Advanced modelling for design helping of heterogeneous CLT panels in bending

International audienceCross Laminated Timber (CLT) panels are more and more common in timber construction. When submitted to out-of-plane loads, their main structural issue is the low transverse shear strength of cross layers which leads to rolling shear failure [1, 2]. The absence of specific standards yields to CLT panels having lateral boards glued each other or not, depending on the producer. The resulting discontinuities in the non-gluing case influence the global mechanical response [3]. In addition, the timber construction market requires new technical solutions for CLT. Periodic voids within the panel lead to lighter and more thermally efficient floors. However this geometry increases the panel’s heterogeneity and the difficulties in predicting the actual bending behaviour, especially the shear effects.In the first part of this work we focused our attention to a CLT layer having weak heterogeneities, namely the gaps between boards. These heterogeneities are taken into account by means of a (fictitious) equivalent and homogeneous CLT layer which mechanical properties are defined with respect to the board’s reference frame. Such an equivalent layer is combined with the exact 3D solution for laminated plates in bending [4] and a failure criterion for wood [5]. The predicted behaviour is in good agreement with a reference experimental test [6] in terms of global stiffness and variation of failure modes within the apparent elastic regime. The validated model is therefore used to investigate the influence of varying some panel’s properties on the bending response.Innovative CLT panels having periodic voids (filled by an isolating material) are already in production. An experimental campaign proved how this lay-up increases their shear weakness. The ratio wood/void can approximate the reduced elastic properties of these strongly heterogeneous panels. This approach has been already used [2] with design method for CLT in bending [7] and can be simply implemented in the Equivalent – Layer model. As a starting point we aim to compare the experimental behaviour with the predicted one using reduced mechanical properties by the ratio wood/void. These properties are combined with the model developed for weak heterogeneities and design methods for CLT in bending [7, 8].Nevertheless, such a simplified approach can’t reproduce the complexity of stresses’ and strains’ distribution, especially transverse shear ones. Therefore a more accurate model is currently in development. This solution can precisely predict the influence of high heterogeneities by means of a periodic homogenization scheme. Panel’s reduced elastic properties (EI – GA) derived with such an advanced modelling can be finally used for practical design of bending members

Comportement en flexion de panneaux en bois lamellé croisé hétérogènes

National audienceDans le domaine de la construction bois, les panneaux en bois massif lamellés croisés (CLT – Cross Laminated Timber) sont de plus en plus utilisés en tant que plancher ou toiture. Ils sont composés de plusieurs couches en bois empilées et collées de façon croisée, pour obtenir des bonnes propriétés mécaniques et hygrométriques dans les deux directions.Un enjeu technologique en développement est d’enlever du bois des planchers CLT et le remplacer avec du matériau isolant afin de rendre les panneaux plus légers et plus performants acoustiquement et thermiquement. L’utilisation de ces nouveaux planchers est encore limitée, à cause d’une connaissance insuffisante de leur comportement mécanique en flexion.Des essais de flexion 4-points sur des planchers CLT massifs et aérés ont été conduits. Cette campagne essais a montrée l’augmentation des effets de cisaillement quand le pourcentage des vides augmente. En plus, le plancher le plus aéré a montré des modes de ruine complexes liées aux effets de cisaillement roulant (RT) et traction perpendiculaire aux fibres difficiles à prévoir avec les méthodes simplifiées des ingénieurs. Ensuite, les planches en bois des planchers ont été testées pour déterminer les raideurs élastiques et les résistances. Les essais de caractérisation comprennent : traction parallèle aux fibres, compression selon les trois directions et cisaillement roulant.Une première approche pour reproduire le comportement des planchers CLT aérés peut être celui d’utiliser des méthodes pour les CLT massifs et réduire les propriétés mécanique du bois issues des essais de caractérisation par le pourcentage du vide. Les deux méthodes pour le calcul en flexion choisies sont : la méthode d’analogie du cisaillement (Kreuzinger, 1999) adoptée par la norme allemande (DIN, 2004) et un modèle développé récemment qui combine une solution analytique 3D (Pagano, 1970) avec une couche CLT homogène équivalente (Franzoni et al, 2015).Une modélisation plus avancée du comportement en flexion de ces panneaux très hétérogènes en bois est en cours. Le modèle choisi est un schéma d’homogénéisation périodique géré par une théorie de plaque pour les stratifiés (Lebée, 2012). À ce moment, seulement la raideur en flexion a été calculée avec cette méthode. Cette modélisation avancée permettra de déterminer les principaux paramètres pour concevoir ces nouveaux planchers aérés en bois, comme la raideur en flexion, la raideur en cisaillement, le chargement critique et le mode de ruine associé

Bending behaviour of massive and aerated timber floors

National audienceDans le domaine de la construction bois, les panneaux en bois massif lamellés croisés (CLT – Cross Laminated Timber) sont de plus en plus utilisés en tant que plancher ou toiture. En raison de leur facilité et rapidité de mise en œuvre et de l’orientation croisée des couches transverses qui garantit des propriétés mécaniques et hygrométriques uniformes. Une première étude [1] a identifié des hétérogénéités « faibles » affectant leur comportement en flexion et proposée une modélisation avancée pour essayer de les prendre en compte. Cette modélisation s’appuie sur un comportement homogénéisé et simplifié d’une couche en bois, une solution analytique 3D [2] et un critère de rupture pour le bois [3]. Le modèle développé a été validé sur une expérience de référence des CLT en flexion [4] en termes de raideur et modes de ruine progressifs. Ensuite, des études paramétriques ont été conduites avec le modèle validé, afin d’améliorer la connaissance sur la mécanique de ces panneaux et d’explorer aussi des configurations innovantes.Un enjeu technologique en développement est d’enlever du bois des planchers CLT et le remplacer avec du matériau isolant afin de rendre les panneaux plus légers et plus performants acoustiquement et thermiquement. L’utilisation de ces nouveaux planchers est encore limitée, à cause d’une connaissance insuffisante de leur comportement mécanique en flexion. En effet, une campagne essais de flexion 4-points a montré des ruptures complexes liées aux effets de cisaillement et difficiles à prévoir avec les méthodes simplifiées des ingénieurs. Une modélisation avancée du comportement en flexion de ces panneaux très hétérogènes en bois est en développement et les premiers résultats seront présentés. Le modèle choisi est un schéma d’homogénéisation périodique géré par une théorie de plaque pour les stratifiés [5]. Ce modèle avancé permettra de déterminer les principaux paramètres pour concevoir ces nouveaux planchers aérés en bois, comme la raideur en flexion, la raideur en cisaillement, le chargement critique et le mode de ruine associé

How skill expertise shapes the brain functional architecture: an fMRI study of visuo-spatial and motor processing in professional racing-car and naïve drivers

The present study was designed to investigate the brain functional architecture that subserves visuo-spatial and motor processing in highly skilled individuals. By using functional magnetic resonance imaging (fMRI), we measured brain activity while eleven Formula racing-car drivers and eleven ‘naïve’ volunteers performed a motor reaction and a visuo-spatial task. Tasks were set at a relatively low level of difficulty such to ensure a similar performance in the two groups and thus avoid any potential confounding effects on brain activity due to discrepancies in task execution. The brain functional organization was analyzed in terms of regional brain response, inter-regional interactions and blood oxygen level dependent (BOLD) signal variability. While performance levels were equal in the two groups, as compared to naïve drivers, professional drivers showed a smaller volume recruitment of task-related regions, stronger connections among task-related areas, and an increased information integration as reflected by a higher signal temporal variability. In conclusion, our results demonstrate that, as compared to naïve subjects, the brain functional architecture sustaining visuo-motor processing in professional racing-car drivers, trained to perform at the highest levels under extremely demanding conditions, undergoes both ‘quantitative’ and ‘qualitative’ modifications that are evident even when the brain is engaged in relatively simple, non-demanding tasks. These results provide novel evidence in favor of an increased ‘neural efficiency’ in the brain of highly skilled individuals

It’s not all in your car: functional and structural correlates of exceptional driving skills in professional racers

Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 “naïve” volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual driver's success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance

It's not all in your car: functional and structural correlates of exceptional driving skills in professional racers.

Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 "naïve" volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual driver's success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance

Psychological treatments and psychotherapies in the neurorehabilitation of pain. Evidences and recommendations from the italian consensus conference on pain in neurorehabilitation

BACKGROUND: It is increasingly recognized that treating pain is crucial for effective care within neurological rehabilitation in the setting of the neurological rehabilitation. The Italian Consensus Conference on Pain in Neurorehabilitation was constituted with the purpose identifying best practices for us in this context. Along with drug therapies and physical interventions, psychological treatments have been proven to be some of the most valuable tools that can be used within a multidisciplinary approach for fostering a reduction in pain intensity. However, there is a need to elucidate what forms of psychotherapy could be effectively matched with the specific pathologies that are typically addressed by neurorehabilitation teams. OBJECTIVES: To extensively assess the available evidence which supports the use of psychological therapies for pain reduction in neurological diseases. METHODS: A systematic review of the studies evaluating the effect of psychotherapies on pain intensity in neurological disorders was performed through an electronic search using PUBMED, EMBASE, and the Cochrane Database of Systematic Reviews. Based on the level of evidence of the included studies, recommendations were outlined separately for the different conditions. RESULTS: The literature search yielded 2352 results and the final database included 400 articles. The overall strength of the recommendations was medium/low. The different forms of psychological interventions, including Cognitive-Behavioral Therapy, cognitive or behavioral techniques, Mindfulness, hypnosis, Acceptance and Commitment Therapy (ACT), Brief Interpersonal Therapy, virtual reality interventions, various forms of biofeedback and mirror therapy were found to be effective for pain reduction in pathologies such as musculoskeletal pain, fibromyalgia, Complex Regional Pain Syndrome, Central Post-Stroke pain, Phantom Limb Pain, pain secondary to Spinal Cord Injury, multiple sclerosis and other debilitating syndromes, diabetic neuropathy, Medically Unexplained Symptoms, migraine and headache. CONCLUSIONS: Psychological interventions and psychotherapies are safe and effective treatments that can be used within an integrated approach for patients undergoing neurological rehabilitation for pain. The different interventions can be specifically selected depending on the disease being treated. A table of evidence and recommendations from the Italian Consensus Conference on Pain in Neurorehabilitation is also provided in the final part of the pape

Chromosome numbers for the Italian flora: 13

In this contribution, new chromosome data obtained on material collected in Italy are presented. It includes the first count for Dianthus carthusianorum subsp. tenorei, Helosciadium nodiflorum, Hieracium hypochoeroides subsp. cilentanum, H. lesimanum, H. scopolioides, H. terraccianoi. In addition, first Italian counts for Crupina vulgaris, Damasonium alisma, and Illecebrum verticillatum are reported

Efficacy of ketamine in refractory convulsive status epilepticus in children: A protocol for a sequential design, multicentre, randomised, controlled, open-label, non-profit trial (KETASER01)

Introduction: Status epilepticus (SE) is a lifethreatening neurological emergency. SE lasting longer than 120 min and not responding to first-line and second-line antiepileptic drugs is defined as 'refractory' (RCSE) and requires intensive care unit treatment. There is currently neither evidence nor consensus to guide either the optimal choice of therapy or treatment goals for RCSE, which is generally treated with coma induction using conventional anaesthetics (high dose midazolam, thiopental and/or propofol). Increasing evidence indicates that ketamine (KE), a strong N-methyl-D-aspartate glutamate receptor antagonist, may be effective in treating RCSE. We hypothesised that intravenous KE is more efficacious and safer than conventional anaesthetics in treating RCSE. Methods and analysis: A multicentre, randomised, controlled, open-label, non-profit, sequentially designed study will be conducted to assess the efficacy of KE compared with conventional anaesthetics in the treatment of RCSE in children. 10 Italian centres/ hospitals are involved in enrolling 57 patients aged 1 month to 18 years with RCSE. Primary outcome is the resolution of SE up to 24 hours after withdrawal of therapy and is updated for each patient treated according to the sequential method. Ethics and dissemination: The study received ethical approval from the Tuscan Paediatric Ethics Committee (12/2015). The results of this study will be published in peer-reviewed journals and presented at international conferences

Measurement of the Forward-Backward Asymmetry in the B -> K(*) mu+ mu- Decay and First Observation of the Bs -> phi mu+ mu- Decay

We reconstruct the rare decays $B^+ \to K^+\mu^+\mu^-$, $B^0 \to K^{*}(892)^0\mu^+\mu^-$, and $B^0_s \to \phi(1020)\mu^+\mu^-$ in a data sample corresponding to $4.4 {\rm fb^{-1}}$ collected in $p\bar{p}$ collisions at $\sqrt{s}=1.96 {\rm TeV}$ by the CDF II detector at the Fermilab Tevatron Collider. Using $121 \pm 16$ $B^+ \to K^+\mu^+\mu^-$ and $101 \pm 12$ $B^0 \to K^{*0}\mu^+\mu^-$ decays we report the branching ratios. In addition, we report the measurement of the differential branching ratio and the muon forward-backward asymmetry in the $B^+$ and $B^0$ decay modes, and the $K^{*0}$ longitudinal polarization in the $B^0$ decay mode with respect to the squared dimuon mass. These are consistent with the theoretical prediction from the standard model, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the $B^0_s \to \phi\mu^+\mu^- decay and measure its branching ratio${\mathcal{B}}(B^0_s \to \phi\mu^+\mu^-) = [1.44 \pm 0.33 \pm 0.46] \times 10^{-6}$using$27 \pm 6$signal events. This is currently the most rare$B^0_s$ decay observed.Comment: 7 pages, 2 figures, 3 tables. Submitted to Phys. Rev. Let