Automated quality assessment of precast girders and estimating optimal placements of deck slabs using 3D laser scanning

Abstract

Many bridges have been constructed using precast components since they offer faster production, lower cost, and more efficient construction compared to conventional in-situ construction. For coupled behavior of precast bridge deck slabs and precast girders, shear pockets on the deck slabs and shear connectors on the girders need to be properly connected. However, precast girders can be easily deformed once they are placed in-situ because of their heavy weights, creeping, tensioning, temperature, etc. Once the girders are deformed, shear pockets and shear connectors may no longer match properly and this mismatch negatively affects the structure performance and safety. To ensure the performance and structural safety of precast bridges, quality assessment of precast girders should be conducted and mismatched shear connectors must be properly replaced or repaired before the installation of precast bridge deck slabs on the precast girders. However, there is neither any method nor study to inspect quality of precast girders and identify mismatched shear connectors after the manufacture of precast girders. In addition, no study has been investigated for reducing the mismatched shear connectors by finding optimal placements of precast bridge deck slabs. Therefore, this study proposes following techniques which can automatically (1) inspect quality of precast girders using 3D laser scanning, (2) estimate the optimal placements of precast bridge deck slabs with respect to precast bridges, and (3) identify mismatches between shear connectors and shear pockets. The proposed technique firstly performs a scan on precast girders using a 3D laser scanner. Then, unnecessary noise data are removed and the coordinate of the scan data is transformed with respect to shape of the precast girder. Afterwards, shear connectors and girder planes are identified from the scan data. Next, quality of the shear connectors and girder planes are assessed and locations of the shear connectors on the precast girders are estimated. Finally, precast bridge deck slabs are optimally placed on the precast girders to minimize the mismatches. To validate the effectiveness of the proposed technique, experiments were conducted on small-scale test specimens and on a real precast girder. The experimental results demonstrated that the proposed technique can accurately assess the quality of precast girders and efficiently estimate the optimal placements of precast bridge deck slabs with respect to precast girders.