Papers by Giovanni Cascante
MASW Investigations on Sites with Shallow Bedrock
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2011, 2011
Solid-fluid coupling phenomena in particulate media
Laboratory investigation into the assessment of concrete pipes state of deterioration using ultrasonic testing techniques
CRC Press eBooks, Aug 26, 2020
Interparticle contact behaviour and wave propagation
Journal of Geotechnical Engineering, Oct 1, 1996
All around the world, foundation and construction codes consider the shear wave velocity (V S) pr... more All around the world, foundation and construction codes consider the shear wave velocity (V S) profile as a good indicator of soil stiffness. The definition of a V S profile is a very common practice for site classification and soil characterization in geotechnical engineering. In order to obtain the V S profile there are typically two approaches: direct exploration (e.g. Seismic Cone Penetration Test 'SCPT') and indirect exploration (e.g. seismic refraction 'SR' and multichannel analysis of surface waves 'MASW' techniques). Both, direct and indirect techniques require the use of an energy source to generate the waves necessary to characterize the V S soil profile; for near surface (depth less than 30m) usually an impact force is used as input source. The shear wave velocity (Vs) is equal to the product of wave length () and wave frequency (f). On one side, wave length represents the limitation in terms of vertical resolution for indirect techniques; the shorter the wave length, the better the vertical resolution (thinner layers can be detected). On the other side, frequency content for the input source is not very well studied and its effect on vertical resolution for the Vs profile is not very well understood. As the Vs depends only on the soils variability, there is no way to modify it in the tests; so, what is modifiable in during the test is the frequency content in the input source and as a collateral effect, the wave length.
Among the different typologies characterizing historic masonry structures, those witch present th... more Among the different typologies characterizing historic masonry structures, those witch present the most unknown physical and mechanical properties of their internal components, are the structures shaped by massive masonry. The reference is made to examples like the lower part of bell towers, high ditch walls of citadels, retaining walls of rivers or canals, as well as spandrels and piers of arch bridges. How to know the effective structural and load bearing hidden thickness as well as the internal grade of integrity of the wall or pier is still at present a debating issue. Among the wide variety of sonic methods used for detection of internal discontinuities, the Spectral Analysis of Surface Waves (SASW) was developed since decades ago, with different applications, mainly in geothecnical area and reinforced concrete structures, both in the time domain and the frequency domain. In the case of massive masonry elements, techniques analyzing and processing the data with models using phase velocity, frequency-wave number and power spectral analysis seem to present high reliability of detecting the material discontinuities, even of small dimension. Recalling the actual background of sonic non-destructive test different applications, t he paper describes the calibration procedure used and the techniques implemented, in term of technological in-situ application and data processing, for the investigation of a retaining masonry wall of an historic water canal near the masonry abutments of a bridge, interested by heavy traffic downtown Milan.
Novel application of wavelet synchrosqueezed transform (WSST) in laser-vibrometer measurements for condition assessment of cementitious materials
NDT & E international, Jun 1, 2021
Abstract Early damage detection is of interest in the non-destructive testing of civil infrastruc... more Abstract Early damage detection is of interest in the non-destructive testing of civil infrastructure. Traditional wave velocity-based methods are not sufficient as they use only one data point of information, neglecting the frequency content of ultrasonic signals. This paper demonstrates the advantages of applying the wavelet synchrosqueezed transform (WSST) to include the wave attenuation approach for condition assessment of cementitious materials. The application of the WSST is presented in three steps. First, synthetic models are studied to demonstrate the capabilities and limitations of the WSST technique, focusing on the ultrasonic frequency range. Next, the WSST is used to extract the main vibration modes to characterize ultrasonic transducers using a state-of-the-art laser vibrometer. Finally, a new WSST-based attenuation analysis technique is used for the evaluation of localized damage in a cemented sand specimen. Our results show that the WSST technique can be used to detect damage using ultrasonic measurements as long as the main frequency components are well separated. The characterization of ultrasonic transducers using WSST gives a better understanding of the frequency content of transmitted signals, which are generated not only by the resonance of piezoelectric crystal but also by the resonance of the surface-wearing plate of the transducer itself. The application sections of the paper show that the proposed approach can be successfully used for early damage detection in the case of localized damage. The WSST-based technique can improve the sensitivity of attenuation analysis in the detection of localized damage up-to 36%.
Multi Geometry Approach for MASW Survey‐Field and Synthetic Data Results
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2011, 2011
Novel evaluation of mass polar moment of inertia of the drive plate in resonant column
Geotechnique Letters, Sep 1, 2022
Resonant column (RC) is a standard laboratory test for the dynamic characterization of soils. Mas... more Resonant column (RC) is a standard laboratory test for the dynamic characterization of soils. Mass polar moment of inertia (MPMI) of the drive plate of RC is required for the solution of equation of motion for a specimen-mass system in RC. In standard procedure, the MPMI is evaluated by testing of calibration probes. Studies have shown that torsional stiffness of the probes have significant effect on the evaluation of MPMI of drive plate due to contribution from base of RC. The extent of contribution increases with increase in torsional stiffness of probes and consequently error in MPMI increases. This study presents a new calibration method that does not use probes. The MPMI of the drive plate is evaluated by suspension of drive plate with polyamide wire of negligible torsional stiffness and damping. The modified equation of motion is used to evaluate the MPMI of drive plate. Results show that the variation of MPMI with frequency is very small compared to its variation from conventional procedure. The apparent values of MPMI from conventional procedure are found to be higher than its inferred true-value, which results in overestimation of shear wave velocity of soil specimen.
Probabilistic evaluation of changes in dynamic properties of structures
HAL (Le Centre pour la Communication Scientifique Directe), Sep 26, 2021
Condition Assessment of Concrete Beam Using a Laser Vibrometer
The bender element (BE) test has been widely used for the dynamic characterization of soil specim... more The bender element (BE) test has been widely used for the dynamic characterization of soil specimens at low-shear strain levels. However, the actual behavior of the BE inside a soil specimen remains unknown. Thus, the current ASTM standard does not consider the interference of compressional and shear waves in BE testing, which can lead to significant errors in the evaluation of shear wave velocities. The main objective of this paper is to present a numerical model of the BE system to better understand the response of the BEs inside a soil sample. The model is calibrated, verified, and then used to demonstrate the importance of taking into consideration the interaction between compressional and shear waves for the correct interpretation of BE measurements. The model successfully captured the measured vibrations of the BE in air as well as inside transparent soils. More importantly, the numerical simulations provide a new understating of the significant interactions of P-waves and S-waves especially in clay soils. Thus, the proposed coupled piezoelectric and solid mechanics model can be used to study the soil-BE interaction so that sound recommendations can be given to improve the interpretation of BE tests in different soils.
<b>Detecting Defects in Steel Reinforcement Using the Passive Magnetic Inspection Method</b>
Journal of Environmental and Engineering Geophysics, Jun 1, 2017
Defects in steel reinforcement are critical factors in the evaluation of the service life of rein... more Defects in steel reinforcement are critical factors in the evaluation of the service life of reinforced concrete (RC). Steel reinforcement (bar) defects or deterioration may lead to crack propagation and strength decrease in RC structural members. Deterioration also changes the steel magnetic properties; the evaluation of these changes can be investigated by an indirect passive and non-invasive method to locate and quantify defect in RC structures. Herein, a passive magnetic inspection (PMI) method is modified and used to examine its potential as a non-destructive testing (NDT) method for condition assessment of steel reinforcement. The passive magnetic flux density of steel bar with three small holes in three different positions and locations along the bar is measured in the laboratory. A signal processing methodology based on frequency spectrum analysis and filtering is applied to the experimental data, and the results are compared with the numerical simulation. The processed data from the experimental test shows the potential of PMI method to detect, locate and evaluate bar condition. Both experimental results (after signal processing) and simulation results show a good similarity for top and bottom holes. Cross-correlation of numerical simulation with experimental data was necessary to reveal detection of the side hole.
Applied sciences, Sep 2, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Mathematically Enhanced Corrosion Detection
Mathematics in Computational Science and Engineering
Géotechnique, 2019
Bender elements (BEs) are commonly used by geotechnical laboratories worldwide to measure the she... more Bender elements (BEs) are commonly used by geotechnical laboratories worldwide to measure the shear-wave velocity of soils. However, the actual behaviour of BEs inside the soil specimen has never been directly measured. There is experimental, numerical and analytical evidence that the shape and frequency content of the actual transmitter movement are different from the shape and frequency content of the input voltage signal, although this disparity has never been validated for BEs placed inside a soil specimen. In order to systematically investigate the disparity between the input signal and the actual transmitter response and to advance the understanding of the frequency response of the transmitter inside the soil, an experimental programme is designed to measure, for the first time, the responses of BEs placed inside soil specimens. To capture the transmitter response when placed inside the soil, a transparent granular soil is used to allow penetration of a laser beam from a laser...
Characterization of Ultrasonic Transducer Response Using Laser Doppler Interferometer in kHz-Range for Civil Engineering Applications
Journal of Nondestructive Evaluation, Jul 1, 2022
Wood poles are widely used to support overhead distribution and transmission power lines in North... more Wood poles are widely used to support overhead distribution and transmission power lines in North America and the world. These poles are vulnerable to internal deterioration due to extreme weather conditions, requiring a large number of poles to be inspected every year. This paper presents a comparative study of four stress wave-based nondestructive testing (NDT) methods commonly used for condition assessment of wood poles. These include the traditional approaches of sounding, sonic pulse velocity, and ultrasonic pulse velocity tests; and a new approach that considers the orthotropic characteristics of wood, uncertainties in the elastic properties, ultrasonic wave velocity and attenuation. Two poles with an internal hole of 4% of the cross-section are evaluated and compared by each method. Ultrasonic measurements of wave velocity and attenuation considering orthotropic characteristics of wood and uncertainties in the elastic properties provide a reliable wave-based NDT method for the detection of early decay in wood poles.
Report, 2017
Ultrasonic Pulse Velocity (UPV) method is a very popular technique used in Non-Destructive Testin... more Ultrasonic Pulse Velocity (UPV) method is a very popular technique used in Non-Destructive Testing (NDT) in Civil Engineering. Major benefit of the method is its simplicity. UPV uses the concept of measuring time of a first arrival of ultrasonic wave from one side of the specimen to another. Moreover, UPV is an ASTM standard test method for concrete specimens. In spite of an easiness of the method obtained results highly depend on the transducers used, coupling quality, and specimen dimensions. In the article the authors focus on the sensor and specimen effects. The results for UPV tests of 9 concrete specimens of different heights and diameters are presented. The specimens are tested with 54 kHz and 850 kHz excitation transducers and the state-of-the-art laser vibrometer (response measurements). This study discusses the laser vibrometer readings and the influence of specimen dimensions (with the dominating factor of length effects in terms of wavelength and specimen length relation) on the measured pulse velocities. Practical recommendations for the minimal dimensions of the test object in order to minimize the error in UPV tests are proposed.
Geotechnical Testing Journal, Jul 19, 2019
Nondestructive acoustic testing is used to assess damage in infrastructure as a function of elast... more Nondestructive acoustic testing is used to assess damage in infrastructure as a function of elastic wave velocity and attenuation variations. This study focuses on understanding the effects of a thin fracture on ultrasonic elastic wave velocity and attenuation. Experiments were performed on the effects of a thin interface fracture within polymethylmethacrylate (PMMA) specimens. Wave velocity and attenuation were measured across the width of the homogeneous specimen using the ultrasonic pulse velocity (UPV) method. Seventeen specimens (12.5 mm and 25.4 mm thick) were tested under three conditions. First, the intact annealed interface between two PMMA blocks was tested; then, specimens with a small hole perpendicular to the interface and milled ends were tested; and finally specimens with the center hole and an induced fracture at the annealed interface were tested. Four extra specimens, two with annealed (but weak) interfaces between blocks and two solid blocks, were tested during the fracture growth process under uniaxial straincontrolled test conditions. Wave velocity results show a marginal reduction up to 4% when damage in the form of a thin fracture is present; whereas there is a reduction of up to 60% in attenuation readings. The findings confirmed the reliability of using wave attenuation to identify the presence of thin fractures with the UPV condition assessment method in a homogenous medium.
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Papers by Giovanni Cascante