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Long-term Behaviour (long-term + behaviour)
Selected AbstractsFinite elements modelling of the long-term behaviour of a full-scale flexible pavement with the shakedown theoryINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2009Cyrille Chazallon Abstract Rutting, due to permanent deformations of unbound materials, is one of the principal damage modes of low-traffic pavements. Flexible pavement design methods remain empirical; they do not take into account the inelastic behaviour of pavement materials and do not predict the rutting under cyclic loading. A simplified method, based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings, has been used to estimate the permanent deformations of unbound granular materials subjected to traffic loading. Based on repeated load triaxial tests, a general procedure has been developed for the determination of the material parameters of the constitutive model. Finally, the results of a finite elements modelling of the long-term behaviour of a flexible pavement with the simplified method are presented and compared with the results of a full-scale flexible pavement experiment performed by Laboratoire Central des Ponts et Chaussées. Finally, the calculation of the rut depth evolution with time is carried out. Copyright © 2008 John Wiley & Sons, Ltd. [source] Non-local dispersive model for wave propagation in heterogeneous media: one-dimensional caseINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2002Jacob Fish Abstract Non-local dispersive model for wave propagation in heterogeneous media is derived from the higher-order mathematical homogenization theory with multiple spatial and temporal scales. In addition to the usual space,time co-ordinates, a fast spatial scale and a slow temporal scale are introduced to account for rapid spatial fluctuations of material properties as well as to capture the long-term behaviour of the homogenized solution. By combining various order homogenized equations of motion the slow time dependence is eliminated giving rise to the fourth-order differential equation, also known as a ,bad' Boussinesq problem. Regularization procedures are then introduced to construct the so-called ,good' Boussinesq problem, where the need for C1 continuity is eliminated. Numerical examples are presented to validate the present formulation. Copyright © 2002 John Wiley & Sons, Ltd. [source] The resonant structure of Jupiter's Trojan asteroids , I. Long-term stability and diffusionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006P. Robutel ABSTRACT We study the global dynamics of the jovian Trojan asteroids by means of the frequency map analysis. We find and classify the main resonant structures that serve as skeleton of the phase space near the Lagrangian points. These resonances organize and control the long-term dynamics of the Trojans. Besides the secondary and secular resonances, that have already been found in other asteroid sets in mean motion resonance (e.g. main belt, Kuiper belt), we identify a new type of resonance that involves secular frequencies and the frequency of the great inequality, but not the libration frequency. Moreover, this new family of resonances plays an important role in the slow transport mechanism that drives Trojans from the inner stable region to eventual ejections. Finally, we relate this global view of the dynamics with the observed Trojans, identify the asteroids that are close to these resonances and study their long-term behaviour. [source] A multiphase finite element simulation of biological conversion processes in landfillsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Tim Ricken Worldwide, landfills are the most common way to dispose of waste, but have an impact on the environment as a result of harmful gas and leachate production. Estimating the long-term behaviour of a landfill in regard to this gas production and organic degrading, as well as to settlement and waste water production, is of high importance. Therefore, a model has been developed to simulate these processes. This constitutive model is based on the multiphase Theory of Porous Media. The body under investigation consists of an organic and an inorganic phase as well as a liquid and a gas phase. The equations of the model are developed on the basis of a consistent thermo-mechanical approach including the momentum balance for the solid phase and the mixture, the energy balance for the mixture and the mass balance for the gas phase. All interactions between the constituents such as mass transfers, interaction forces and energy fluxes are taken into consideration. The strongly coupled set of partial differential equations is implemented in the finite element code FEAP. The theoretical framework and the results of meantime successfully performed simulation of a real landfill body will be shown. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hygrothermische Beanspruchung und Lebensdauer von Wärmedämm-VerbundsystemenBAUPHYSIK, Issue 3 2006Leiter Abt. Das Alterungsverhalten und die Lebensdauer von Fassadensystemen wird stark von der hygrothermischen Beanspruchung beeinflußt. Neben den Witterungsbedingungen Temperatur, Strahlung und Luftfeuchte wirken häufig auch noch äußere oder innere Feuchtequellen, z. B. Schlagregen, Baufeuchte oder Oberflächenbetauung auf Außenwände ein. Wegen ihrer geringen Masse sind Wärmedämm-Verbundsysteme (WDVS) davon z. T. besonders betroffen. Dennoch zeigt die Langzeitstudie an Objekten mit WDVS, daß damit keine erhöhte Schadensanfälligkeit verbunden ist. Abgesehen von einigen optischen Mängeln ist das Langzeitverhalten von WDVS als sehr positiv zu bewerten. Bei regelmäßiger Wartung entspricht die Lebensdauer von WDVS der von herkömmlich verputzten Außenwänden. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Hygrothermal loads and service life of external wall insulation systems. Service life and aging behaviour of external wall systems depend on their hygrothermal loads. Apart from the fluctuating climatic conditions temperature, solar radiation and humidity there are often additional exterior or interior sources of moisture, e.g. driving rain, construction moisture or surface condensation acting on facades. External wall insulation systems (ETICS = E xternal T hermal I nsulation C omposite S ystems) are especially affected due to their low mass. However, the long-term observation by repeated inspections of the same objects over a period of 30 years proves that ETICS show not more damage than traditional facades. Apart from minor esthetical problems due to soiling or microbial growth their long-term behaviour is very encouraging. Maintained at normal intervals ETICS are as durable as traditionally rendered masonry walls. [source] Vereinfachtes Verfahren zur Vorhersage des Langzeitverhaltens von Holz-Beton-VerbundkonstruktionenBAUTECHNIK, Issue 4 2005Ralf Avak Prof. Dr.-Ing. Für die Bemessung von nachgiebig verbundenen Biegeträgern aus Holz und Beton wird vom praktisch tätigen Ingenieur in der Regel das ,-Verfahren bevorzugt. Das Verfahren ist Bestandteil nationaler, sowie europäischer Holzbauvorschriften [4], [5]. Für die Berechnung des Langzeitverhaltens ist das ,-Verfahren in seiner derzeitigen Form jedoch nur bedingt geeignet, da es z. B. das Schwinden des Betons nicht berücksichtigt. Im folgenden wird aus diesem Grund ein einfaches analytisches Verfahren vorgestellt, bei dem neben dem Kriechverhalten der Materialien Holz und Beton auch deren Schwind- bzw. Quellverformungen sowie das Langzeitverhalten der Schubverbindungsmittel berücksichtigt werden können. Die Anwendung des Verfahrens ist momentan noch auf Innenbauteile beschränkt. Simplified procedure for the description from the long-term behaviour of timber-concrete composite structures. The ,-procedure is favoured to design timber-concrete composite structures. This procedure is component of current national as well as European timber standards [4], [5]. The ,-procedure isn't suitable to describe the long-term behaviour, because it does not consider the shrinkage of concrete for example. A simplified procedure is introduced in the following. This procedure considers creeping of timber and concrete and , for the first time , swelling and shrinkage of these materials, as well as the long-term behaviour of the shear connectors. Currently it is applicable only to inner structures. [source] Long-term follow up of children exposed in utero to nifedipine or ritodrine for the management of preterm labourBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 3 2006BA Houtzager Objective, To compare the long-term psychosocial and motor effects on children exposed in utero to nifedipine or ritodrine for the management of preterm labour. Design, Randomised controlled trial. Setting, Multicentre study in two university and one primary hospital in the Netherlands. Population, In the original trial, 185 women were randomised to either nifedipine (n= 95) or ritodrine (n= 90). Of the 185 liveborn children, 171 survived (92%), and of these 102 (61%) were followed up at age 9,12 years. Methods, Age-specific questionnaires were administered to the parent and teacher. Additional data were obtained from medical records. Main outcome measures, Questionnaires were used to assess the child's behavioural,emotional problems, quality of life (QoL), motor functioning, parenting distress and the child's education. Results, Of the 171 eligible families, 102 (61%) agreed to participate and completed the questionnaires. Response was equal in the ritodrine group (n= 54 of 83 surviving children, 65%) compared with the nifedipine group (n= 48 of 88 surviving children, 55%). After controlling for differing perinatal characteristics at birth, no significant differences between the groups were detected with respect to long-term behaviour,emotional outcome, QoL, education, motor functioning or parenting distress. Psychosocial outcome was slightly better in the nifedipine group. Conclusions, The results do not support any differential postnatal effect of the tocolytic agents ritodrine or nifedipine on the child's long-term psychosocial and motor functioning. The slightly better outcome of children randomised in the nifedipine group is most likely due to more favourable perinatal outcomes in this group. These results merit further investigation in a larger group of survivors. [source] | ||||||||||