Micelli F.,University of Salento |
Modarelli R.,CETMA Consortium
Composites Part B: Engineering | Year: 2013
The use of fibre reinforced polymer (FRP) composites has been successfully promoted and experienced for external confinement of reinforced concrete (RC) columns and pillars all over the world. Increase in compressive strength and energy absorption before collapse have been largely experienced in laboratory environment during the last decade, mostly by testing concrete cylinders wrapped with FRP jackets. In this study the results of a large test program are presented with the objective of examining the effect of various experimental parameters on the confinement effectiveness of FRP jackets on both circular and rectangular concrete columns with solid or hollow core. The experimental parameters include: different concrete strength, type of fibres, number of wrap layers, geometry of the column, corners radius, full/hollow core and cross-sectional aspect ratio (only for prismatic elements). FRP-confined and unconfined specimens have been loaded in uniaxial compression until failure. Totally 128 specimens were prepared and tested, 89 of them were strengthened with Carbon FRP (CFRP) and Glass FRP (GFRP), the remaining 39 were tested as plain concrete reference. Compressive stress, axial and hoop strains have been measured to evaluate the stress-strain relationships, ultimate strength, stiffness, and ductility of the specimens. Results confirmed that external confinement produced by FRP can significantly enhance compressive strength, ductility and energy absorption capacity if compared to those of plain concrete. The effects of test parameters are evidenced and compared in order to show the sensitiveness of the mechanical problem for each of them. Important design information are furnished to researchers and practitioners also by comparing the results of the experimental campaign with the prediction of different analytical models, based on well-known and widely accepted mechanical assumptions. Design equation recommended by CNR (Italian National Research Council) were also applied by assuming unitary values for safety factors, in order to see the reliability of the mechanical model proposed by CNR. © 2012 Elsevier Ltd. All rights reserved.
Blanco J.L.,University of Almeria |
Bellone M.,CETMA Consortium |
Gimenez-Fernandez A.,University of Almeria
International Journal of Advanced Robotic Systems | Year: 2015
The autonomous navigation of vehicles typically combines two kinds of methods: a path is first planned, and then the robot is driven by a local obstacle-avoidance controller. The present work, which focuses on path planning, proposes an extension to the well-known rapidly-exploring random tree (RRT) algorithm to allow its integration with a trajectory parameter-space (TP-space) as an efficient method to detect collision-free, kinematically-feasible paths for arbitrarily-shaped vehicles. In contrast to original RRT, this proposal generates navigation trees, with poses as nodes, whose edges are all kinematically-feasible paths, suitable to being accurately followed by vehicles driven by pure reactive algorithms. Initial experiments demonstrate the suitability of the method with an Ackermann-steering vehicle model whose severe kinematic constraints cannot be obviated. An important result that sets this work apart from previous research is the finding that employing several families of potential trajectories to expand the tree, which can be done efficiently under the TP-space formalism, improves the optimality of the planned trajectories. A reference C++ implementation has been released as opensource. © 2015 The Author(s).
Modarelli R.,CETMA Consortium
COST ACTION C26: Urban Habitat Constructions under Catastrophic Events - Proceedings of the Final Conference | Year: 2010
Past studies demonstrated the structural efficiency of FRP-confinement for reinforced concrete (RC) columns to increase their strength and ductility in axial compression. Numerical and analytical modelswere developed to predict the stress-strain behavior of FRP confined concrete and recommendations were provided to practitioners for design of FRP-retrofitted RC columns. Scientific studies related to FRP-confinement of hollowcore RC columns are very limited at the moment. This clashes with the thousands of applications all over the world in which bridge piers are designed as hollow-core columns to maximize the structural efficiency in terms of strength/mass and stiffness/mass ratios. In previous works the author carried out a large experimental program on both solid and hollow-core concrete prisms and cylinders. In this framework several specimens were tested under uniaxial compression to study the influence of various experimental parameters on the effectiveness of FRP jackets applied to concrete columns subjected to uniaxial compression loading. In this work, on the basis of the experimental results obtained, an analytical model has been developed and calibrated for predicting the confined ultimate strength of both solid and hollow-core FRP-confined concrete members. The performance of the model has been then compared with that of the most known models, previously developed for FRP confinement of concrete element, on a wide set of experimental data available in literature obtaining good results. © 2010 Taylor & Francis Group, London.
Greco A.,University of Salento |
Frigione M.,University of Salento |
Maffezzoli A.,University of Salento |
Marseglia A.,CETMA Consortium |
Passaro A.,CETMA Consortium
Materials | Year: 2014
This work is aimed to present an innovative technology for the reinforcement of beams for urban furniture, produced by in-mold extrusion of plastics from solid urban waste. This material, which is usually referred to as "recycled plastic lumber", is characterized by very poor mechanical properties, which results in high deflections under flexural loads, particularly under creep conditions. The Prowaste project, founded by the EACI (European Agency for Competitiveness and Innovation) in the framework of the Eco-Innovation measure, was finalized to develop an innovative technology for selective reinforcement of recycled plastic lumber. Selective reinforcement was carried out by the addition of pultruded glass rods in specific positions with respect to the cross section of the beam, which allowed optimizing the reinforcing efficiency. The reinforcement of the plastic lumber beams with pultruded rods was tested at industrial scale plant, at Solteco SL (Alfaro, Spain). The beams obtained, characterized by low cost and weight, were commercialized by the Spanish company. The present paper presents the most relevant results of the Prowaste project. Initially, an evaluation of the different materials candidates for the reinforcement of recycled plastic lumber is presented. Plastic lumber beams produced in the industrial plant were characterized in terms of flexural properties. The results obtained are interpreted by means of beam theory, which allows for extrapolation of the characteristic features of beams produced by different reinforcing elements. Finally, a theoretical comparison with other approaches which can be used for the reinforcement ofplastic lumber is presented, highlighting that, among others, the Prowaste concept maximizes the stiffening efficiency, allowing to significantly reduce the weight of the components. © 2014 by the authors; licensee MDPI, Basel, Switzerland.
Micelli F.,University of Salento |
Angiuli R.,CETMA Consortium |
Corvaglia P.,CETMA Consortium |
Aiello M.A.,University of Salento
Composites Part B: Engineering | Year: 2014
Fiber Reinforced Polymer (FRP) composites are widely used for strengthening and conservation of historic masonry, even if research problems are still open. The mechanical behavior of masonry columns having a circular cross section, confined with glass and basalt FRP systems was studied in this paper. An extended experimental investigation is presented in order to show the results of axial compression tests on circular masonry columns built with natural blocks (calcareous stone). Active confinement was also studied by using a novel technique that employs Shape Memory Alloys (SMA). Totally twenty-four masonry columns were built, instrumented and tested. Different fibers, strengthening schemes and matrix/adhesive were used for the confinement of the columns. Unstrengthened columns were tested as reference specimens. Axial strain of the columns and tensile strain of the fibers in the direction perpendicular to the primary axis of the columns were measured with the applied load. Experimental results revealed the effectiveness of the FRP-confinement for masonry columns. Active confinement was found to be effective at early loading stages since an increased stiffness of the SMA/GFRP-confined columns was measured. A prediction of the compressive strength was obtained by using the model of the Italian guidelines CNR DT 200 (National Research Council) in order to compare the experimental results with the design approach, also for new types of fiber like basalt which were not included in the technical codes. Finally, the experimental results were compared with theoretical values calculated according with to two existing analytical models in order to test their effectiveness for the analyzed configurations. © 2014 Elsevier Ltd. All rights reserved.