Monitoring of strain profile variations in the RC slab of a short span railway bridge

A novel monitoring scheme oriented towards the structural examination of reinforced concrete slabs subject to railway traffic action is presented. Monitoring is based on the measurement of the mean axial strain profile variation in the cross-section of the slab. The strain profile is reconstructed under the assumption of plane sections by measuring the variation of two distances between two pairs of points materialized at two different levels under the slab on rigid attachments fixed on the slab. The distance variations are measured by means of strain gages measuring the deformation of two very thin strips connecting the two attachments. The implementation of the above scheme on a short-span railway bridge for a period of 7 months and the processing of the acquired signals are presented in detail. Some interesting monitoring records are provided over which the efficiency of the proposed scheme is discussed.