Research On The Behavior And Calculation Model Of Shrinkage Creep In Plain Concrete And RC Cylinders

The shrinkage and creep mechanism of concrete is complex and with manyuncertain factors, it is one of the main reasons for causing large deflection of middlespan in the prestressed concrete girder bridge. In order to improve awareness aboutthe performance of concrete girder bridge which caused by shrinkage and creep, inthis paper, through a long-term experimental study on a large number of concrete andreinforced concrete members, summed up the long-term time-varying law ofshrinkage and creep for concrete and reinforced concrete, put forward calculationmodel of shrinkage and creep in concrete and reinforced concrete cylinders, theprediction results is greatly improved than other models. The main research contentis as follows:（1）Through long-term tests for the shrinkage strain of concrete circularcolumns specimens and long-term creep experiment of concrete circular columnswith different loading ages was done, abtained the change rule of concrete shrinkageand creep with a long time, Based on the contrastive study of International anddomestic prediction models with B3coefficient of variation and B3variance, the newprediction model of the concrete shrinkage strain is proposed,. at the same timeCEB-FIP(1990) model of concrete creep is corrected.（2）Through contrast test of creep with6concrete(reinforced concrete) circularcolumns, research on creep properties of reinforced concrete columns, the measureddata is fitted by regression analysis combined with the model of CEB-FIP （1990）and the China Institute of building, calculated influence coefficient of concrete creepcaused by reinforcement in the different loading ages, contrasted with the Dischingermethod which time-dependent function used CEB-FIP（1990） model and ChinaInstitute of building model.Test result shows:(1) Creep coefficient of reinforced concrete are less thanplain concrete in the same loading age, the loading age have low influence onreinforced concrete creep coefficient in later stage.(2) The creep prediction modelsat home and abroad with short-term loading age(9d) have high predictive accuracyfor creep coefficient. The creep prediction models at home and abroad with long-termloading age(39d) have low predictive accuracy for creep coefficient, especiallypredicted values of creep coefficient are general insufficient in late stage. Thepredictive effect of GZ(1993) model is best.(3) The influence coefficient of concrete shrinkage and creep caused by reinforcement is low prediction in Dischinger method,and it is low to predict the creep deformation under different loading.