1,721,071 research outputs found
Rockfall protection of road infrastructures: design approach and numerical simulations
No full textThe protection of road infrastructure from the rockfall phenomenon is very de-manding both for design and for construction of rockfall defense works. In particular, design approach is strongly influenced by the phenomenon’s aleatory nature and the difficult determi-nation of the geomechanical parameters that characterize the interaction between the in motion rocky boulders and the affected slope ground. In this context the Authors propose a probabilis-tic methodological approach finalized to rockfall design of works through implementation of a three-dimensional simulation software called ROTOMAP®. This approach is described through the application to a case study on the road SS18 “Tirrena Inferiore” (Italy) recently affected by a drought rockfall. The results allowed verifying the effectiveness of the proposed methodology in the design process of new defensive rockfall works and in the verification of defensive exist-ing works. The reliability of the design/verification process is linked to the execution of a large number of simulations
The use of steel mesh reinforcement for the cracking control in flexible pavements: FE analysis in static and dynamic conditions
No full textThe steel mesh reinforcement of road pavements is a technology mainly used in the maintenance of flexible superstructures. Past studies have proved the benefits due to this type of reinforcing related to the reflective crack control in asphalt overlays and to the reduc-tion of shear and traction stress states in asphalt concrete. The utilization of reinforced pave-ments is largely empirical and supported by many experiences and practical applications, but there is still a knowledge gap in the modelling techniques. This paper introduces a 2D and 3D modelling approach used in order to predict and better understand the response of a steel rein-forced pavement in presence of static and dynamic actions. This was done by using a widely spreads finite elements modelling (FE) software: ANSYS®. The models were developed by as-suming a perfect elasto-plastic behaviour for the asphalt concrete and a linear-elastic behaviour for the steel reinforcement. The seismic actions were simulated by assuming the presence of a bedrock at a depth of 6m from the embankment support plane applying a maximum project ac-celeration equal to 1g. In particular, comparisons between the unreinforced and the steel rein-forced pavement were previously performed by considering static and dynamic analysis for the 2D model. In this case, the reinforcement was placed at different pavement depths evaluating its most useful position. In order to validate the modelling approach, a 3D model has been also created. Harmonic analysis has allowed to analyze the frequency response and to identify the resonance frequencies. Static and dynamic analysis have been also performed showing the dif-ferences with the 2D model. Finally, the efficacy of the reinforcement was also valuated and confirmed in presence of pavement crack. The results showed in this paper allow to confirm the effectiveness of the steel mesh reinforce technology in different conditions (2D and 3D models, with and without cracks) providing useful instructions in their design and modelling techniques
Pull-out tests on bituminous specimens with steel wire mesh reinforcements
No full textSteel reinforcements within the asphalt pavement layers have widely demonstrated to be a successful technology to avoid the propagation of bottom-up fatigue cracks.
However, the tensile stresses, induced by heavy vehicles at the bottom of bound layers, induce the crossbars unthreading compromising their proper functioning. In addition, the high temperature during laying produces dilatations of the steel reinforcement.
The main topic of this paper is the study of the asphalt layer—steel reinforcement system, analyzing the mechanical behavior and the construction materials optimization. Pull-out
tests were carried out to evaluate the effects of three different crossbars steel reinforcement in terms of pull-out resistance. The reinforcement shape and the coating materials influence the behavior of the steel wire mesh and its interaction with the asphalt mixture
Reflection based silicon incorporated silver coated fiber optic SPR sensor for refractive index and temperature measurement
Full text linkWe report a reflection based multimode fiber surface plasmon resonance (SPR) sensor utilizing a high index silicon layer between silver metal and sensing medium layer. Theoretical studies have been carried out to optimize the suitable width of material layer to sense refractive index (RI) of the analyte surrounding the optical fiber sensing region using the transfer matrix method. The RI sensitivity of the proposed SPR sensor has been experimentally verified to reach 4774 nm/RIU with figure of merit of 36.07 and resolution of 6.28E-5 at 1.38 RI. Furthermore, the large thermo-optic coefficient and thermal expansion coefficient of the silicon layer has enhanced the experimental temperature sensitivity of the SPR sensor to 1.76 nm/degrees C
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Determining the Effect of Damping Layers in Flexible Pavements on Traffic Induced Vibrations
No full textThis paper proposes a novel method to evaluating the effect of damping layers on traffic induced vibrations; it’s based on the estimation of the Rayleigh damping coefficients of different layers to be implemented in a FEM of the pavement structure. Two commonly used methods to determining those parameters are compared and then an improved approach is introduced by considering natural frequencies of the pavement structure but without underestimating damping in the basic frequency range. In addition, a more reasonable method is proposed to calculating pavement structure vibration based on shear beam model. Finally, the results of in-situ FWD tests are used to validate the accuracy of the model; the comparison between simulation and FWD results demonstrates the accuracy of the proposed method that is acceptable
Ageing effect on the relaxation properties of bitumen
No full textThe ageing of bitumen has a significant impact on the mechanical behavior of asphalt concrete. In this study, Dynamic Shear Rheometer (DSR) tests were utilized to investigate the effect of ageing on the relaxation properties of bituminous materials. PEN 70/100 bitumen films with thickness of 2 mm were exposed to laboratory ageing at various conditions. Specifically, different combinations of ageing time, temperature and pressure were applied on the bitumen films. Three evaluation indices, explicitly the shear stress at 0 s and 100 s, the ratio of shear stress at 0 s and 100 s and the time that shear stress reduces to 50% and 25% of the initial value, were used to determine the evolution of the relaxation properties of bitumen. The results show that, in comparison to fresh bitumen, aged samples show higher residual shear stresses after relaxation and are more susceptible to stress accumulation thus cracking. In addition, temperature, followed by pressure and ageing time, was found to have the stronger impact on bitumen ageing.Pavement Engineerin
Framework for replacing steel with aluminum fibers in bituminous mixes
No full textThis research explores the incentives for replacing steel fibers with aluminum fibers in fiber modified bituminous mixes. In this work the focus is on fiber modified bituminous mixes especially designed for induction heating. Inductive fibers are heated up because eddy currents are generated - according to Joule’s law - when alternating magnetic field is applied by electro-magnetic induction coil. Aluminum fiber-type particles are proposed as an alternative solution for developing corrosion resistant and lightweight bituminous mixes capable to be induced by electro-magnetic fields. In another publication (Pavlatos et al., Inductive bituminous mortar with steel and aluminum fibers, Advances in Materials and Pavement Performance Prediction, Submitted, 2018), a finite element three-dimensional model is developed in order to determine the effective electrical conductivity of steel and aluminum fiber modified bituminous mortar, as well as to show the potential utilization of alternative particles for developing multi-functional paving materials with improved properties.Pavement Engineerin
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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