Fig. 1. Fiber Bragg grating strain sensor encapsulated in stainless steel tube. (a) Basic structure; (b) Physical image of sensor

Fig. 2. Comparison between long gauge FBG and strain gauge

Fig. 3. Four point symmetrical loading of simply supported box girder. (a) Four point symmetrical loading diagram; (b) Section dimensions and layout of measuring points for steel box girders

Fig. 4. Finite element simulation load deformation of steel box beam

Fig. 5. Four point symmetrical loading of simply supported box girder. (a) Four point symmetrical loading comparison; (b) Four point symmetrical loading error

Fig. 6. Deflection measurement experiment of simply supported box girder

Fig. 7. Loading and sensor layout of simply supported box girder

Fig. 8. Response of steel box girder under different levels of loading at mid span. (a) Strain response; (b) Deflection inversion

Fig. 9. Comparison of displacement monitoring results and theoretical values under different grades of loads

Fig. 10. The variation of measured mid span deflection and mid span strain with load level. (a) Measured displacement using a mid span dial gauge; (b) Measured strain of mid span unit

Fig. 11. Measured mid-span deflection and mid-span strain vary with load level. (a) Displacement of loading point 1 under different loads;(b) Displacement of loading point 2 under different loads; (c) Displacement of loading point 3 under different loads