Condition Assessment of Metsimotlhabe River Bridge using Non-Destructive Testing and Non-Contact Procedure

A process of in-service infrastructure health assessment using non-destructive testing and evaluation (NDT&E) techniques is crucial for prompt, accurate and quantitative identification of damage in civil infrastructure. The aim of this study was to assess the structural performance of Metsimotlhabe River Bridge through NDT&E and load testing techniques. Schmidt rebound hammer was utilized to determine the compressive strength of the bridge, total station was used to monitor the profile of the bridge girder level for differential deformation, and a non-contact global positioning system (GPS) technology was employed to measure the dynamic displacement of the bridge under random operational traffic loading conditions. Finally, the dynamic behavior of the bridge was evaluated based on displacement, strain and acceleration response data. There was a perfect linear correlation between rebound number and compressive strength of concrete from different contact surfaces. The compressive strength of the bridge superstructure from random sampling was 39.48 N/mm2 (CoV = 19.22%). The normal distribution of the bridge levels at the northern and southern levels depicted differential displacement that indicated torsional deformation. The displacement of the bridge girder was simultaneously monitored at the supports, quarter-spans and mid-span using GPS technology. The results showed functional elastomeric bearings at the supports, perfect correlation at the quarter spans and maximum dynamic flexural displacement of 21.5 mm at the mid-span. The modal decomposition acceleration and displacement response data produced the first three flexural modal frequencies of 6.44 Hz, 9.10 Hz and 19.56 Hz. It can be concluded that while the bridge was in good condition in terms of its compressive strength, elastomeric bearings and fibre strain, the differential displacement at the northern-southern edges of the bridge was a clear indication of torsional deformation of the superstructure.