折线先张法预应力混凝土梁长期挠度实用计算公式

Calculation Model for Long-term Deflection of Prestressed Concrete Beam with Pretensioned Bent-up Tendons

精确的长期挠度计算方法是折线先张梁推广应用的重要条件之一.通过对放置于不同工作环境中的三根折线先张梁长期加载,研究了跨中挠度及跨中截面徐变应变,结合前期建立的梁挠曲徐变系数与其徐变挠度系数两系数间的数学模型,进一步分析了折线先张梁的长期挠度系数、挠曲徐变应变系数及徐变挠度系数三系数间的数值关系.结果表明:折线先张梁长期挠度系数约为其徐变挠度系数的1.1倍,建立了考虑混凝土的收缩、徐变及梁的预应力度值、预应力产生的轴力值、预应力产生的弯矩值、构件换算截面面积及构件截面抗弯模量等多因素共同影响的折线先张梁长期挠度实用计算公式.

Precisely predicting the long term deflection is one of the most important advantages of prestressed concrete beam with pretensioned bent-up tendons. By loading three prestressed concrete beams with preten- sioned bent-up tendons in a long term, the mid-span deflection and section creep strain were studied. Together with the numerical relationship expression between creep coefficient and creep deflection coefficient which was established earlier, the numerical relationships among creep coefficient, long-term deflection coefficient, and creep deflection coefficient were further studied. The results show that： The value of the long-term deflection coefficient is 1.1 times that of the creep coefficient. Finally, a practical expression was derived for calculating the long-term deflection of prestressed concrete beam with pretensioned bent-up tendons, which took a number of influencing factors into consideration, such as concrete shrinkage, concrete creep, partially prestressed ratios, the axial compression and the moment value due to prestressing, component equivalent sectional area and the section modulus of bending, etc..