132,057 research outputs found
Introduzione
No full textSi tratta dell'introduzione alla miscellanea in onore di G. Avarucci curata dallo stesso Borri e da R. M. Borraccini
Masonry wall panels retrofitted with thermal-insulating GFRP-reinforced jacketing
No full textToday there is a need to provide thermally efficient walls, while at the same time to increase the mechanical properties of old unreinforced masonry walls that will not require large amounts of energy in the retrofitting or deconstruction processes. To address this problem, this paper gives the results of shear tests carried out on masonry panels made of solid bricks retrofitted with a new technique based on the use of glass fiber-reinforced polymers (GFRP) grids inserted into a thermal insulating jacketing. This was made of different low-strength lime-based mortars. Tests were carried out in laboratory and results were used for the determination of the shear modulus and strength of the wall panels before and after the application of the GFRP reinforcement. Retrofitted panels exhibited a significant enhancement in the lateral capacity when compared to the control panels. The thermal performance of the proposed mortars was also investigated both with and without GFRP. Low values of thermal conductivity were found, especially for the samples with GFRP; a reduction of the thermal transmittance value in the 34–45 % range was also obtained by applying 45 mm layer of coating in conventional masonry walls
Shear strengthening of wall panels through jacketing with cement mortar reinforced by GFRP grids
No full textThis paper gives the results of a series of shear tests carried out on historic wall panels reinforced with an innovative technique by means of jacketing with GFRP (Glass Fiber Reinforced Plastics) mesh inserted into an inorganic matrix. Tests were carried out in situ on panels cut from three different historic buildings in Italy: two in double-leaf rough hewn rubble stone masonry in Umbria and L'Aquila and another with solid brick masonry in Emilia. Two widely-known test methods: the diagonal compression test and the shear-compression test with existing confinement stress. The test results enabled the determination of the shear strength of the masonry before and after the application of the reinforcement. The panels strengthened with the GFRP exhibited a significant improvement in lateral load-carrying capacity of up to 1060% when compared to the control panels. A numerical study assessed the global behavior and the stress evolution in the unreinforced and strengthened panels using a finite element code
UAV trajectory control with rule-based minimum-energy reference generation
No full textThis paper deals with the hierarchical real-time control of unmanned aerial vehicles (UAVs) with rule-based strategy for mission time and energetic references generator based on optimal control theory. The objective of this work is to design a control which ensures an energy consumption close to the optimality, and easily implementable thanks to its low computational cost. The first part of the work deals with the extraction of simple and immediate rules for the determination of the optimal mission time, and the generation of 'energetic trajectories' from the analysis of the optimal control strategy results, to minimize the consumption over a high heterogeneous amount of simulations. Then, a hierarchical real-time controller is proposed to track desired energetic trajectories, identified as optimal. The results provided are validated through numerical experiments and compared in terms of energy performance with the optimal solution
Active Attitude Control of Ground Vehicles with Partially Unknown Model
No full textWe present a novel solution to the attitude control problem of ground vehicles by means of the Active Front Steering (AFS) system. The classical feedback linearization method is often used to track a reference yaw dynamics while guaranteeing vehicle stability and handling performance, but it is difficult to apply because it relies on the exact knowledge of the nonlinearities of the vehicle, in particular the tire model. In this work, the unknown nonlinearities are real-time learnt on the basis of the universal approximation property, widely used in the area of neural networks. With this approximation method, the Uniform Ultimate Boundedness (UUB) property with respect to tracking and estimation errors can be formally proven. Preliminary simulation results show good tracking capabilities when model and parameters are affected by uncertainties, also in presence of actuator saturation. Copyright (C) 2020 The Authors
Reinforcement of wood with natural fibers
No full textThis paper describes an experimental programme which examines the reinforcement in flexure of timber beams with composite materials based on natural fibers in the form of fabrics made from hemp, flax, basalt and bamboo fibers. The industrial use of natural fibers has been continuously increasing since 1990s due to their advantages in terms of production costs, pollution emissions and energy consumption for production and disposal. The technique allows the reinforcement of the intrados of beams, avoiding the dismantling of the overlying part of the structure with significant savings in terms of costs and work time. The test program consists of three phases incorporating 45 beams. The bending tests on the wooden elements made it possible to measure the increase in capacity and stiffness resulting from the composite reinforcement. This was applied to beams, creating different arrangements and using different quantities (number of layers). Despite the diversity of the various tests carried out, the results obtained in some cases showed significant increases in terms of load-carrying capacity and in deflection ductility
Decentralized Model Predictive Control of Freeway Traffic Systems over Lossy Communication Networks
No full textIn this work, we present a decentralized scheme for the control of a freeway traffic system over a non-ideal transmission channel, involving network delays ultimately resulting in possible packet losses in the digital communication. The feed-back scheme exploits the well-known Cell Transmission Model (CTM) and a ramp metering control, with actuation consisting of on-ramp traffic lights. In this context, the Model Predictive Control (MPC) approach is applied locally, in a decentralized way, which is preferable from the computational viewpoint with respect to centralized solutions, the complexity of which would grow rapidly with the dimension of the system at hand, making real-time traffic control potentially ineffective. The simulation setup is based on a traffic model whose parameters are identified using data produced by a commercial microscopic simulator of the traffic system. Preliminary performance results show the effectiveness of the approach taken, also in the case of parameter uncertainties, and look promising in view of future investigations
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