Development of Innovative Perforated and Confined Compression Cast Concrete (PC-CCC) for FRP-Reinforced Compression Yielding (CY) Beam

Fibre-reinforced polymer (FRP)-reinforced concrete beams have attracted research interest due to the advantages of FRP such as high tensile strength and excellent corrosion resistance. However, the non-ductile behaviour of FRP leads to brittle failure of FRP-reinforced concrete beams. To address this issue, an innovative concept of compression yield (CY) beams was developed. The principle of CY beams is to replace the concrete on the compression side of the plastic hinge region in FRP-reinforced concrete beams with a highly ductile material, called CY material. Through this method, the CY material undergoes compressive yielding to produce significant ductile deformation, and the plastic hinge zone undergoes significant deformation, resulting in significant bending deformation of the beam. Previous experimental studies on CY beams have shown that this approach can result in beams with adequate ductility; however, CY beams also exhibit insufficient rigidity under service loads. This problem is caused by the insufficient elastic modulus of the CY material used, which is significantly lower than that of normal concrete. Therefore, it is required to develop a new CY material with both high ductility and sufficient elastic modulus to solve the issue of insufficient rigidity of CY beams.

In this project, a new CY material, perforated and confined compression cast concrete (PC-CCC), is developed through multiple trials. This study outlines the design details and manufacturing process of PC-CCC, and investigates the axial stress-strain behaviour and some important mechanical properties. The experimental results show that PC-CCC can meet the requirements of elastic modulus and ductility simultaneously. Models for the relationships between PC-CCC material design parameters and key mechanical properties are proposed and validated. Using the proposed models, the material design parameters of PC-CCC can be predicted with specific mechanical properties through optimal design, thereby guiding the design of PC-CCC.

In addition, a new CY beam with PC-CCC is designed. An FE model of the new CY beam is developed and validated. A parametric study is conducted through numerical simulation to discuss the effects of the key mechanical properties of PC-CCC on the CY beams. The results indicate that the CY beams with PC-CCC can meet the rigidity requirement under service loads. In qualitative analysis, the results show that the properties of CY beams are most affected by the relevant PC-CCC mechanical properties, and it provides the general design principle of CY beams. This study also introduces a model for the ductility of the CY beams and proposed a model for the loading capacity of the CY beams. Both models are validated through numerical simulation results, which show that both models can accurately predict the performance of the CY beams and assist in the design of the CY beams.