混凝土收缩应变预测模型研究

Study on Prediction Model of Concrete Shrinkage Strain

通过对混凝土圆柱试件收缩应变的长期测试发现,试件的体内收缩应变普遍小于体外收缩应变,而且收缩应变在前期增长较快,后期收缩应变率逐步减小,最后曲线趋于平缓;20d龄期的体内、外收缩应变分别占最大收缩应变的10.8%和13.3%,100d龄期的体内、外收缩应变分别占最大收缩应变的36.5%和37.7%,1年龄期的体内、外收缩应变分别占最大收缩应变的83.2%和80.9%。在用B3变异系数和B3方差对国内外的收缩应变预测模型进行对比研究的基础上,提出新的混凝土收缩应变预测模型。该预测模型综合了GZ(1993)模型的对数函数计算理论和GL2000模型的双曲线幂函数计算理论,并参考了中国建科院模型的相关参数,因此该模型预测的数据不论初期还是后期与实测数据偏离度均较小,预测收缩应变曲线与实测拟合曲线基本一致,预测精度较其他模型有很大提高。

Through long-term tests for the shrinkage strain of concrete circular column specimens, weve found that internal shrinkage strain is generally less than external shrinkage strain. Furthermore, the shrinkage strains grow rapidly in earlier stage and gradually reduce in later stage, and the curve tends to be flat at last. The internal and external shrinkage strains take up 10.8% and 13.3% of the maximum shrinkage strain respectively in 20 days, 36.5% and 37. 7% respectively in 100 days, 83.2% and 80. 9% respectively in a year. Based on the contrastive study of international and domestic prediction models for shrinkage strain with B3 coefficient of variation and B3 variance, a new prediction model for concrete shrinkage strain is proposed. The new model has integrated the logarithmic function calculation theory of the GZ （1993） model with the hyperbolic function theory of GL2000 model. At the same time, related parameters of the model developed by China Academy of Building Research are used as references. Thus, the predicted data by the new model deviate less from measured data no matter in earlier stage or in later stage. The pre- dicted shrinkage strain curves basically agree well with measured fitting curves and the prediction accuracy has been greatly improved compared with other models.