Assessing steel strains on reinforced concrete members from surface cracking patterns

Abstract

h i g h l i g h t sMethod to assess steel strains inside concrete members using surface measurements. This approach has non-contact and does not interfere with the bond between steel and concrete. Validation using concrete ties monitored using strain gauges placed inside the steel bars. The technique can be applied to narrow regions, surrounding a single crack, or to larger regions. Results proved the feasibility of the method. a b s t r a c tThe measurement of steel strains in reinforced concrete structures is often critical to characterise the stresses along the member. In this scope, this manuscript describes the development of a method to assess steel strains inside concrete members using solely surface measurements. These measurements were obtained using photogrammetry and image processing. The technique was validated using two concrete ties monitored with strain gauges placed inside the steel bars. The experimental results showed that one of the most important parameters affecting the accuracy of the technique is the measurement of crack widths. In comparison, the concrete strain has little effect on the final results. The technique is particularly advantageous since it is non-contact and does not impact on the bond conditions. It also does not require accessing the reinforcements. As a main conclusion, this work showed the feasibility of estimating strains inside the structure using surface measurements. This technique will benefit in the near future from further improvements namely in what concerns the camera resolution.

A new method for corrosion assessment of reinforcing bars based on close‐range photogrammetry: Experimental validation

“…[40][41][42][43] Several potentially new interesting applications of this technique to tackle problems in civil engineering have been presented. 44,45 These applications can take advantage of the commercial software available, provided that control parameters, which guarantee the quality of the data obtained, are evaluated, namely: ratio between distance-to-object and focal length; the sensor size; the number and location of the camera station; and the exposure of the camera (i.e., the relationship between aperture, shutter speed and ISO). 14 Thus, 3D models of an object can be computed using a multistation network configuration for image acquisition, follow-on higher precision photogrammetric projects and a suitable 3D model.…”

Evaluation of the shear transfer mechanisms in reinforced concrete beams using photogrammetry

“…Later, developments were settled for assessment displacements during load tests . Then, methods to compute displacement and strain fields on surfaces were developed and successfully applied to monitoring experimental tests . Depending on the case, the methods were customized to compute all relevant physical parameters required for structural analysis.…”

“…Those methods, based on photogrammetry and image processing, were used to monitoring reinforced concrete (RC) members: measurement of displacements; evaluation of strain field; and detection and characterization of cracks . Based on the data recorded, several structural parameters can be assessed, such as: deflection; curvature and rotation; load path; and steel strain estimation . Moreover, the applications already performed in the scope of shear behavior, using photogrammetry, stereo vision, and/or cracking analysis, showed clear advantages over the traditional methods, including concrete members without transverse reinforcement …”

“…[20][21][22][23] Based on the data recorded, several structural parameters can be assessed, such as: deflection 13,16 ; curvature and rotation 24 ; load path 25 ; and steel strain estimation. 26 Moreover, the applications already performed in the scope of shear behavior, using photogrammetry, stereo vision, and/or cracking analysis, showed clear advantages over the traditional methods, 6,[27][28][29][30] including concrete members without transverse reinforcement. 6,27 In this paper, the method Photo-Shear, based on computer photogrammetric vision and tailored postprocessing of data, is presented to evaluate the shear behavior of RC beams.…”

Method for assessing beam column joints in RC structures using photogrammetric computer vision

“…These methods are allowed to measure displacements, evaluate the strain field, and detect and characterise cracks . The complete assessment of the surfaces of concrete members enables to track the evolution of several structural parameters: (a) curvature and rotation of sections; (b) deflection; (c) strain maps; (d) cracks pattern and cracks width; and (e) steel strain estimation . One of the new challenges is focused on improving and developing those tools, to apply not only on members but also on the joints between them, allowing to perform a more detailed and demanding structural analysis.…”