Abstract
This paper proposes a static stress estimation method for concrete structures, using the stress relaxation method (SRM) in conjunction with digital image correlation (DIC). The proposed method initially requires a small hole to be drilled in the concrete surface to induce stress relaxation around the hole and, consequently, a displacement field. DIC measures this displacement field by comparing digital images taken before and after the hole-drilling. The stress level in the concrete structure is then determined by solving an optimization problem, designed to minimize the difference between the displacement fields from DIC and the one from a numerical model. Compared to the pointwise measurements by strain gauges, the full-field displacement obtained by DIC provides a larger amount of data, leading to a more accurate estimation. Our theoretical results were experimentally validated using concrete specimens, demonstrating the efficacy of the proposed method.
Highlights
In full-scale civil engineering structures, the actual stress distribution due to self-weight and external loads allows a better understanding of the current structural status
This study presented a uniaxial static stress estimation technique, which combines digital image correlation (DIC) and the stress relaxation method (SRM)
The static stress in concrete structures can be released through the hole-drilling method
Summary
In full-scale civil engineering structures, the actual stress distribution due to self-weight and external loads allows a better understanding of the current structural status. The size of the cores used for the SRM varied between 50 mm and 150 mm [7,8,9]; these holes can potentially behave as structural defects and are not desired in practice Another issue regarding previous studies is that insufficient information was collected about the deformation using the strain gauges. The proposed method initially measures the displacement field around a small drilled hole using DIC; this measurement is subsequently used to estimate the current stress level in the concrete structure by comparing the measured displacement field to that from a finite element model. DIC provides a full-field displacement at all points around the hole, which allows the collection of sufficient displacement information and an effective reduction in the measurement errors caused by the large uncertainty in concrete. The proposed method was validated through laboratory-scale experiments performed on concrete specimens
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