Matteo Fratini

Dynamic Monitoring of Bridges Using a High-Speed Coherent Radar

Remote dynamic monitoring of bridges by a high-speed interferometric radar is proposed. The equipment is a continuous-wave step-frequency radar with very fast frequency hopping that is capable of sampling the structure at a rate high enough for transient analysis of motion through phase comparison of successively acquired images. An experimental test carried out on a highway bridge forced by vehicular traffic is presented

Remote Survey of the Leaning Tower of Pisa by Interferometric Sensing

The Leaning Tower of Pisa, one of the world-famous architectural marvels of Italian heritage, needs continuous surveying to assess its stability. In this letter, remote-sensing equipment recently developed by the authors, based on the principle of microwave radar interferometry, has been experimented to measure the frequency response of the Tower without requiring any contact with its structure. Wind and human traffic were used as natural excitation sources, allowing the natural frequencies of the first vibration mode of the Tower to be measured in the north-south and in the west-east directions. Modal shapes of the Tower vibrations were also obtained from data acquired by the radar.

Dynamic survey of architectural heritage by high-speed microwave interferometry

The authors propose the use of a high-speed interferometric radar for remotely measuring both transient displacements and steady-state vibrations of architectural heritage structures in order to test their stability conditions. Demonstrative results of application of the technique to a prominent cultural heritage artwork, the tower of Giotto in Florence, Italy, are reported.

ULTRA: Wideband Ground Penetrating Radar

The frequency range employed in ground penetrating radar (GPR) systems is generally limited to 2 GHz because media loss increases dramatically at higher frequencies. Nevertheless, a series of applications exists in the Cultural Heritage field where the development of high frequency systems would significantly benefit, in terms of resolution, from an increased operating band. This article presents ULTRA, a wideband GPR (800 MHz-4000 MHz) system, using a CW-SF technique developed for this type of surveying

A reconfigurable stepped frequency GPR (GPR-R)

Ground Penetrating Radars are a unique and well known tool for soil investigation.

A novel ground based multi bistatic radar for interferometric measurement of displacement vector

A novel ground based multi bistatic interferometric radar sensor has been realized in order to measure the three dimensional displacement vector of civil structures as buildings, bridges and towers.

An experimental comparison of interferometric radar vs. accelerometers for monitoring of large structures

An interferometric SFCW radar has been recently proposed as an equipment for dynamic testing/monitoring of structures like bridges, towers, buildings and so on. These operations are currently performed by networks of accelerometers. In this paper, the authors report the results of a monitoring on a steel cable-stayed footbridge and a comparison between the two measurement techniques. As the radar measures displacements and the accelerometers measure accelerations, a preliminary discussion about signals and noise is necessary.

High frequency penetrating radar data interpretation by means of joint time frequency analysis

A processing technique able to enhance the range resolution attainable through a continuous wave step frequency (CW-SF) radar on layered structures of few centimeters behind tens of centimeters masonry was tested on experimental data. The technique is based on joint time frequency analysis (JFTA). The simulated signal sweeps a finite bandwidth at discrete frequency values. The investigated medium is represented as an ensemble of four dielectric layers, homogenous and separated by flat interfaces. The transmitted wave propagates in the first semi-infinite medium, and penetrates through the second dielectric layer along the perpendicular direction. A third layer of finite thickness, and the last one supposed to be semi-infinite, follow. A laboratory experiment aimed at comparing simulated and measured results on a masonry test wall has been carried out by means of a CWSF radar system. The test-wall set up consists of a brick and lime wall at a controlled distance from a second thick masonry wall. Radar reflectivity is measured by varying the thickness of the hollow space between the two walls by means of an X band SAR system radar. The technique proved to be a promising tool for detecting stratified structure in masonry, overcoming the resolution limits of the time domain analysis.

An Interferometric CW-SF Radar for Remote Testing and Monitoring Large Structures

The authors propose to use a high speed interferometric radar equipment for static and dynamic monitoring of large structures. The equipment is a CW-SF radar with very fast hopping capability in order to sample the movements at a rate high enough to enable structural analysis to be performed. Several experimental tests have been carried out on various structures, here are presented the Cadore highway bridge (near Belluno, Italy) and the Giottos tower of S. Maria del Fiore (Cathedral of Firenze, Italy)