A distributed Brillouin fiber sensor was used to monitor the health of steel structures. We used this method on two steel beam specimens and longitudinal strain and cracks were detected well under different loads. The difference between the longitudinal strain measured by the distributed fiber sensor and that measured by strain gages is less than 4%. Traditional sensors or transducers that measure the average strain over a small region always miss cracks. The method proposed in this study gives very good results for the detection of cracks and the surrounding strain on a square pipe.
