Investigations of Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) Column

Abstract

Ultra-high-performance concrete (UHPC) has attracted significant attention in recent decades due to its superior compressive strength and exceptional durability, while concerns have been raised due to the fact that inherent brittleness of concrete resulted in an explosive failure of UHPC. To extend the applications of UHPC in engineering design and construction, incorporating randomly distributed steel fibres into UHPC concrete matrix has been considered as one of the effective methods to enhance the ductility of the material. This is due to the fibre bridging effects preventing the propagation of the crack thereby to enhance the ductility and compressive and tensile strengths of the material. Therefore, the ultra-high performance fibre reinforced concrete (UHPFRC) has a great potential to bring a step-change in the way of infrastructure are designed and constructed. The main objectives and findings of this paper are detailed as follows: (1) To study the long-term shrinkage mechanisms of UHPC with and without steel fibres, a series of experiments was conducted to achieve the optimal mixtures with the autogenous and drying shrinkage mitigated. (2) To investigate the structural responses of axial members (both UHPFRC short and slender columns) subjected to a concentric or eccentric load, the optimal UHPFRC mixture was then utilized to manufacture the test specimens for experimental investigations. (3) A generic mechanic-based partial-interaction (PI) approach that used to simulate the conventional concrete members (flexural and axial members) is suitably modified based on the material properties of UHPFRC to accurately simulate the structural responses of the short UHPRC columns under eccentric loading conditions. (4) Finite element analysis (FEA) is carried on in conjunction with a concrete damage plasticity (CDP) model to simulate the structural behaviours and damage patterns of both UHPFRC short and slender columns subjected to a concentric or eccentric load. An extended study is also conducted based on the clarified finite element (FE) model to investigate the slenderness effects regarding the structural response of the slender columns. (5) An experimental program is undertaken to investigate the structural performances of the concrete-filled carbon FRP tube (CFRP-CFFT) columns manufactured with ultra-high-performance fibre reinforced concrete (UHPFRC). Furthermore, finite element (FE) analysis incorporating CDP and Hashin’s damage model is then conducted to simulate both the structural response of CFRP-CFFT UHPFRC columns as well as the corresponding damage patterns of CFRP tubes and concrete. The proposed load-moment (P-M) interaction envelopes regarding UHPFRC short and slender columns as well as CFRP-CFFT UHPFRC column generated in these studies accurately predict the structural behaviours of columns subjected to axial loads with different eccentricities. Hence, these P-M envelopes can serve as foundations for promoting design guideline of the UHPFRC columns in the future.