397 ACI Structural Journal/May-June 2015 ACI STRUCTURAL JOURNAL TECHNICAL PAPER Damage and loss assessment of reinforced concrete elements are based in part on the length, width, and areal density of cracks. Crack information is traditionally collected using a crack width card and transferred to drawing sheets, which is both approximate and labor-intensive. An automated procedure involving digital image processing was developed and deployed to collect and process crack data. The procedure was developed and validated using data from the cyclic testing of nine reinforced concrete shear walls of varying aspect and reinforcement ratios. Keywords: automated crack detection and measurement; damage assess- ment; imaging. INTRODUCTION The length, width, and areal density of cracks are used for damage assessment of reinforced concrete compo- nents in the laboratory and in the ield. Damage to rein- forced concrete components in buildings and infrastructure after earthquake shaking is often inferred using maximum residual crack widths. Strategies for post-earthquake repair are often based on this information. Cracking of reinforced concrete components during laboratory testing is routinely documented (along with other information) to enable a reconciliation of loss of strength and stiffness with observed damage. Information on the cracking of low aspect-ratio reinforced concrete shear walls 1 has been used to generate fragility functions and consequence functions that enable an estimate of the repair cost per unit area of wall. Engineers have traditionally identiied cracks visually in reinforced concrete components, measuring their widths using a crack-width card and then transferring that data to drawing sheets. Crack width is measured either at user- determined locations along the length of a crack, or a maximum crack width is reported. Cracks are assigned a width equal to one of the marks on the gauge (for example, 0.005 in., 0.016 in., or 0.06 in.; refer to Fig. 1). Widths of cracks between the marks on a gauge can only be estimated. The process is laborious and approximate because uncer- tainty is introduced in the measurement of the crack width, the use of few measurement locations, and the transfer of information to drawing sheets. Imaging tools provide a means to improve the process of measuring and documenting cracks and their widths, and to substantially improve the quality and accuracy of the results. Noncontact identiication and measurements of cracks enables data to be gathered from large-size labora- tory tests at instances of peak loading and deformation in a safer and more reliable manner. Gathering information on the length, width, and areal density of cracks at instances of peak deformation and zero loading enables estimates to be made of structural damage to components, which are better correlated with peak transient crack widths and lengths than residual crack widths and lengths. An automated process for detecting cracks, and measuring their widths and lengths is presented in this paper. Data from the tests of nine large-size, low aspect-ratio rein- forced concrete shear walls are used to develop and vali- date the algorithms and computer codes. The algorithms, source code, and documentation will be uploaded to NEEShub (www.neeshub.org) for use by researchers and forensic engineers. RESEARCH SIGNIFICANCE An automated, noncontact procedure is proposed for the estimation of crack width, length, and areal density. The proposed procedure, which could be used in the ield and the laboratory, is safer, faster, and more accurate than the tradi- tional method of measuring lengths and widths of cracks by hand using crack gauges and tapes and then transferring that information to drawing sheets. LITERATURE REVIEW Image-based crack-detection algorithms have been used primarily to detect cracks on pavement surfaces. Most crack-detection algorithms rely on edge detectors to locate Title No. 112-S32 Automated Detection and Measurement of Cracks in Reinforced Concrete Components by Jonathan P. Rivera, Goran Josipovic, Emma Lejeune, Bismarck N. Luna, and Andrew S. Whittaker ACI Structural Journal, V. 112, No. 3, May-June 2015. MS No. S-2014-084.R1, doi: 10.14359/51687424, received August 18, 2014, and reviewed under Institute publication policies. Copyright © 2015, American Concrete Institute. All rights reserved, including the making of copies unless permission is obtained from the copyright proprietors. Pertinent discussion including author’s closure, if any, will be published ten months from this journal’s date if the discussion is received within four months of the paper’s print publication. Fig. 1—Crack gauge. 11 (Note: 1 in. = 25.4 mm.)