School of Urban Construction, Yangtze University, Jingzhou 434023, China.
Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA.
Sensors (Basel). 2018 May 23;18(6):1682. doi: 10.3390/s18061682.
Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force⁻time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads.
冲击荷载会对土木工程结构的安全性产生重大影响，例如钢管混凝土（CFST）柱。研究 CFST 柱在冲击荷载下的力学行为和应力分析对于确保其免受此类荷载的安全非常重要。目前，冲击荷载下 CFST 柱混凝土芯部的内部应力监测仍然是一个极具挑战性的课题。本文研制了一种 PVDF（聚偏二氟乙烯）压电阻尼智能传感器，并成功应用于监测冲击荷载下 CFST 柱混凝土芯部的内部应力。智能传感器由夹在两片薄钢板之间的 PVDF 压电薄膜通过环氧树脂组成。这种保护不仅可以防止 PVDF 薄膜受到冲击损坏，还可以确保其绝缘和防水。智能传感器在混凝土浇筑过程中嵌入圆形钢管混凝土试件中。对试件进行了冲击荷载试验，并采集了测试数据。与冲击锤的冲击力-时间曲线相比，从 PVDF 智能传感器获得的应力时程揭示了冲击荷载下核心混凝土内部应力的演化。还对冲击过程进行了非线性有限元模拟。有限元模拟的结果与试验结果吻合较好。结果表明，所提出的 PVDF 压电阻尼智能传感器可以有效地监测冲击荷载下钢管混凝土柱的内部应力。
