Modeling the effect of random environmental influences on stochastic creep in concrete members

The most significant contribution to the variability of long-term creep for in-situ structural concrete members stems from the effect of environmental influences. Many of these external processes are both seasonal and random. Specifically, ambient temperature, relative humidity, and wind are key factors with regard to creep response. But the influencing factors also include the time of casting/construction, the severity and the extent of seasonality, the exposure characteristics of the concrete member, the geographic location of the structure together with its prevailing meteorological regime, and the correlation between temperature and humidity. In order to investigate the impact of these various factors on the net macroscopic creep coefficient used in analysis and design, a discretized 2D physical model is developed, formulated in term of combined heat transfer and moisture diffusion. The "local" strain response throughout the structural element in space/time is then transformed to a section-wide temporal creep response. The analysis model is then subject to both seasonal and stochastic processes for the triplet variables : ambient temperature, ambient relative humidity, and ambient wind conditions. By modifying various main meteorological features, construction time, dimensional/exposure variables, and stochastic process parameters, we are able to estimate the sectional creep response and, most importantly, the resulting net uncertainty regarding creep as a function of time