Qingduo Hao

Experimental testing of a self-sensing FRP-concrete composite beam using FBG sensors

A new kind of self-sensing fiber reinforced polymer (FRP)-concrete composite beam, which consists of a FRP box beam combined with a thin layer of concrete in the compression zone, was developed by using two embedded FBG sensors in the top and bottom flanges of FRP box beam at mid-span section along longitudinal direction, respectively. The flexural behavior of the proposed self-sensing FRP-concrete composite beam was experimentally studied in four-point bending. The longitudinal strains of the composite beam were recorded using the embedded FBG sensors as well as the surfacebonded electric resistance strain gauges. Test results indicate that the FBG sensors can faithfully record the longitudinal strain of the composite beam in tension at bottom flange of the FRP box beam or in compression at top flange over the entire load range, as compared with the surface-bonded strain gauges. The proposed self-sensing FRP-concrete composite beam can monitor its longitudinal strains in serviceability limit state as well as in strength limit state, and will has wide applications for long-term monitoring in civil engineering.

Experimental investigation of smart FRP-concrete composite beam with embedded FBG sensors

Fiber Bragg grating (FBG) sensor is broadly accepted as a structural health monitoring device for fiber reinforced polymer (FRP) materials by either embedding into or bonding onto the structures. A new kind of smart FRP-concrete composite beam was developed by using embedded FBG sensors. Firstly, fabrication process of the smart FRP-concrete composite beam was introduced. Subsequently, FRP laminates with embedded FBG sensors, which have the same stacking sequences as that of the smart composite beam, were fabricated and tested on material test system to determine the strain sensitivity coefficients of the smart composite beams. Finally, the proposed smart FRP-concrete composite beam was tested in 4-point bending to verify the operation of FBG sensors embedded in the smart beam. The experimental results indicate the strain sensing property of the laminates with embedding FBG sensors is nearly the same as that of bare FBG sensor, and the output of embedded FBG sensors in the smart beam agrees well with that of surface-bonded strain gauges over the entire load range. The proposed smart FRP-concrete composite beam can reveal the true internal strain of itself in its service life and will have wide applications for long-term monitoring in civil engineering.

Development Length of Glass Fiber Reinforced Plastic (GFRP)/Steel Wire Composite Rebar

The bond between glass fiber reinforced plastic (GFRP)/steel wire composite rebars and concrete is the key problem to the performance of concrete structures reinforced with GFRP/steel wire composite rebars. In this study, pull-out test was tested to experimentally investigate the bond strength of GFRP/steel wire composite rebars to concrete. The test variables were the nominal diameter, the embedded length, the concrete compressive strength, the concrete cover thickness and the concrete cast depth. Based on the two modification factors of 1.2 and 1.6 to account for the top rebar effect and concrete cover effect, respectively, a new formula is proposed for the calculation of development length for GFRP/steel wire composite rebars.

A Smart FRP-Concrete Composite Beam Using FBG Sensors

A new kind of smart FRP-concrete composite beam, which consists of a FRP box beam combined with a thin layer of concrete in the compression zone, was developed by using two embedded FBG sensors. The fabrication process of the smart FRP-concrete composite beam was introduced. The proposed smart composite beam was tested in 4-point bending to verify the operation of the embedded FBG sensors. The experimental results indicate the output of embedded FBG sensors in the smart beam agrees well with that of surface-bonded strain gauges over the entire load range. The proposed smart FRP-concrete composite beam can reveal the true internal strain from 0 to the failure of the beam and will have wide applications for long-term monitoring in civil engineering.

Experimental testing of a smart FRP-concrete composite bridge superstructure

A new kind of smart fiber reinforced polymer (FRP)-concrete composite bridge superstructure, which consists of two bridge decks and each bridge deck is comprised of four FRP box sections combined with a thin layer of concrete in the compression zone, was developed by using eight embedded FBG sensors in the top and bottom flanges of the FRP box sections at mid-span section of one bridge deck along longitudinal direction, respectively. The flexural behavior of the proposed smart composite bridge superstructure was experimentally studied in four-point loading. The longitudinal strains of the composite bridge superstructure were recorded using the embedded FBG sensors as well as the surfacebonded electric resistance strain gauges. Test results indicate that the FBG sensors can faithfully record the longitudinal strain of the composite bridge superstructure in tension at bottom flange of the FRP box sections or in compression at top flange over the entire loading range, as compared with the surface-bonded strain gauges. The proposed smart FRPconcrete composite bridge superstructure can monitor its longitudinal strains in serviceability limit state as well as in strength limit state, and will has wide applications for long-term monitoring in civil engineering.