形状记忆合金绞线与混凝土的粘结滑移性能及影响因素研究

采用拉拔试验对SMA绞线与混凝土之间的粘结滑移性能进行研究，分析了拉拔试件的破坏模式和受力过程，阐述了SMA绞线与混凝土之间粘结滑移的相互作用机理，讨论了拉拔试件粘结滑移性能随混凝土强度、混凝土保护层厚度、SMA绞线锚固长度以及加载速度的变化规律，建立了SMA绞线锚固长度的计算公式。结果表明:拉拔试件的破坏模式以典型破坏为主，其受力过程分为5个阶段:弹性阶段、转动脱胶阶段、内部拥塞阶段、衰减阶段和残余阶段。同时，随着混凝土强度的增大，试件的极限粘结强度也增大；当保护层厚度达到一定数值后，增加保护层厚度对试件的极限粘结强度几乎没有影响；SMA绞线的锚固长度越大，试件的极限粘结强度越小；试件的极限粘结强度会随着加载速度的增大而小幅增大，若加载速度过快，SMA绞线则会发生散捆断裂。此外，所建立的SMA绞线锚固长度计算公式可以考虑多种影响因素，对SMA绞线用于土木工程结构中需要考虑的锚固、搭接和细部构造等结构设计问题具有一定的理论意义及实用价值。

Investigation on bond-slip behavior and influence factors between shape memory alloy strands and concrete

The pull-out test was carried out to study the bond-slip behavior between SMA strands and concrete. The failure mode and the loading process of the pullout specimens were analyzed. Then, the interaction mechanism between SMA strands and concrete was described. Moreover, the variation of bond-slip behavior of the pullout specimens with concrete strength, concrete cover thickness, anchorage length of SMA strands and loading speed were respectively discussed. Finally, a formula for calculating the anchorage length of SMA strands was established. The results show that the main failure mode of pullout specimens is the typical failure, its loading process can be divided into five stages:elastic stage, rotational degumming stage, internal congestion stage, decaying stage and residual stage. Meanwhile, with the increase of the concrete strength, the ultimate bond strength of specimens also increases; the concrete cover thickness has little effect on the ultimate bond strength when it reaches a certain value; the ultimate bond strength decreases with the increase of the anchorage length of SMA strands; and with the increase of the loading speed, the ultimate bond strength increases slightly, and SMA strands will bundle off and break if the loading speed is too fast. In addition, the formula for calculating the bond length of SMA strands can take into account various influence factors, which has a certain theoretical significance and practical value to the structure design problems such as anchorage, splices and detailing for using SMA strands in the civil engineering.