Abstract
The focus of this study is to characterize delamination using static and dynamic tests and to assess the interface failure mechanism of an innovative hybrid concrete beam, made out of conventional concrete and a special class of fibre reinforced material, known as Strain Hardening Cementitious Composite (SHCC).Three SHCC beams were subject to four-point bending tests, differing in the interface surface preparation and curing method. Damage and delamination were gradually induced due to increasing loads in steps of 2.5 kN, and their propagation was tracked by the use of linear variable differential transformers and Digital Image Correlation technique. Dynamic hammer tests were also carried out to identify the natural frequency variation due to progressive damage. The outcome of this comparison allowed us to assess the capability of using a frequency-based monitoring technique for possible early-stage delamination detection of hybrid civil structures.To understand the influence of delamination on the dynamic response, a simplified finite element modelling approach of delamination was adopted. The induced damage was modelled in a simplified manner by reducing the stiffness of the elements in the damaged area. This model can be potentially integrable into large-scale numerical models for Structural Health Monitoring purposes.
Highlights
The development of Structural Health Monitoring (SHM) strategies in Civil Engineering is usually driven by the concern of assessing the health condition of existing civil infrastructures [1,2,3]
Composite Structures 281 (2022) 114961 damage. Within this framework and with reference to the information retrieved from the FE models, this study proposes simplified benchmark models that allow to mimic the natural frequency shifts caused by the observed delamination and crack patterns, and that are able to be merged into an eventual vibrationbased damage detection strategy, applicable on large-scale structures composed by means of hybrid structural elements
Von Mises strain is usually used to evaluate the occurrence of yielding in ductile materials, a high concentration of such strains is strongly linked to crack formation and as such, von Mises strains are commonly used in combination with Digital Image Correlation (DIC) to clearly visualize cracks in concrete and masonry structures [39,40]
Summary
The development of Structural Health Monitoring (SHM) strategies in Civil Engineering is usually driven by the concern of assessing the health condition of existing civil infrastructures [1,2,3]. Besides the challenge of assessing existing structures, SHM strategies become even more important for new structures built using novel materials, new structural systems and construction technologies, which are usually accompanied by a lack of experience on their application, lack of design codes and scarce knowledge on the long-term structural behaviour. Examples of new structural systems can be found in the domain of composite and hybrid structures [4,5,6,7,8], for which developing structural safety assessment techniques is of paramount importance due to the rudimentary knowledge of the interface mechanisms governing the debonding and fracture behaviour [9,10]. The existence of a (non-reinforced concreteto-concrete) interface in hybrid structures might trigger brittle failure, which could eventually be detected at an earlier stage by using proper monitoring techniques. Developing monitoring strategies able to timely detect the initiation of a brittle failure is one of the biggest challenges within the SHM community
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