Investigation Strategy for Structural Assessment of Historic Towers

Antonella Saisi,Carmelo Gentile

doi:10.3390/infrastructures5120106

Antonella Saisi, Carmelo Gentile

Open Access

https://doi.org/10.3390/infrastructures5120106

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Journal: Infrastructures	Publication Date: Dec 1, 2020
Citations: 8	License type: CC BY 4.0

Affiliation: Politecnico di Milano

Abstract

Historical masonry towers are relevant architectural heritage often in a strategic position within city centres. Their height and position require specific controls in order to define the state of preservation. The paper describes the investigation procedures developed by the authors in selected case studies. According to the timing and to the complexity of the structure, the approach requires preliminary visual inspections, geometric, crack pattern survey supplemented by historical research and stratigraphic survey. Operational modal testing evaluates the overall structural behaviour, indicating eventual local (or global) problems to study in depth by monitoring or further local tests. Emergency operations, such as controls after earthquakes, could require prompt procedures. In this case, the combination of visual inspection, geometric and damage survey with dynamic testing is a reliable procedure for structural assessment. Additional investigation increases the knowledge of local problems or gives information for further activity such as structural modelling. For instance, relevant data are the evaluation of the masonry quality or the control of the local state of stress to estimate through non-destructive or minor destructive testing in selected positions. Nevertheless, such activities require accurate projects of the investigation too, planning and localising several tests in order to solve the problems detected in the preliminary steps of the diagnosis process.

Highlights

Thinking about the country and urban skyline, towers often represent distinguishable but harmonized diffused entities in landscapes with deep historic and symbolic significances; they embody the distinctive characteristics of the construction methods of the past, mainly related to masonry
The towers—defensive, religious or civic ones—are at the same time architectonic heritage and frequently challenging structures of their time. These structures were the top of the engineering and architectural technology of their time and region, showing the builders’ deep empirical knowledge concerning the materials locally available and of the construction solutions
The first dynamic tests were time consuming, requiring forced vibration with massive devices; the evolution of the theoretic data-processing framework progressively leads toward the present estimation using operational modal analysis techniques and the acquisition of the vibration induced by the ambient excitation

Summary

Introduction

Thinking about the country and urban skyline, towers often represent distinguishable but harmonized diffused entities in landscapes with deep historic and symbolic significances; they embody the distinctive characteristics of the construction methods of the past, mainly related to masonry. Despite the frequent high quality of the past buildings, the literature documents several heavy damages during earthquakes (Figure 1) or even collapses without an evident direct action [1,2,3,4]; the analysis of such case-studies shows some common problems, including the frequent absence of a continue use and/or of controls.

Results

Conclusion