非均匀收缩徐变机理及其对钢-再生混凝土组合梁长期性能影响

The application of composite steel-recycled concrete beams can reduce the life-cycle carbon footprint of buildings and increase the rate of recycling waste concrete. Recycled concrete has larger shrinkage and creep deformations than those of natural concrete, in which case research efforts should be devoted to the long-term behaviour of composite steel-recycled concrete beams; furthermore, non-uniform shrinkage and creep profiles develop through the concrete thickness due to the impermeable steel decking, however, the relative research work of their effects on the long-term behaviour of composite beams is only at start stage. This project will focus on the mechanics of non-uniform shrinkage and non-uniform creep, and the combined effects of non-uniform shrinkage, non-uniform creep, interface slippage and concrete cracking on the long-term behaviour of composite beams. For this purpose, long-term tests and theoretical analysis will be conducted. Non-uniform shrinkage and non-uniform creep models will be proposed for composite beams, based on the corresponding relative humidity distributions through the thickness of concrete with their soffit sealed; the calculation model of long-term interface slippage will be established, and design procedures will be proposed considering the combined effects of non-uniform shrinkage, non-uniform creep, interface slippage and concrete cracking. The research in this project will improve the designing theory of composite steel-concrete beams, and is expected to contribute to the engineering applications of composite steel-recycled concrete beams.

推广应用钢-再生混凝土组合梁可有效降低建筑全寿命周期碳排放，提高废弃混凝土资源化率。再生混凝土收缩徐变较普通混凝土显著增大，钢-再生混凝土组合梁长期性能需重点关注；由于压型钢板的单面密闭作用，组合梁中混凝土收缩徐变沿截面高度非均匀分布，该非均匀分布对组合梁长期性能的影响研究刚刚起步。本项目将以钢-再生混凝土组合梁为研究对象，揭示组合梁中混凝土发生非均匀收缩与非均匀徐变的机理，量化非均匀收缩、非均匀徐变、界面相对滑移及混凝土开裂对组合梁长期性能的耦合影响。为此，进行组合梁长期性能试验研究与理论分析，量化单面密闭混凝土相对湿度沿截面高度的分布，据此提出非均匀收缩与非均匀徐变预测模型；建立组合梁长期界面相对滑移计算模型，并提出考虑非均匀收缩、非均匀徐变、界面相对滑移及混凝土开裂耦合影响的组合梁长期性能设计方法。本项目研究成果可进一步完善组合梁的设计理论，推进钢-再生混凝土组合梁的工程应用。

推广应用钢-再生混凝土组合梁可有效降低建筑全寿命周期碳排放，提高废弃混凝土资源 化率。再生混凝土收缩徐变较普通混凝土显著增大，钢-再生混凝土组合梁长期性能需重点关 注；由于压型钢板的单面密闭作用，组合梁中混凝土收缩徐变沿截面高度非均匀分布，该非均 匀分布对组合梁长期性能的影响研究刚刚起步。项目将以钢-再生混凝土组合梁为研究对象，（a）开展了单面密闭素混凝土长期收缩试验，实测试件不同深度处的收缩与相对湿度，考虑再生粗骨料取代率、试件高度以及截面形状的影响。量化了再生粗骨料取代率对非均匀收缩分布的影响，提出了适用于组合梁设计应用的非均匀收缩模型；进而基于理论分析，提出了适用于组合梁设计应用的非均匀徐变模型。（b）开展了组合梁推出试验，实测试件的荷载-滑移曲线，考虑再生粗骨料取代率、长期荷载以及组合板形式等参数，研究再生粗骨料取代率对组合梁界面相对滑移和极限承载力的影响；采用ABAQUS软件建立组合梁推出试验“热-力”耦合模型，建立了钢-再生混凝土组合梁界面长期相对滑移计算模型。（c）开展了组合梁长期性能试验，实测组合梁挠度、应变、界面相对滑移及裂缝分布形式，参数包括再生粗骨料取代率、组合板高度和楼板形式，研究收缩徐变类型和再生粗骨料取代率对组合梁长期性能的影响；基于MATLAB软件建立组合梁非线性模型，研究非均匀收缩、非均匀徐变、界面相对滑移及混凝土开裂对组合梁长期性能的耦合影响；提出钢-再生混凝土组合梁长期性能的成套设计方法。研究成果可进一步完善组合梁的设计理论，推进建筑固废得到的再生混凝土的结构化应用。