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In-situ stress identification of bridge concrete components using core-drilling method

Concrete components of existing bridges often have complex and time-dependent stresses due to external load and internal degradation. The reliable information of the stress state plays an important role in performance assessment, life cycle prediction and strengthening and maintenance strategy. Some key bridge components generally carry predominant uniaxial loads, such as girders, towers and pillars, which make it meaningful to focus on the uniaxial in-situ stresses. This article presents a non-destructive method to identify the uniaxial in-situ stresses in concrete components for existing bridges using core-drilling method based on influence functions (IFs). Axial and tangential IFs are defined and calibrated, followed by numerical identifications of different stress fields and experimental tests on concrete specimens. The influence of inhomogeneity and randomness of concrete in the identification tests are evaluated by comparisons of measured data from various strain gages and reduced by introduction of interpolation functions, synthetical IFs and optimisation solutions. The relationship between identification accuracy and damage cost is also investigated.