Constitutive Laws of Consisting Materials and Load-Deformation Mechanism of Pre-stressed Concrete Members

为了预测预应力混凝土受弯构件的荷载-变形关系，研究了反复荷载作用下预应力钢筋的应力-应变关系，约束混凝土在剪力和弯矩作用下的应力-应变特性，以及灌浆与预应力钢筋之间的粘结对预应力混凝土受弯构件受弯性能的影响。得到了以下主要结论：1)提出了PC钢带应变变量的Menegoto-Pinto循环应力应变模型。该模型较好地模拟了不同强度和尺寸的PC钢绞线、拉伸和低温退火(发蓝)PC筋和感应加热淬火PC筋在不同类型的循环荷载作用下的滞回曲线，如递增应变循环荷载、随机循环荷载等。2)在较高剪力水平下，约束混凝土在恒剪切力作用下的单轴应力-应变特性表现出较小的切线弹性、较小的抗压强度和较小的应变。3)提出了精确计算预应力混凝土构件极限抗弯强度的应变协调系数F的计算公式。在沿纵向划分构件的块体单元上，考虑了预应力钢筋与灌浆土之间的粘结滑移特性，对F值进行了研究。分析中采用的参数有预应力筋的形状、直径、灌浆强度等。

For predicting load-deformation relations of pre-stressed concrete flexural members, stress-strain relations of pre-stressing (PC) steels under cyclic loading, stress-strain characteristics of confined concrete subjected to shear force and flexural moment, and effects of bond between grout and PC steel on flexural performance of PC flexural members are investigated. Following main conclusions are obtained.1) The cyclic stress-strain models for PC steels using Menegotto-Pinto expression with variable of strain are proposed. The models estimate satisfactorily hysteretic curve of PC strand, stretched and low temperature annealed (blueing) PC bars and induction heating quenched PC bars of different strength and size under various type of cyclic loading, such as gradual increase strain cyclic loadings, random cyclic loadings etc..2) Uni-axial stress-strain characteristics of confined concrete subjected to constant shear force show smaller tangent modulus, smaller compressive strength and smaller strain at the strength, in the case of higher shear force level. Shear strain of confined concrete under constant shear force increase according to axial stress increment in the case of high compression force level.3) The equations to evaluate F value ( strain compatibility factor) for calculating accurately ultimate flexural strength of pre-stressed concrete members are proposed analytically. The F values are investigated with consideration of bond-slip characteristics between pre-stressing steel and grout, on block elements obtained by dividing the members along longitudinal direction. Employed parameters in the analysis are shape and diameter of pre-stressing steel, strength of grout and so on.