Static and dynamic testing of delamination in hybrid SHCC/concrete beams

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.