Cracking behavior and crack width predictions of FRP strengthened RC members under tension

This paper presents and discusses the experimental results of uniaxial tensile tests of fiber reinforced polymer externally strengthened reinforced concrete (FRP strengthened RC) prisms in terms of crack width and crack spacing. As a non-contact and material independent system for in-time measurement of displacement and strain, the digital image correlation (DIC) technique has been used in this study for investigating the evolution of strains and formation of cracks during uniaxial tensile tests. As a result, the cracks were measured precisely at any load stage. The experimental results of tests performed by authors and other researchers on FRP strengthened RC members in tension are compared to prediction models from code provisions and guidelines (Eurocode 2 and fib 14), and their suitability are analyzed and discussed. The results show the dependence of the behavior and crack characteristics of FRP strengthened RC members to parameters such as wrapping scheme and FRP reinforcement ratios which are not included in design provisions for crack analysis. A new formulation for predicting crack width and spacing in FRP strengthened RC members, calibrated using the experimental results, has been proposed which considers all the main affecting parameters

On the use of case-based planning for e-learning personalization

This is the author’s version of a work that was accepted for publication in Expert Systems with Applications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Expert Systems with Applications, 60, 1-15, 2016. DOI:10.1016/j.eswa.2016.04.030In this paper we propose myPTutor, a general and effective approach which uses AI planning techniques to create fully tailored learning routes, as sequences of Learning Objects (LOs) that fit the pedagogical and students’ requirements. myPTutor has a potential applicability to support e-learning personalization by producing, and automatically solving, a planning model from (and to) e-learning standards in a vast number of real scenarios, from small to medium/large e-learning communities. Our experiments demonstrate that we can solve scenarios with large courses and a high number of students. Therefore, it is perfectly valid for schools, high schools and universities, especially if they already use Moodle, on top of which we have implemented myPTutor. It is also of practical significance for repairing unexpected discrepancies (while the students are executing their learning routes) by using a Case-Based Planning adaptation process that reduces the differences between the original and the new route, thus enhancing the learning process. © 2016 Elsevier Ltd. All rights reserved.This work has been partially funded by the Consolider AT project CSD2007-0022 INGENIO 2010 of the Spanish Ministry of Science and Innovation, the MICINN project TIN2011-27652-C03-01, the MINECO and FEDER project TIN2014-55637-C2-2-R, the Mexican National Council of Science and Technology, the Valencian Prometeo project II/2013/019 and the BW5053 research project of the Free University of Bozen-Bolzano.Garrido Tejero, A.; Morales, L.; Serina, I. (2016). On the use of case-based planning for e-learning personalization. Expert Systems with Applications. 60:1-15. https://doi.org/10.1016/j.eswa.2016.04.030S1156

Topic mining of tourist attractions based on a seasonal context aware LDA model

With the rise of personalized travel recommendation in recent years, automatic analysis and summary of the tourist attraction is of great importance in decision making for both tourists and tour operators. To this end, many probabilistic topic models have been proposed for feature extraction of tourist attraction. However, existing state-of-the-art probabilistic topic models overlook the fact that tourist attractions tend to have distinct characteristics with respect to specific seasonal context. In this article, we contribute the innovative idea of using seasonal contextual information to refine the characteristics of tourist attractions. Along this line, we first propose STLDA, a season topic model based on latent Dirichlet allocation which can capture meaningful topics corresponding to various seasonal contexts for each attraction. Then, an inference algorithm using Gibbs sampling is put forward to learn the model parameters of our proposed model. In order to verify the effectiveness of STLDA model, we present a detailed experimental study using collected real-world textual data of tourist attractions. The experimental analysis results show that the superiority of STLDA over the basic LDA model in providing a representative and comprehensive summarization related to each tourist attraction. More importantly, it has great significance for improving the level of personalized attraction recommendation

Crash Analysis of Degraded Concrete Containment Structures

Dry storage casks are composite structures made of an inner steel liner and a concrete outerpack that houses the basket of the spent nuclear fuel bundle. The concrete of dry cask structures will degrade due to the natural aging and the environmental effect shrinkage, creep, heat transfer, moisture diffusion, and Alkali-Silica Reaction (ASR). Long-term creep and shrinkage of vertical dry cask are modeled using the B4 creep formulation for concrete. The results show that creep and shrinkage does not significantly affect the performance of the dry cask structure. A fully coupled thermo-hygro-chemo-mechanical (THCM) framework is developed to consider the effect of degradation on the concrete outerpack. The coupling between heat transfer and moisture diffusion is verified through an experimental study on concrete and then implemented in the dry cask structure. Also the coupling between the chemical (in form of ASR) and the mechanical processes is verified using experimental studies on concrete cylinders. First order kinetic approach is applied to model ASR for the concrete of dry cask structure. Environmental aging is considered in the form of deleterious mismatch effects of steel and concrete deformation during the cask performance. Environmental and mechanical degradation of concrete are determined for this dry cask storage structure. A de-convolution strategy is developed to extract the material properties from the structural stiffness properties of the cask. Using this strategy, the performance of continuous surface cap material (MAT-159) model is investigated, which is available in the material library of LS-DYNA. The behaviors of the intact and aged dry cask structure and the model and prototype cask are compared in the form of stresses, strains and failure modes. The 1:3-scale model cask and the prototype cask show similar behavior by applying the added mass to the 1:3-scale model cask calculated based on the dynamic similitude theory. Also, implementing the result of mechanical and environmental degradation due to ASR to the dry cask structure, introduces widespread damages to the cask during the tip-over scenario, while the damage is still localized in case of the initial reference concrete. Two main failure modes during tip-over event are concrete crushing and shear banding.Civil and Environmental Engineering, Department o

A systematic review of scholar context-aware recommender systems

Incorporating contextual information in recommender systems is an effective approach to create more accurate and relevant recommendations. This review has been conducted to identify the contextual information and methods used for making recommendations in digital libraries as well as the way researchers understood and used relevant contextual information from the years 2001 to 2013 based on the Kitchenham systematic review methodology. The results indicated that contextual information incorporated into recommendations can be categorised into three contexts, namely users' context, document's context, and environment context. In addition, the classical approaches such as collaborative filtering were employed more than the other approaches. Researchers have understood and exploited relevant contextual information through four ways, including citation of past studies, citation of past definitions, self-definitions, and field-query researches; however, citation of the past studies has been the most popular method. This review highlights the need for more investigations on the concept of context from user viewpoint in scholarly domains. It also discusses the way a context-aware recommender system can be effectively designed and implemented in digital libraries. Additionally, a few recommendations for future investigations on scholarly recommender systems are proposed. (C) 2014 Elsevier Ltd. All rights reserved

A kinematic measurement for ductile and brittle failure of materials using digital image correlation

This paper addresses some material level test which is done on quasi-brittle and ductile materials in the laboratory. The displacement control experimental program is composed of mortar cylinders under uniaxial compression shows quasi-brittle behavior and seemingly round-section aluminum specimens under uniaxial tension represents ductile behavior. Digital Image Correlation gives full field measurement of deformation in both aluminum and mortar specimens. Likewise, calculating the relative displacement of two points located on top and bottom of virtual LVDT, which is virtually placed on the surface of the specimen, gives us the classical measure of strain. However, the deformation distribution is not uniform all over the domain of specimens mainly due to imperfect nature of experiments and measurement devices. Displacement jumps in the fracture zone of mortar specimens and strain localization in the necking area for the aluminum specimen, which are reflecting different deformation values and deformation gradients, is compared to the other regions. Since the results are inherently scattered, it is usually non-trivial to smear out the stress of material as a function of a single strain value. To overcome this uncertainty, statistical analysis could bring a meaningful way to closely look at scattered results. A large number of virtual LVDTs are placed on the surface of specimens in order to collect statistical parameters of deformation and strain. Values of mean strain, standard deviation and coeffcient of variations for each material are calculated and correlated with the failure type of the corresponding material (either brittle or ductile). The main limiters for standard deviation and coeffcient of variations for brittle and ductile failure, in pre-peak and post-peak behavior are established and presented in this paper. These limiters help us determine whether failure is brittle or ductile without determining of stress level in the material