Fiber Bragg grating（FBG） sensors present a great deal of potential in monitoring the structural due to their advantages such as immunity to electromagnetic interference

light weight

small size

multiplexing capabilities

ease of installation and durability.In this paper

the sensing principle is explained at first

and the strain transferring character is conducted in the calibration experiment on the steel plate using universal testing machine

then the research work focus on the dynamic strain measurement and natural frequencies of a steel frame with three stories using a FBG sensing system through experimental and numerical calculation.Two FBG strain sensors were designed and mounted on the steel frame. In a series of impact loading experiments

the data measured by FBG sensors were collected throughout a commercial FBG wavelength interrogation system.The comparison of experimental and numerical results revealed that the FBG sensors have ability of measurement of the dynamic strain of the steel frame structure in real time.