Local bearing capacity of steel fiber and spirals reinforced UHPC-CA: Mechanism analysis and calculation method

Introducing appropriate coarse aggregate (CA) into ultra-high performance concrete (UHPC) can reduce costs and mitigate early cracking risks, while maintaining mechanical and durability properties. Ultra-high performance concrete with coarse aggregate (UHPC-CA) can demonstrate significant potential for transforming the construction industry. To investigate the local compression behaviors and failure mechanism of UHPC-CA, 9 specimens confined with spirals and steel fibers were tested under local loading conditions. The study focused on load response, failure mechanisms, cracking characteristics, and the relationship between local load and spiral strain. The wedge cleaving theory governed the failure mechanism of UHPC-CA, conceptualized as an arch structure with multiple tie rods under spiral confinement. The study identified two primary failure modes: splitting tensile failure and wedge shear failure, influenced by the middle and top bursting forces. Additionally, the parameter analysis was conducted, leading to the development and verification of a bearing capacity calculation model applicable to UHPC-CA with spirals.