体外预应力CFRP筋自密实混凝土梁的预应力损失

PRESTRESS LOSS OF SELF-COMPACTING CONCRETE BEAMS REINFORCED WITH EXTERNAL CFRP TENDONS

通过体外预应力筋的预应力损失理论计算、试验监测和有限元数值模拟等方法,对体外预应力CFRP筋自密实混凝土(SCC)梁的预应力损失展开研究。共设计6根自密实混凝土试验梁和2根普通混凝土试验梁,研究在不同预应力水平、不同混凝土强度等级下体外CFRP筋预应力损失的规律以及与普通混凝土预应力损失的差别,并将试验值与理论值、有限元值(包括锚固损失、温差损失、松弛损失、收缩及徐变损失)进行对比。结果表明:锚固损失的理论值偏大,理论公式同样适用于CFRP筋,但参数取值应通过实测确定。温差损失公式计算出的CFRP筋与SCC线膨胀系数差值为实际值的500%左右,理论公式不再适用于FRP-SCC梁。CFRP筋松弛损失和SCC收缩徐变损失之和的理论值与试验值相差20%左右,但该理论公式对于强度等级为C65的SCC试件误差较大。CFRP筋预应力损失随预应力水平的减小而减小,减幅最大为15.2%;预应力损失随着混凝土强度等级的提高而增大,其增幅最大为10.4%;普通混凝土试件的预应力损失大于SCC试件,差值最大为11%。

This study aimed to provide a comprehensive experimental,analytical and numerical investigation of prestress loss of self-compacting concrete(SCC)beams with external CFRP tendons.A total of 6 specimens of SCC beams and 2 specimens of controlling beams were designed and tested to get the laws of prestress loss,including anchorage loss,temperature difference loss,relaxation loss,shrinkage loss and creep loss of CFRP bars,at different prestressing and concrete strength levels.The comparison of prestress loss between self-compacting concrete and controlling beams were also made.The results show that the theoretical value of anchorage loss is larger than actual value.The formulas for controlling beams are also suitable for CFRP tendons,while some parameters in the formulas should be determined by tests.Linear expansion coefficient of CFRP bars and SCC calculated by the temperature difference loss formula was about 500%bigger than the actual value.So the formulas for controlling beams are no longer suitable for FRP-SCC components.The total theoretical loss of relaxation of CFRP bars,shrinkage and creep of concrete were about 20%different from the test results,while the theoretical formula exhibited the larger error for the SCC specimens of concrete with the strength level of C65.The loss of external prestress of CFRP bars decreased with the decrease of prestress level,and the maximum reduction of prestress loss is 15.2%.The prestress loss increased with the increase of concrete strength,with the maximum increase of 10.4%.The prestress loss of controlling concrete specimens is greater than that of SCC specimens,and the maximum difference is 11%.