Structural condition assessment of reinforced-concrete bridges based on acoustic emission and strain measurements
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ORIGINAL PAPER
Structural condition assessment of reinforced‑concrete bridges based on acoustic emission and strain measurements Imane Bayane1 · Eugen Brühwiler1 Received: 8 June 2020 / Revised: 17 August 2020 / Accepted: 21 August 2020 © The Author(s) 2020
Abstract A reliable novel monitoring approach is developed to assess the structural condition of reinforced-concrete bridge elements. The approach is based on combining acoustic emission technique and strain gauge measurements, and it is illustrated by a case study of a composite steel–concrete viaduct in service since 1957. Monitoring was performed on its reinforced-concrete deck slab under traffic and environmental loading for one year. The monitoring setup and procedure are presented. The variation of acoustic emission signals is evaluated regarding strain and temperature measurements. Parametric study, pencil-break test, statistical analysis, crack classification and b-value analysis are performed to assess the structural condition. The acoustic emission activity of the reinforced-concrete slab is evaluated for 1 year under operational conditions. From the monitoring approach, it was possible to identify the nature of the cracking activity in the concrete slab as a function of traffic loading and temperature and to assess in time the condition of the slab-girder connection. Keywords Monitoring · Road bridge · Acoustic emission (AE) · Strain measurement · Structural condition · AE feature · Parametric study · b-value analysis · Cracking mode
1 Introduction The sustainable and economical use of existing reinforcedconcrete (RC) bridges requires reliable assessment of their current condition under service loading. For road bridges, RC deck slabs are the most fatigue vulnerable part due to the pronounced effect of vehicle’s axles [1–5]. RC decks often need assessment to meet both the safety and serviceability requirements of infrastructures particularly with the increase of the magnitude and frequency of axle loads. The assessment of RC decks refers to the early stage assessment of concrete and steel reinforcement condition, as well as the bond between them. The effect of cyclic loading on RC structural elements was investigated in [1, 6–10]. However, most of these studies were limited to laboratory testing and only few have performed assessment on real structures. Different NDT methods were used to evaluate bridges on site such as radar, impact echo, and infrared * Imane Bayane [email protected] 1
Laboratory of Maintenance and Safety of Structures (MCS), Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
thermography [11–13]. Such methods allow to detect delamination, moisture, and discontinuities in concrete but are limited for initial microcrack detection. Early stage assessment is often restricted to visual inspections [14–16] that are subjective and not always reliable, or calculations of structural capacity [17], which are very conservative with the unrealistic assumptions and models related to loading and material properties.
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