A case study of modern heritage building: Base isolation seismic retrofit for preservation of its architectural distinguishing features

Several Italian buildings designed by eminent architects and structural engineers in the second half of the 20th century are now included in modern heritage listings. At the same time, as they were designed before the issue of coordinate national Technical Standards, often require important structural rehabilitation interventions. One of the most representative case studies of that period in Florence, i.e. the building now housing the Automobile Club Headquarter and a B&B Hotel, is examined in this paper. A seismic assessment analysis carried out on the structure highlighted strength deficiencies in several members and potentially severe pounding conditions between the two constituting wings of the building, separated by a narrow technical gap. In order to improve the seismic performance without altering the architectural appearance of the building, characterized by large windows in the fa\ue7ades, free internal spaces and elegant proportions of the main structural members, a base isolation retrofit hypothesis is proposed. A substantial seismic improvement is obtained in rehabilitated conditions, as assessed by the achievement of safe stress states for all members up to the basic design normative earthquake level, as well as of maximum relative lateral displacements of the two wings constrained below the technical gap width

Enhanced Seismic Retrofit of a Reinforced Concrete Building of Architectural Interest

Modern heritage buildings designed in the 1950s and 1960s often feature poor seismic performance capacities and may require significant retrofit interventions. A representative case study in Florence, i.e., the edifice housing the Automobile Club Headquarters, is examined here. The building was designed in 1959 with an articulated reinforced concrete structure and presents some enterprising solutions for the time, including suspended floors accommodating large glazed curtain wall fa\ue7ades in the main halls. The original design documentation was collected with accurate record research and checked with detailed on-site surveys. Based on the information gained on the structural system by this preliminary investigation, a time-history assessment analysis was carried out. Remarkable strength deficiencies in most members and severe pounding conditions between the two constituting wings, which are separated by a narrow technical gap, were found. As a result, a base isolation retrofit hypothesis is proposed in order to improve the seismic response capacities of the building without altering its elegant architectural appearance, being characterized by large free internal spaces and well-balanced proportions of the main structural members. A substantial performance improvement is obtained thanks to this rehabilitation strategy, as assessed by the achievement of non-pounding response conditions and safe stress states for all members up to the maximum considered normative earthquake level. Furthermore, the very low peak inter-storey drifts evaluated in retrofitted conditions help in preventing damage to the glazed fa\ue7ades and the remaining drift-sensitive non-structural components

Can Right Ventricular Pacing be Useful in the Assessment of Cavo-tricuspid Isthumus Block?

Background: Cavo-tricuspid isthmus (CTI) block is currently assessed by coronary sinus (CS) pacing or low lateral and septal atrial pacing. Occasionally, CS catheterization through the femoral route can be difficult to perform or right atrial pacing can be problematic because of catheter instability or saturation of the atrial electrograms recorded near the catheter. Objectives: Our aim was to evaluate the feasibility of assessing cavo-tricuspid isthmus block by means of right ventricular (RV) pacing in patients with ventriculo-atrial conduction, comparing it with CS pacing.Methods: Circumannular activation was analyzed during CS and RV pacing in consecutive patients in sinus rhythm undergoing CTI ablation for typical atrial flutter. Patients without ventriculo-atrial conduction were excluded from the study. The linear lesion was created during RV pacing and split atrial signals on the ablation line were analyzed. CTI block was confirmed by analyzing local electrograms on the line of block and circumannular activation during CS and RV pacing. Results: Out of 31 patients, 20 displayed ventriculo-atrial conduction (64%) and were included in the study. Before ablation, during RV stimulation, the collision front of circumannular activation shifted counterclockwise in contrast with the pattern observed during CS pacing. After ablation, circumannular activation was similar during CS and RV pacing, showing fully descending lateral right atrium activation, even if double potentials registered on the ablation line were less widely split during RV pacing than CS pacing (111±26 ms vs 128±30 , p=0.0001).Conclusions: In patients with ventriculo-atrial conduction, tricuspid annulus activation during CS and RV pacing is similar, before and after CTI ablation. The occurrence of split atrial electrograms separated by an isoelectric interval registered on the line of block can be detected during CS or RV pacing. In patients with difficult CS catheterization via the femoral vein, before trying the subclavian or internal jugular route, if retrograde ventriculo-atrial conduction is present, RV pacing can be an easy trick to assess isthmus block

Seismic Assessment and Retrofit Design of a School Building in Florence

The recent earthquakes occurred in Italy highlighted again the high vulnerability of structures built before the release of national Seismic Standards. This induced several local authorities to undertake extensive performance assessment campaigns of public buildings, among which mainly schools. A study carried out within one of these campaigns, concerning the evaluation of seismic vulnerability and the design of retrofit interventions in a school building in Florence, is presented herein. The structure was built at the beginning of 1970s, and is characterized by a ground storey with reinforced concrete frame skeleton, and a first and second storey with steel structure. An extensive on-site experimental investigation was developed at a first step of the study, which allowed identifying the mechanical characteristics of the constituting materials, and re-drawing the main structural details. Based on these data, a check of the seismic performance in current conditions was carried out, which highlighted several drawbacks, especially concerning the steel members. This prompted to propose a seismic retrofit hypothesis of the building, consisting in the installation of a set of dissipative braces incorporating fluid viscous dampers as protective devices. A synthesis of the assessment analyses in current conditions and the retrofit design, which allows attaining an elastic structural response up to the maximum considered earthquake level, is reported in the paper

Advanced Seismic Retrofit of a Mixed R/C-Steel Structure

A study concerning the performance assessment and enhanced retrofit of public buildings originally designed without any anti-seismic provisions is presented herein. A representative structure belonging to this class was demonstratively examined, i.e., a school built in Italy in the early 1970s, before a coordinate national Seismic Standard was issued. The building is characterized by a mixed reinforced concrete (ground storey)-steel (first and second storey) frame skeleton. An extensive on-site experimental investigation was developed in the first step of the study, which helped identify the mechanical characteristics of the constituting materials, and re-draw the main structural details. Based on these data, and relevant updates of the finite element model of the structure, the seismic assessment analyses carried out in current conditions highlighted several performance deficiencies, in both the reinforced concrete and steel members. An advanced seismic retrofit hypothesis of the building was then designed, consisting of the installation of a set of dissipative braces incorporating fluid viscous dampers as protective devices. This solution makes it possible to attain an elastic structural response up to the maximum considered normative earthquake level, while at the same time causing more limited architectural intrusion and lower costs as compared to conventional rehabilitation strategies

Structural health monitoring of Artemio Franchi Stadium in Florence, Italy: measurement using interferometric radar

The \u201cArtemio Franchi\u201d Stadium in Florence, Italy, designed by Pier Luigi Nervi in 1929, was built from 1930 to 1932. The stadium has a reinforced concrete structure and it is composed by 24 stands, a 50-meter tower (\u201cMaratona\u201d tower) and a cantilever roof. In occasion of the World Cup in 1990 the stadium was renovated by adding seats at the ground level as retrofit. A study for seismic requalification is in progress and an interferometric radar has been used for monitoring the architectural complex. In particular, the radar monitored the \u201cMaratona\u201d tower and some of the stands. In this paper, the experimental results of this preliminary measurement campaign are reported. The interferometric radar is a remote sensor for monitoring large structures. When the structure under test is excited by external actions (i.e. wind, vehicular traffic, vibrodyne), the interferometric radar is able to detect the displacements of the structure and to measure its natural frequencies. The wind action was exploited to test the \u201cMaratona\u201d tower. The tower is a 30-meter tower located on a reinforced-concrete slab placed in the middle of the grandstand on the east-side of the Stadium, close to one of its well-known spiral stairs. Inside the tower an elevator is hosted. This measurement was performed both with an interferometric radar and a seismic accelerometer. The radar was installed close to an entrance of stadium, the seismic accelerometer was installed on the tower\u2019s attic. Natural frequencies were measured for these structures with both instruments, and the results were in good agreement. The stands are too rigid to be appreciably excited by wind or vehicular traffic, hence the measurements were performed during football matches. The supporters\u2019 movements were used as input action to measure the dynamic properties of stands. Unfortunately, this input was not enough wide to allow the measurement of the natural frequencies of all the stands. The experimental results of stands have been compared with a numerical model