Abstract
In proof-loading of concrete slab bridges, advanced monitoring methods are required for identification of stop criteria. In this study, Two-Dimensional Digital Image Correlation (2D DIC) is investigated as one of the governing measurement methods for crack detection and evaluation. The investigations are deemed to provide valuable information about DIC capabilities under different environmental conditions and to evaluate the capabilities in relation to stop criterion verifications. Three Overturned T-beam (OT) Reinforced Concrete (RC) slabs are used for the assessment. Of these, two are in situ strips (0.55 × 3.6 × 9.0 m) cut from a full-scale OT-slab bridge with a span of 9 m and one is a downscaled slab tested under laboratory conditions (0.37 × 1.7 × 8.4 m). The 2D DIC results includes full-field plots, investigation of the time of crack detection and monitoring of crack widths. Grey-level transformation was used for the in situ tests to ensure sufficient readability and results comparable to the laboratory test. Crack initiation for the laboratory test (with speckle pattern) and in situ tests (plain concrete surface) were detected at intervals of approximately 0.1 mm to 0.3 mm and 0.2 mm to 0.3 mm, respectively. Consequently, the paper evaluates a more qualitative approach to DIC test results, where crack indications and crack detection can be used as a stop criterion. It was furthermore identified that crack initiation was reached at high load levels, implying the importance of a target load.
Highlights
The scope of this paper is to investigate the capabilities of 2D DIC as a method to situ test may be prone to premature termination
To evaluate crack initiation threshold in situ and compare these to results gained in Overturned T-beam (OT)-beams and net reinforcement was placed in the top of the slab
This paper considers the use of 2D DIC for crack identification and evaluation in proofload testing
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The combined effect of these parameters is deemed to significantly influence the structural response and the theoretical predictions. Another challenge related to such evaluations is that the desired outcome might not be reached within the available time and economy. In situ full-scale test methods (proof-loading, diagnostic-loading, failure-loading) have gained interest as a competing method for structural capacity evaluation [1,2,3,4]. When applying in situ full-scale test methods, it can be difficult to identify the unique contribution from specific parameters to the structural response. It is seen that in situ test methods differ significantly, which is reflected in the related monitoring approaches and schemes as well [2]
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