Un élément fini de poutre fissurée application à la dynamique des arbres tournants

International audienceDans ce travail on présente une méthode originale de construction d'un élément fini de poutre affectée de fissurations. La souplesse additionnelle due à la présence des fissures est identifiée à partir de calculs éléments finis tridimensionnels tenant compte des conditions de contact unilatéral entre les lèvres. Cette souplesse est répartie sur toute la longueur de l'élément dont on se propose de construire la matrice de rigidité. La démarche permet un gain considérable en temps de calcul par rapport à la représentation nodale de la section fissurée lors de l'intégration temporelle de systèmes différentiels en dynamique des structures

The Corinth Rift Laboratory, Greece (CRL): A Multidisciplinary Near Fault Observatory (NFO) on a Fast Rifting System

The western rift of Corinth (Greece) is one of the most active tectonic structures of the euro-mediterranean area. Its NS opening rate is 1.5 cm/yr ( strain rate of 10-6/yr) results into a high microseismicity level and a few destructive, M>6 earthquakes per century, activating a system of mostly north dipping normal faults. Since 2001, monitoring arrays of the European Corinth Rift Laboratory (CRL, www.crlab.eu) allowed to better track the mechanical processes at work, with short period and broad band seismometers, cGPS, borehole strainmeters, EM stations, …). The recent (300 kyr) tectonic history has been revealed by onland (uplifted fan deltas and terraces) and offshore geological studies (mapping, shallow seismic, coring), showing a fast evolution of the normal fault system. The microseismicity, dominated by swarms lasting from days to months, mostly clusters in a layer 1 to 3 km thick, between 6 and 9 km in depth, dipping towards north, on which most faults are rooting. The diffusion of the microseismicity suggests its triggering by pore pressure transients, with no or barely detected strain. Despite a large proportion of multiplets, true repeaters seem seldom, suggesting a minor contribution of creep in their triggering, although transient or steady creep is clearly detected on the shallow part of some majors faults. The microseismic layer may thus be an immature, downward growing detachment, and the dominant rifting mechanism might be a mode I, anelastic strain beneath the rift axis , for which a mechanical model is under development. Paleoseismological (trenching, paleoshorelines, turbidites), archeological and historical studies completed the catalogues of instrumental seismicity, motivating attempts of time dependent hazard assessment. The Near Fault Observatory of CRL is thus a multidisciplinary research infrastructure aiming at a better understanding and modeling of multiscale, coupled seismic/aseismic processes on fault systems.Grant for Researchers (CC) ID 188753

Annals of Solid and Structural Mechanics

In this paper, the effects of a breathing crack on the vibratory characteris- tics of a rotating shaft are investigated. A new, simple and robust model composed of two rigid bars connected with a nonlinear flexural spring is proposed. The nonlinear spring, located at the cracked transverse section position, concentrates the global stiff- ness of the cracked shaft. The breathing mechanism of the crack is described by a more realistic periodic variation of the global stiffness depending not only but substantially on the system vibratory response. It is based on an energy formulation of the problem of 3D elasticity with unilateral contact conditions on the crack lips. A possible partial opening and closing of the crack is considered which makes the approach more appro- priate for deep cracks modeling. The harmonic balance method, direct time-integration schemes and nonlinear dynamics tools are used to characterize the global dynamics of the system. The effects of the crack depth and rotating frequency have been metic- ulously examined and it was found that the cracked shaft never exhibits chaotic or quasi-periodic vibratory response

Effects of music therapy on occupational stress and burn-out risk of operating room staff

The operating theatre staff is exposed to various constraints such as excessive working hours, severe medical conditions and dreadful consequences in case of malpractice. These working conditions may lead to high and chronic levels of stress, which can interfere with medical staff well-being and patients quality of care. The aim of this study is to assess the impact of music therapy on stress levels and burn-out risk on the operating room staff. This is a pre-experimental study including the operating rooms staff of urology and maxillofacial surgery in the academic hospital of Sahloul Sousse (Tunisia) over a period of six weeks. The study consisted of three phases. The first was an initial assessment of stress level with a predefined survey. The second included three music therapy sessions per day over one month. The third was an immediate stress level reassessment following the intervention. Stress levels were evaluated using the Perceived Stress Scale version PSS-10 and the Maslach Burnout Inventory. The overall response rate was 73.9%.The average age of the study population was 37.8 ± 7.7 years with a female predominance (64.7%). After the music therapy program, Perceived Stress Scale average score decreased from 22 ± 8.9 to 16 ± 7.9 (p = 0.006). Concerning the burnout, only the average score of emotional exhaustion decreased signifi- cantly from 27 ± 10.8 to 19.2 ± 9.5 (p = 0.004). Music therapy is an innovative approach that seems to reduce operating theatre staff stress. It must be considered as a non pharmacological, simple, economic and non invasive preventive tool