Depth estimation of surface-opening crack in concrete beams using impact-echo and non-contact video-based methods

Abstract

Surface-opening crack is one of the main defects in concrete bridges, which results in degradation in the loadcarrying capacity of these structures. Thus, estimating the depth of such surface-opening crack is vital. This study presents impact-echo (IE) and non-contact video-based methods to estimate the surface-opening crack of concrete beams in the laboratory, and the results are compared with visual inspection. Results show that the IE method estimates a considerably larger crack depth than the non-contact video-based method and visual inspection. Although the difference between the depth measured by non-contact video-based method and visual inspection is small, the depth estimated by non-contact video-based method is slightly larger than that measured by visual inspection because it can identify the unrecognizable micro-crack by visual inspection. Moreover, when adopting the IE method, the depth of inclined crack is more overestimated than the vertical crack.

Nondestructive Condition Assessment of Concrete Slabs with Artificial Defects Using Wireless Impact Echo

“…The shortest path the stress wave generated at the point of impact can follow to reach the other side is passing through the tip of the crack (Figure 2.16). Based on that reasoning, Equation 2.6 can be used to calculate crack depth: (Lin and Su 1997) Where: 𝐻 is the distance between the impact and the crack 𝐻 is the distance between the second sensor and the crack 𝐶 is the travel velocity of the P-wave ∆𝑡 is the travel time between the impact and the sensor 2 The typical Impact Echo result in this case would appear similar to that shown in Figure 2.17 (Sun, et al 2018). This method utilizes the untransformed readings of the sensor in the time domain.…”

“…Ottawa, September 2020 (Sun, et al 2018) ................... Figure 2.17 Typical recorded waveforms showing P-wave arrivals (Sun, et al 2018)…”

“…Figure 2.17 Typical recorded waveforms showing P-wave arrivals (Sun, et al 2018) Based on the results shown in Figure 2.17, ∆𝑡 consist of two portions, an original time where the wave travels to the first sensor as well as the difference between the start of the reading of the first sensor and the second.…”

“…Figure 2.15 Thickness and Flexural Vibration Modes (Carino, 2015) .......................................................................... Figure 2.16 Schematic of testing configuration for estimating the depth of the crack(Sun, et al 2018) ................... Figure2.17 Typical recorded waveforms showing P-wave arrivals(Sun, et al 2018) ................................................. Figure 2.18 Placement sketch (Lin & Su, 1997) ...........................................................................................................…”

“…Figure 2.16 Schematic of testing configuration for estimating the depth of the crack(Sun, et al 2018) …”