新型缓粘结预应力体系试验研究

Experimental research on a new type of bond-retarded prestressed system

本文介绍了缓凝期为20d、30d和40d,最终抗压强度在30MPa以上,能满足缓粘结预应力体系要求的超效缓凝砂 浆,并对这种特种砂浆进行了系统的工程性能试验;提出了一种缓粘结预应力钢筋制作工艺,并对这种制作工艺制成的缓 粘结预应力筋进行了拉拔试验,给出了缓粘结预应力混凝土结构不同龄期下张拉预应力筋所需克服的摩擦阻力的范围, 为这一新型的预应力体系在设计中张拉摩阻力计算提供了依据;用这种缓粘结预应力筋制成的16根缓粘结预应力受弯 构件进行试验,从开裂弯矩、极限弯矩、裂缝形式和荷载-挠度曲线等方面,把缓粘结预应力构件与传统的后张法(有粘 结、无粘结)预应力构件进行了对比分析,得出了缓粘结预应力构件在张拉两个月后,其工作性能与有粘结预应力构件几 乎一样的结论,为这一新型预应力体系的设计提供了依据。

A super-duty retarded mortar with its retarded-set period of 20, 30 and 40 days respectively and its final compressive strength above 30MPa, which can meet the requirements of the bond-retarded prestressed system, are introduced. A series of systematical tests of its engineering behavior were performed. A special technique for manufacturing the corresponding bond-retarded prestressed tendon was also developed with drawing tests carried out accordingly. The range of friction which needs to be counteracted by the bond-retarded prestressed concrete structures of different ages is presented, it offers a fundamental basis for the calculation of friction in drawing in the case of practical design. A group of tests were conducted on 16 bond-retarded prestressed flexural members using special bond-retarded prestressed tendons and compared to conventional prestressed members with bonded post-tensioning and non-bonded post-tensioning in cracking moment, ultimate moment, cracking forms and load-deflection curves, etc. A conclusion is reached that two months after the drawing, the bond-retarded prestressed members has almost the same working performances as that of the bonded post-tensioned members, which provides an important reference for the design of this new type of prestressed system.