折线先张全预应力混凝土梁徐变曲率试验研究

为了有效地预测折线先张的全预应力混凝土梁徐变挠度,对该类梁的徐变曲率进行了试验研究.通过对2根7.5 m长的折线先张全预应力简支梁进行长期加载,定时观测了2根梁的跨中徐变挠度和不同高度截面的徐变应变,绘制了试验梁的徐变系数和徐变挠度系数时程曲线,并将2个系数进行了对比分析.根据试验粱不同时段跨中截面不同高度的徐变应变实测值,绘制了试验梁不同时段跨中截面弯曲应变徐变图,验证了试验梁长期荷载作用下平截面假定的适用性,并指出徐变作用引起梁跨中截面中和轴的移动情况.基于平截面假定,以根据试验值建立的徐变应变几何模型为研究对象,以曲率参数为纽带,从理论角度推证了徐变挠度系数与徐变系数间的数值关系,与试验结果进行了对比,并提出了在徐变系数已知的情况下徐变挠度系数的计算公式.

Experimental Study on Creep Curvature of Full-prestressed Concrete Beams with Pretensioned Bent-up Tendons

In order to effectively predict the creep deflection of full-prestressed concrete beams with pretensioned bent-up tendons, the creep curvature of such kind of beams was experimental studied. By timed observing the creep deflection at mid-span and the creep swains of sections at different heights of the two 7.5 m full-prestressed concrete simple-supported beams with pretensioned bent-up tendons under long-term loading, the time-history curves of the creep coefficient and the deflection creep coefficient were plotted and compared. According to the measured creep swains at different heights of mid-span section in subsequent time, the flexuml swain creep diagram of cross-section at mid-span in different periods of time was drawn. Then the applicability of the assumption of plane section under long-term loading was proved, and the beam's neutral axis displacement was characterized. Based on the assumption of plane section and the established creep geometry model by experimental result, combined with curvature, the numerical relationship between the deflection creep coefficient and the creep coefficient was deducted and proved, and the calculation formula of the deflection creep coefficient was put forward with the known creep coefficient.