On the simulation of the seismic energy transmission mechanisms

In recent years, considerable attention has been paid to research and development methods able to assess the seismic energy propagation on the territory. The seismic energy propagation is strongly related to the complexity of the source and it is affected by the attenuation and the scattering effects along the path. Thus, the effect of the earthquake is the result of a complex interaction between the signal emitted by the source and the propagation effects. The purpose of this work is to develop a methodology able to reproduce the propagation law of seismic energy, hypothesizing the "transmission" mechanisms that preside over the distribution of seismic effects on the territory, by means of a structural optimization process with a predetermined energy distribution. Briefly, the approach, based on a deterministic physical model, determines an objective correction of the detected distributions of seismic intensity on the soil, forcing the compatibility of the observed data with the physical-mechanical model. It is based on two hypotheses: (1) the earthquake at the epicentre is simulated by means of a system of distortions split into three parameters; (2) the intensity is considered coincident to the density of elastic energy. The optimal distribution of the beams stiffness is achieved, by reducing the difference between the values of intensity distribution computed on the mesh and those observed during four regional events historically reported concerning the Campania region (Italy)

The consequence of different loading rates in elasto/viscoplasticity

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Object-based audio reproduction and the audio scene description format

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The introduction of new techniques for audio reproduction such as HRTF-based technology, wave field synthesis and higher-order Ambisonics is accompanied by a paradigm shift from channel-based to object-based transmission and storage of spatial audio. Not only is the separate coding of source signal and source location more efficient considering the number of channels used for reproduction by large loudspeaker arrays, it also opens up new options for a user-controlled interactive sound field design. This article describes the need for a common exchange format for object-based audio scenes, reviews some existing formats with potential to meet some of the requirements and finally introduces a new format called Audio Scene Description Format (ASDF) and presents the SoundScape Renderer, an audio reproduction software which implements a draft version of the ASDF

Fast and Optimized Calculation of the Cable Pretension Forces in Arch Bridges With Suspended Deck

grant number 2017J4EAYBThis paper presents with an effective and fast approach to the optimization of the pretension forces in arched bridges with suspended deck, which makes use of the influence matrix method (IMM). The given cable-tensioning procedure leads to a linear system of equations with a reduced number of unknowns and can be effectively implemented within active control procedures that handle time-varying loading conditions. This method produces a target bending moment distribution (TBMD) over the structure, which significantly mitigates the state of stress of the deck. Numerical simulations referred to a Nielsen arch bridge illustrate the versatility of the proposed approach when dealing with different loading conditions.publishersversionpublishe

numerical and analytical approaches to the self equilibrium problem of class θ 1 tensegrity metamaterials

This study formulates numerical and analytical approaches to the self-equilibrium problem of novel units of tensegrity metamaterials composed of class theta=1 tensegrity prisms. The freestanding placements of the examined structures are determined for varying geometries, and it is shown that such configurations exhibit a large number of infinitesimal mechanisms. The latter can be effectively stabilized by applying self-equilibrated systems of internal forces induced by cable prestretching. The equilibrium equations of class theta=1 tensegrity prisms are studied for varying values of two aspect parameters, and local solutions to the self-equilibrium problem are determined by recourse to Newton-Raphson iterations. Such a numerical approach to the form-finding problem can be easily generalized to arbitrary tensegrity systems. An analytical approach is also proposed for the class $\theta=1$ units analyzed in the present work. The potential of such structures for development of novel mechanical metamaterials is discussed, in the light of recent findings concerned with structural lattices alternating lumped masses and tensegrity units

Theorical Models and Experimental Techniques in Nondestructive Evaluation of Concrete

When evaluating concrete strength, common opinion is that adequate precisions can be achieved only by a particular or even total destruction. However, such methods are not always applied, besides they are very laborious. The NDE methods have a number of merits, when compared with destructive ones: a possibility to find cracks and hidden flaws in concrete; besides, they show good results in testing materials of other types, such as metals and composites. At the same time, application of NDE methods to concretes is difficult because of their complex internal structure. No existing theory can predict these properties of the transmitted wave. Therefore, the main goal of the present work is to propose a theoretical model enabling the wave penetration of ultrasonic wave through a medium with multiple internal obstacles to be described adequately. Practical applications of this ultrasonic method is toward the evaluation of mechanical properties of concrete, where the influence of internal dislocations, such as pores and cracks, is of significant importance

Theorical Models and Experimental Techniques in Nondestructive Evaluation

When evaluating concrete strength, common opinion is that adequate precisions can be achieved only by a particular or even total destruction. However, such methods are not always applied, besides they are very laborious. The NDE methods have a number of merits, when compared with destructive ones: a possibility to find cracks and hidden flaws in concrete; besides, they show good results in testing materials of other types, such as metals and composites. At the same time, application of NDE methods to concretes is difficult because of their complex internal structure. No existing theory can predict these properties of the transmitted wave. Therefore, the main goal of the present work is to propose a theoretical model enabling the wave penetration of ultrasonic wave through a medium with multiple internal obstacles to be described adequately. Practical applications of this ultrasonic method is toward the evaluation of mechanical properties of concrete, where the influence of internal dislocations, such as pores and cracks, is of significant importance

Wireless and stand-alone measurement system for dynamic identification of structures

This paper contains a study about a wireless Bluetooth measurement system useful in order to control the accelerations on great dimensions structures. The structure on which they have been carried out is a steel structure with rectangular plan. On the upper level there has been installed a vibrodine for generating a sinusoidal force for dynamic characterization of the structure. The realized measurement system utilizes a datalogger and some accelerometer/ they communicate among themselves through wireless Bluetooth protocol, which allows to cover distances up to 100 m. The datalogger is a common PC equipped with a module for Bluetooth communication. The accelerometers are constituted by: 1) a triaxial acceleration sensor, with adjustable range among the following values [1.5, 2, 4, 6] g; 2) a gyroscope with input range of 150 degrees/second; 3) a microcontroller, with analogue to digital converter with maximum sampling frequency of 610 Hz, which samples the signals and manages the device; 4) a class 1 Bluetooth module which allows the communication over universal platform; 5) a 860 mAh battery. The datalogger is equipped with a software developed in Lab View environment; it is able to simultaneously acquire acceleration's samples from every accelerometer and to obtain in real time plots of accelerations, speeds and displacements and to save the samples in binary files for successive processing. The experimentation has been finalized to the calibration of the numerical model to guarantee the structure functionality and also to study the structure behaviour under dynamic actions generated by wind. This experimental activity concurred also to discover modal shape not easily recognizable also using a corrected dynamics analysis