1,721,362 research outputs found
A contact-less diagnosis system for frescoes. Part two: Acoustic excitation–acoustic response
No full textThis paper presents a significantly modified technique with respect to the previous paper [L. Collini, R. Garziera, F. Mangiavacca, Development, experimental validation and tuning of a contactless technique for the health monitoring of antique frescoes. NDT&E Int 2011; 44(2):152–157], which described an NDT for the diagnosis of antique fresco paintings based on the laser measurement of the fresco’s detached areas. In this paper, we replace the laser measurement by an acoustic measurement, developing a measuring technique based on the principle “acoustic excitation—acoustic acquisition”. Replacing the laser with an acoustics has a great advantage due to the low cost of the sensors, but the drawback of its need for a more accurate and sophisticated tuning process
The effect of rotary inertia of added masses on vibrations of empty and fluid-filled circular cylindrical shells
No full textThis paper completes a study of Amabili and Garziera [2000, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part I: empty and fluid-filled shells. J. Fluids Struct. 14, 669-690; 2002a, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part II: shells containing or immersed in axial flow. J. Fluids Struct. 16, 31-51; 2002b, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part III: steady viscous effects on shells conveying fluid. J. Fluids Struct. 16, 795-809] by adding the effect of rotary inertia of added masses to the DIVA code, based on the Rayleigh-Ritz method and developed to study free vibrations of circular cylindrical shells with nonuniform boundary conditions, added masses, partial elastic bed, initial pre-stress, conveying flow or immersed in axial flow. The effect of rotary inertia has also been evaluated by commercial FEM software and experiments in order to validate the DIVA code. Calculations and experiments show that the effect of rotary inertia of added masses is generally negligible, except for additional local modes; this is in contrast with what has been found for thin plates, due to the geometric stiffness of the circular cylindrical shell
Recursive formulation for the inverse kinematics of redundant robots performing tasks with priority order.
No full text
A method for the correlation of data in modal testings of buildings
No full textThis paper deals with a method for the time and space superposition of data acquired in the dy-namical testing of large structures. The method permits two procedures comprising the integra-tion of sets of measurements taken at different times and the integration of sets of measurements taken at different places. The latter is a very useful feature when dealing with huge structures, like big buildings comprising a number of different architectural details.
The validation of this method is a case study consisting of many dynamical tests performed on an ancient castle
Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; part I: empty and fluid-filled shells
No full textNON DESTRUCTIVE EVALUATION OF AXIAL LOAD IN TIE-RODS: THE CASE OF AN ANCIENT DOME
No full textThe knowledge of the tensile load in reinforcement tie-rods is of crucial importance for the structural integrity and safety in ancient buildings. This work deals with the problem of identifying the tensile load in the tie-rods of an ancient dome in Pistoia, Italy. The proposed procedure is a non-destructive and non-invasive method. It consists in matching the first six natural frequencies of the tie-rod, acquired by a classical accelerometer, with numerically obtained frequencies. This matching procedure is accomplished by an optimization algorithm in which the length of the rod, the presence of concentrated masses along it, and an elastic foundation at the edges are the optimization variables. In this way the main unknown, i.e. the axial load, is determined by a mathematical algorithm that automatically minimizes the difference between experimental and numerical results, on the basis of the choice of multiple parameters combinations.
In particular, in this work we want to show a very interesting case study in which the method is successfully applied. An experimental campaign has been recently carried out on the Dome of Pistoia, Tuscany, see fig. 1, for the determination of the tension in the reinforcement rods. Several parameters have been considered, as the junctions, the constraints, and the presence of elastic supports. The estimation of the stress state in the tie-rods, which are from the 5th century, is carried out via a non-linear finite element analysis. Finally, considerations on the structural integrity of the rods and the safety of the buildings are drawn
Time and space superposition of dynamical testing data.
No full textThis work presents a method for the superposition in time and in space of signals acquired in the dynamical testing of large structures. The method comprises two procedures that provide the integration of sets of measurements taken at different times (time superposition) and the integration of sets of measurements taken at different places (space superposition). The latter is a very useful feature when dealing with large structures, like big buildings comprising a number of different architectural details.
The method has been tested and validated by a case study consisting of the dynamical identification performed on an ancient castle
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