Étude de l'effet de la rotation des brides sur la fuite des assemblages boulonnés munis de joints d'étanchéité

Revue bibliographique et approche du code -- Approche du code ASME -- Méthode traditionnelle -- Méthode nouvelle de calcul -- Protocole d'essais -- Le montage expérimental -- Méthodologie de mesure de fuite -- Condition d'essai et nombre de tests -- Validation et analyse des résultats -- Comparaison de la fuite entre différents types de joint -- Étude par éléments finis -- Définition du modèle d'éléments finis -- Distribution de la contrainte de contact du joint -- Rotation de la bride et vérification du modèle d'éléments finis -- Rotation de la face surélevée de la bride -- Distribution radiale de la contrainte de compression sur le joint -- Écrasement du joint -- Influence de la rotation de la bride sur la fuite -- Performance des modes de calcul -- Calcul de la largeur effective des joints

Separation gap, a critical factor in earthquake induced pounding between adjacent buildings

In this paper it is attempted to study seismic responses of adjacent buildings subjected to earthquake induced pounding and to clarify pounding effects for various separation gaps. An analytical model of adjacent buildings resting on a half-space is provided whilst the buildings are connected by visco-elastic contact force model. Results show that with same separation gap, adjacent buildings with structure-soil-structure interaction (SSSI) are more likely to pound together than buildings with fixed-based (FB) condition. Also, building condition gets worse due to pounding because the seismic responses of buildings are unfavourably increased and the condition becomes more critical if the separation gap becomes narrower

Present and future of gait assessment in clinical practice: Towards the application of novel trends and technologies

BackgroundDespite being available for more than three decades, quantitative gait analysis remains largely associated with research institutions and not well leveraged in clinical settings. This is mostly due to the high cost/cumbersome equipment and complex protocols and data management/analysis associated with traditional gait labs, as well as the diverse training/experience and preference of clinical teams. Observational gait and qualitative scales continue to be predominantly used in clinics despite evidence of less efficacy of quantifying gait.Research objectiveThis study provides a scoping review of the status of clinical gait assessment, including shedding light on common gait pathologies, clinical parameters, indices, and scales. We also highlight novel state-of-the-art gait characterization and analysis approaches and the integration of commercially available wearable tools and technology and AI-driven computational platforms.MethodsA comprehensive literature search was conducted within PubMed, Web of Science, Medline, and ScienceDirect for all articles published until December 2021 using a set of keywords, including normal and pathological gait, gait parameters, gait assessment, gait analysis, wearable systems, inertial measurement units, accelerometer, gyroscope, magnetometer, insole sensors, electromyography sensors. Original articles that met the selection criteria were included.Results and significanceClinical gait analysis remains highly observational and is hence subjective and largely influenced by the observer's background and experience. Quantitative Instrumented gait analysis (IGA) has the capability of providing clinicians with accurate and reliable gait data for diagnosis and monitoring but is limited in clinical applicability mainly due to logistics. Rapidly emerging smart wearable technology, multi-modality, and sensor fusion approaches, as well as AI-driven computational platforms are increasingly commanding greater attention in gait assessment. These tools promise a paradigm shift in the quantification of gait in the clinic and beyond. On the other hand, standardization of clinical protocols and ensuring their feasibility to map the complex features of human gait and represent them meaningfully remain critical challenges

Influence of mesh density on a finite element model’s response under dynamic loading

This paper investigates the influence of mesh density of two-dimensional and threedimensional finite element models (FE) on elastic wave propagation. These models with their elastic material properties were generated using different mesh sizes and were subjected to a dynamic sinusoidal vibration, in order to investigate the mesh density dependence of a FE model under dynamic loading, such as in crash biomechanics where propagating waves are generated in biological soft tissues. Responses in terms of wave propagation, shear stress and longitudinal displacement and velocity induced by propagation of the elastic waves were studied. Results showed that mesh size has a great influence on the propagation of shear waves and on the maximum shear stress. The need for a specific mesh size, depending on shear wavelength, to ensure an accurate FE model was demonstrated. The results are in agreement with previous studies analysing two-dimensional meshing

Pounding between adjacent buildings of varying height coupled through soil

Pounding between adjacent buildings is a significant challenge in metropolitan areas because buildings of different heights collide during earthquake excitations due to varying dynamic properties and narrow separation gaps. The seismic responses of adjacent buildings of varying height, coupled through soil subjected to earthquake-induced pounding, are evaluated in this paper. The lumped mass model is used to simulate the buildings and soil, while the linear visco-elastic contact force model is used to simulate pounding forces. The results indicate while the taller building is almost unaffected when the shorter building is very short, it suffers more from pounding with increasing height of the shorter building. The shorter building suffers more from the pounding with decreasing height and when its height differs substantially from that of the taller building. The minimum required separation gap to prevent pounding is increased with increasing height of the shorter building until the buildings become almost in-phase. Considering the soil effect; pounding forces are reduced, displacements and story shears are increased after pounding, and also, minimum separation gap required to prevent pounding is increased

The importance of intervertebral disc material model on the prediction of mechanical function of the cervical spine

Abstract Background Linear elastic, hyperelastic, and multiphasic material constitutive models are frequently used for spinal intervertebral disc simulations. While the characteristics of each model are known, their effect on spine mechanical response requires a careful investigation. The use of advanced material models may not be applicable when material constants are not available, model convergence is unlikely, and computational time is a concern. On the other hand, poor estimations of tissue’s mechanical response are likely if the spine model is oversimplified. In this study, discrepancies in load response introduced by material models will be investigated. Methods Three fiber-reinforced C2-C3 disc models were developed with linear elastic, hyperelastic, and biphasic behaviors. Three different loading modes were investigated: compression, flexion and extension in quasi-static and dynamic conditions. The deformed disc height, disc fluid pressure, range of motion, and stresses were compared. Results Results indicated that the intervertebral disc material model has a strong effect on load-sharing and disc height change when compression and flexion were applied. The predicted mechanical response of three models under extension had less discrepancy than its counterparts under flexion and compression. The fluid-solid interaction showed more relevance in dynamic than quasi-static loading conditions. The fiber-reinforced linear elastic and hyperelastic material models underestimated the load-sharing of the intervertebral disc annular collagen fibers. Conclusion This study confirmed the central role of the disc fluid pressure in spinal load-sharing and highlighted loading conditions where linear elastic and hyperelastic models predicted energy distribution different than that of the biphasic model