1,720,969 research outputs found
Local and global prediction on stress-strain behavior of FRP-confined square concrete sections
No full textThe objective of this paper is to introduce a modified local-to-global methodology to understand the effect of fiber reinforced polymer (FRP) confinement on square concrete section. Traditionally, the effect of confinement on square sections has been evaluated through the so-called "arching effect" developed for steel and FRP-confined sections. FRP-confined square section was characterized by a non-uniform confinement stress field, which makes concrete strength strongly position dependent. This novel concept resulted in the "arching effect" being re-examined, which led to a methodology to evaluate the stress-strain behavior of concrete subject to arbitrary FRP confinement stress ratio at a local level. Because of the conception and realization of an innovative true-triaxial testing machine, by the first authors of this paper, research could be extended thus allowing for new test results that form the base of 1) an improved local constitutive relationship and 2) a modified approach for the evaluation of axial stress-strain behavior of an FRP confined square concrete column. The proposed approach has been validated by a set of experimental results of square columns and gave a new perspective on FRP confinement efficiency for square section
Parametric investigation on the tensile response of GFRP elements through a discrete lattice modeling approach
No full textFiber Reinforced Polymers (FRP) are a relatively new construction material. Their attractive features, such as lightness and durability, are currently paving an attractive way for structural engineering applications. However, since their mechanical properties are strongly influenced by the arrangement of the fibers (which is dictated by the production process), more research is still needed to fully characterize the material and to predict its behavior under different multi-axial actions. In this regard, the goal of the present manuscript is to shed light on these aspects by means of numerical analyses according to a lattice modeling approach proposed in (Fascetti et al., 2016) for FRP materials and herein modified to better capture the uniaxial alignment of pultruded elements. Novelty of the work and main contribution to the field is the definition of a numerical procedure for the saturation of the computational domain with different pointsets (i.e. a regular and a random one) in order to increase the accuracy of the method. The proposed approach is validated for tensile loadings, both in terms of mechanical properties and failure modes, through a parametric investigation carried out to simulate the results of the experimental campaign reported in Quadrino et al. (2018) which employed small-scale specimens directly extracted from pultruded glass fiber reinforced polymers (GFRP) beams
Design and Validation of a Fiber-Reinforced Polymer Cable-Stayed Pedestrian Bridge: Human-Induced Actions vs. Comfort Levels
Full text linkThe investigation into advanced structural materials, such as composite materials, has revealed numerous possibilities within the field of bridge engineering. Glass-fiber-reinforced polymers (GFRPs) are notable among these materials, particularly in footbridge construction, encompassing both arch and cable-stayed designs. While GFRPs boast advantages, such as their high strength-to-weight ratio, they may exhibit some deficiencies, particularly when subjected to dynamic loads induced by wind or pedestrian forces. Two noteworthy global examples are the Lleida arch bridge (Spain, 2001) and the Aberfeldy cable-stayed bridge (Scotland, 1992). These structures have recently undergone comprehensive studies by the authors to assess their behavior when subjected to specific conditions regarding pedestrian traffic and vibrations induced by under-passing trains, as far as Lleida is concerned. The methodologies employed in these studies are detailed herein, incorporating the relevant scientific literature and technical regulations that provide guidance on fundamental principles for bridge design, pedestrian modelling, and acceleration thresholds aimed at minimizing discomfort. While the framework of principles is clear, the regulations are extensive, requiring designers to have a comprehensive understanding of the diverse outcomes achievable through various approaches. Therefore, the provided state-of-the-art overview serves as a roadmap for assessing the performance of an innovative cable-stayed bridge recently proposed by one of the authors. Initially designed with six spans, this prototype has been reconfigured here as a three-span train station overpass. The analyses conducted allowed for the assessment of induced accelerations. According to current accredited standards, the resulting comfort classification is considered minimal, even if, for crowded conditions, more specific studies are required
Procedure for the statistical determination of the design FRP-confined concrete strength
No full textWorldwide research has now reached a level of integration where an effort towards the harmonization of procedures is absolutely needed. Such harmonization may regard, for example, the various steps that lead to the definition of capacity models to be included in design codes, specifically: definition of the test setup, quantities to be measured, identification of the basic variables influencing the phenomenon, distinction between average values and other fractiles, disaggregation of the model in different parts accounting for me-chanics, fine-tuning and randomnesses, and, finally, assessment of the model against the experimental results. Test results and ensuing model developed according to this procedure would naturally lend themselves to be easily shared among the scientific community and would facilitate the task of calibrating the partial coeffi-cients, with the ambitious aim of attaining a uniform reliability level among all capacity equations. This paper, based on previous author works, proposes the application of a procedure for the development of capacity design equations to the capacity model of concrete confined with FRP. The procedure has been applied, with some improving, to a new capacity model proposal and to the one included in the Italian Instructions CNR DT 200-2004. The comparison has the aim of evaluating the uncertainties of the assumed model (both of the me-chanical model and of the basic variables) to obtain a constant level of structural reliability and to outline the implication that a not very well calibrated equation could have in the definition of the characteristic value
Accuratezza di diverse procedure di pushover per l’assessment sismico su larga scala di edifici in cemento armato
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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
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