Interfacial Behavior of Steel-Concrete Composite Deck by Fiber Bragg Grating Sensors

Abstract

Experiment plays an important role in studying the nonlinear behaviors of structures, especially for steel-concrete composite structures. In order to study the nonlinear behavior of steel-concrete composite deck, a series of fiber Bragg grating (FBG for shortly) sensors were designed and arranged in a full-scale model of composite deck. Cracks, slip and uplift were measured, respectively. The results show that FBG sensors performed well in the measurement of composite structure test. The arrangement of FBG sensors was much simpler than conventional electrical strain sensors. The response of FBG sensors was sensitive to the variation of structure states. The interfacial slip showed significant nonlinearity. Comparing to interfacial slip, the magnitude of uplift was small. Keywords:Fiber Bragg Grating; Steel-concrete Composite Deck; Interfacial Behavior 1.INTRODUCTIONSteel-concrete composite structure combines the steel girder with the concrete slab by shear connectors. It works as a whole and has good economical and mechanical performance (Al-deen et al., 2011). With the increase of load, slip and uplift will occur on the interface which would diminish the bearing capacity and enlarge the deformation of structures (Sakr and Sakla, 2008).It would also cause nonlinear response of composite structures (Soty and Shima, 2013). It is valuable and necessary to measure the interfacial states of composite structures in order to evaluate the structure performance (Chen and Shi, 2011).However, it still remains difficulty to measure the interfacial slip and uplift quantitatively either in practical application or in scientific research. This paper introduced fiber Bragg grating sensors, known as FBG sensors shortly, to study the nonlinear behavior ofsteel-concrete composite structures. FBG sensor is a kind of optical fiber sensor which was studied by Hill et al. (1978) firstly and introduced to civil engineering by Prohaska et al. (1993). The applications of FBG sensors in concrete structures and steel structures were reported by Chung and Kang (2008) and Rodrigues et al. (2012), respectively. The research of Kesavan et al. (2010) showed that the FBG sensor was sensitive to the variety of structural states and has much less influence to structure than the conventional strain gauges.Despite the investigations of FBG sensor in civil engineering, the application in composite structures is very rare. In the work of this paper, a series of FBG sensors were designed and arranged in a steel-concrete composite deck specimen. The composite deck was designed based on a real bridge. Concrete cracks, interfacial slip and uplift were studied. Meanwhile, additional measurement using conventional strain gauges was settled to make comparisons. Results of deflection, slip, uplift and crack are illustrated and analyzed. 2.PRINCIPLE OFOPTICAL FBGAn optical FBG is made by exposing optical fibers to an intense UV light. Periodic alterations are formed on the core of optical fibers which make the FBG only reflect particular narrowband lig...