基于SMA的智能预应力梁主动控制试验研究

Experimental study on active control of intelligent prestressed beams with SMA

在工程结构的长期使用过程中,随着外部荷载及温度、湿度等环境条件的变化,材料与结构性能会发生退化,这就要求结构具有一定的智能特性以适应上述变化。针对这一问题,提出一种新型智能预应力结构——形状记忆合金智能预应力梁,将形状记忆合金以体外预应力筋的形式布置在钢筋混凝土梁体外,利用形状记忆合金在相变过程中产生的回复力对梁施加驱动力。进行2根形状记忆合金智能预应力梁的主动控制试验。试验结果表明,通过控制形状记忆合金的温度,可以有效地实现对混凝土梁的变形和裂缝的主动控制。当形状记忆合金的温度分别达到56℃、81℃时,梁的跨中挠度恢复百分比分别为17.3%、8.5%,曲率恢复率分别为11.8%、4.8%,最大裂缝宽度分别减小了14.3%、15.8%。此外,还进行了形状记忆合金智能预应力梁的非线性有限元分析,计算值与试验结果吻合良好。

Structures should have certain intelligent characteristics to adapt to the changes in external loads, environmental conditions, and material deteriorations. A new type of smart prestressed structure, shape memory alloy （SMA） based smart prestressed beam, is proposed. The beam is prestressed with SMA external tendons which produce recovery control force due to phase reverse transformation. Experimental study on two smart SMA tendon prestressed beam specimens were carried out. Test results show that SMA tendons of the two prestressed smart beams can produce beneficial prestressing effect by exerting recovery force to the beams. For the specimen with the temperature of the SMA tendon reaching 56℃, the deflection, curvature and crack width at the mid span of the beam were recovered by17.3% , 11.8%, and 14.3%, respectively. For the specimen with the temperature of the SMA reaching 81℃, these recovery values were 8.5% , 4.8%, and 15.8%, respectively. Nonlinear analysis for the smart SMA prestressed beams was carried out by using FEM and the simulation results were in good agreement with the test data.