COMPARISON AND ANALYSIS OF CONCRETE CREEP MODELS UNDER WET-DRY CYCLE EFFECT

According to the basic theory of concrete creep, environmental relative humidity is the most important factor which effects drying creep of total creep. So far, researchers have put forward the creep prediction models such as ACI209R-92, B3, BP-KX and CEB-FIP1990, etc., which have been adopted as the standards for concrete design in the United States, RILEM, European countries and China. However, in these models, relative humidity is put into consideration as an approximate constant, so it results in that these models are unavailable to calculate concrete creep under continuous changes of environmental relative humidity. In this paper a new creep prediction model based on B3 is presented and the characteristics of concrete creep under wet-dry cycle and the influential factors on concrete creep (e.g. material strength, stress ratio, wet-dry cycle and variation amplitude of environmental relatively humidity, etc.) are considered rationally. By introducing BP-KX model and creep model based on developed microprestress-solidification theory, the other two for prediction of creep under wet-dry cycle, in combination with the comparison and analysis of the predicted results and the experimental values, the characteristics, shortages and applicability of these models are concluded respectively in this paper.