Shear capacity of innovative hybrid concrete structures with SHCC lamellas applied laterally

Abstract

Strain Hardening Cementitious Composite (SHCC) is an innovative type of fibre-reinforced cement-based composite that has superior tensile properties. Because of this, it holds the potential to enhance the shear capacity of reinforced concrete (RC) beams, if applied properly.

Experimental research was thus carried out with the purpose of investigating the shear behaviour of reinforced concrete beams enhanced with thin SHCC laminates (10 mm in thickness) in their webs (henceforth referred to as hybrid SHCC-concrete beams). This research distinguishes itself from other studies by the fact that the hybrid beams were manufactured by casting conventional concrete inside pre-cast SHCC laminates, consequently, forming an interface between concrete and SHCC. Moreover, two different types of SHCC-concrete interface designs have been used in the hybrid beams, namely smooth and profiled ones. Furthermore, beams with and without transverse reinforcement (stirrups) were both prepared in order to investigate the effect of two specific methods of shear reinforcing (i.e., SHCC and stirrups) on each other. On top of that, one of the hybrid beams with stirrups has been supported only at its normal concrete core to uncover any irregularities in the shear behaviour compared to a beam supported at its full-width. Conventional RC beams (without SHCC laminates) were also prepared as references. All beams were tested in a three-point bonding set-up while monitored by two separate systems: Digital Image Correlation (DIC) and Linear Variable Data Transformers (LVDTs). The camera images were analysed by the software package, GOM Correlate 2019. During the casting of the beams, samples of all materials were taken and tested to establish their mechanical properties for quality control purposes.

Results show that the hybrid beams have obtained higher shear capacity than the control group. Only the hybrid beams with a minimum amount of shear reinforcement were capable to activate SHCC web laminates to their full extent. In the case of hybrid beams without transverse reinforcement (TR), only half of SHCC laminate potential was utilised approximately.

This study proves that, by applying advanced material (i.e., SHCC) properly, an efficient way of improving the shear capacity of an RC beam can be achieved, so long there is minimum TR provided. If a minimum transverse reinforcement is not present, the benefits of shear enhancement by SHCC become less effective due to the low Young’s modulus of SHCC.