Abstract
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.
Highlights
Concrete-filled steel tubes (CFSTs), which combine the superior performances of steel and concrete, have been widely researched and applied in civil engineering [1,2]
It is of great meaning to develop a sensor which can monitor the internal stress of the concrete core to analyze the mechanical behavior and failure mechanism of CFST structures
Circular CFSTs with different heights and wall thicknesses were tested by impact tests
Summary
Concrete-filled steel tubes (CFSTs), which combine the superior performances of steel and concrete, have been widely researched and applied in civil engineering [1,2]. The load bearing capacity of a CFST structure for normal static loads is less than its capacity against short duration dynamic loads, such as impact loads [3,4,5,6]. The structural deformation and the evolution of internal stress under an impact load are different from those under static loads or long duration dynamic loads. Taking CFST piers and CFST piles as examples, these CFST structures are basically subject to axial impact loads during the construction process with the hammering method. It is of great meaning to develop a sensor which can monitor the internal stress of the concrete core to analyze the mechanical behavior and failure mechanism of CFST structures. Common stress monitoring devices include strain gauges, Fiber Bragg Grating (FBG)
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