Demographic change and transformations of the active life cycle: what relations?

Historical changes in the typical life-cycle do not conform to a simple model of equal-sharing in which additional years of life are equally distributed between time devoted to training, work and leisure. We have instead observed a quasi-general decline in the share of our life-cycles that is devoted to labour. The major reason for such a deviation is the fact that this life-cycle evolves in response to other factors, such as productivity, preferences and conditions for the accumulation and depreciation of human capital. We investigate the articulation of these different factors in a continuous-time model of life-cycle optimisation that allows a realistic treatment of demographic structure. The main motives for the contraction of working lives are global productivity and the importance of human capital depreciation. We show that the equal-sharing scenario requires a parallel evolution of productivity and consumption norms, and a slowing-down of human capital depreciation that is consistent with the change in life expectancy.Ageing, life-cycle, training, retirement age

Innovation pour les ouvrages ferroviaires en France :une poutre mixte préfléchie en BTHP, Innovation for the railway bridge decks in France :a precambered composite beam in VHPC

info:eu-repo/semantics/publishe

Test up to ultimate limit state and failure of innovative prebended steel-VHPC beams for railway bridges decks

info:eu-repo/semantics/publishe

Alternate fatigue response of VHPC for innovative composite pre-bended beams applied to railway bridges decks

5th International conferenceinfo:eu-repo/semantics/publishe

Innovation pour les ouvrages ferroviaires :une poutre mixte préfléchie en BTHP

info:eu-repo/semantics/publishe

Innovation for the Railway Bridge Decks: A Prebent Steel-–VHPC Beam

An extensive experimental study has been carried out in the framework of the French National Project MIKTI devoted to innovative composite structures to extend the Belgian technique of composite prebent beams called "preflex" beams, to very high performance concrete (VHPC). By comparison with experience gained from the Belgian precast industry, the main advantage of using VHPC with silica fume is to reduce the prestressing losses of the system, thanks to a significant decrease of the creep in addition to the possibility of optimizing the weight and the span of the beam. Major issues of the research were to validate a design method at serviceability state related to concrete cracking and at ultimate limit state corresponding to instability of the steel girder and the preservation of the composite behaviour of the beam even after a large number of live load cycles. The analysis of the global response of two 13 m long beams monitored during several months allowed to conclude the feasibility to optimize a prebent beam with a VHPC.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effect of applied stresses on alkali-silica reaction-induced expansions

International audienceThe mechanical effects of alkali-silica reaction (ASR) have to be modeled in order to assess the deterioration level and the stability of ASR-damaged concrete structures. Several experimental programs have shown the effects of compressive stresses on ASR-induced strains. The effect is so significant that assessment models have to take into account the modification of ASR expansions due to applied stresses and the consequences on the mechanical response of damaged structures. This paper presents and analyzes measurements performed on concrete specimens subjected to several states of stresses along the three directions (due to applied stresses and to passive restraint). Mechanical calculations show that the volumetric expansion imposed by ASR is constant whatever the stresses conditions. They point out the “expansion transfer” occurring along the directions which are less compressed; thus, the effect of stresses on ASR expansions anisotropy can be precisely quantified. (C) 2005 Elsevier Ltd. All rights reserved