Analytical models for assessment of the safety of multi-span steel beams based on average strains from long gage optic sensors

In structural health monitoring, the safety of a multi-span steel beam is assessed by a comparison between the maximum stress measured during monitoring and the allowable stress of the beam calculated by a design code. The locations and magnitudes of the maximum stress to be monitored keep changing since multi-span beams in buildings and infrastructures are actually subjected to physical loads that have variable positions as well as variable magnitudes. However, most fiber optic sensors measuring the strain only at a local or specified point of a beam cannot consider the variations in the positions of applied loads. Long gage fiber optic sensors that measure average or integrated strain over a relatively long length can consider the variations in magnitudes and positions. On the other hand, the maximum strain in a beam cannot be measured with long gage optic sensors. Therefore, in this paper, analytical models are presented for estimation of the maximum values of strains or stresses in multi-span beams based on the average strains measured by long gage optic sensors. The model was tested in an experiment by comparing the maximum strains directly obtained from electrical gages and the estimated maximum strains from long gage optic sensors.