performed with the aid of a carbon tripod capable of carrying the instrumentation up to a height of 6 meters.
The survey activity was supported by an extensive photographic campaign and images acquired using a drone.
All acquired data were processed with Leica software: Register 360 Plus and Leica Cyclone Core (Register and Publisher Pro module) and finally exported in .rcp format for insertion into the BIM environment.
BIM Modeling
Through the BIM modeling of all acquired data, it was possible to develop architectural, structural, and MEP models. All modeling operations were carried out in compliance with the instructions contained in the Contracting Authority’s guidelines and the specifications of the Information Management Plan.
Static and Seismic Vulnerability Assessment
Structural investigations highlighted a common peculiarity among the buildings: a mixed structural configuration consisting of external infill made of unreinforced concrete and internal R.C. frames. This configuration means that under seismic actions, the internal frames, with stiffness not comparable to that of the masonry, were not “seismically engaged.”
Once the mechanical properties of the building’s structural elements were defined, the construction details investigated, and the soil classified, the analysis of the building was carried out using the FEM method, defining three-dimensional models with Sismicad 12.22 software. The seismic analysis was accompanied by a static one.
Technical-economic feasibility design of structural interventions
Considering the impossibility of suspending activities inside the buildings during the execution of the interventions aimed at static upgrading and seismic consolidation, minimally invasive consolidation interventions were planned as much as possible, compatible with the presence of occupants.
The structural interventions involved:
- significant reinforcement of the unreinforced external walls through a plating consisting of 5.00 cm of fine-aggregate concrete with standard mechanical characteristics (C25/30) and reinforcement with loose bars or welded wire mesh sized according to the height from the ground and therefore the stresses present. The plating was applied only to the external part of the masonry and in almost all the walls of the envelope, with the exception of the most stressed ones which required a bilateral solution. The intervention then involved the internal masonry orthogonal to the long sides, favoring a unilateral solution here too, where possible;
- reinforcement of the members constituting the internal frames to meet static requirements. The adopted consolidation technique specifically involved the use of high-tech materials (CFRP) limited in their extent and invasiveness, and the creation of R.C. jacketing for a small number of columns.
The proposed and implemented static consolidation interventions are indispensable and necessarily required activities inside the rooms, even if limited; the proposed anti-seismic ones are instead scalable based on the expected result. The RTP chose to achieve full compliance, determining the relative cost.
In order to provide the Contracting Authority with evaluation elements on whether or not to actually reach full compliance or stop at a 60% improvement, a reduction in interventions was planned, canceling them step by step down to the 60% threshold and, again, evaluating the cost. This operation highlighted how this downgrading led to a saving of only 20%.
