| Abstract: |
Ultra-High-Performance Concrete (UHPC) has emerged as a transformative material in modern structural engineering, distinguished by its exceptional compressive strength (exceeding 150 MPa), remarkable ductility, and superior durability characteristics compared to conventional concrete. This review paper presents a comprehensive meta-analysis of existing experimental, analytical, and numerical studies focusing on the structural behavior of UHPC members subjected to combined loading conditions, including flexure-shear, axial-flexure, torsion-flexure, and multi-axial stress states. A systematic examination of over sixty peer-reviewed investigations conducted between 2000 and 2024 reveals consistent trends in failure mode transitions, interaction surface formulations, and ductility enhancement mechanisms attributable to the steel fiber-reinforced microstructure of UHPC. The meta-analysis consolidates data across beam, column, and slab elements to identify critical parameters governing combined load response, including fiber volume fraction, matrix composition, reinforcement ratio, and slenderness effects. Significant discrepancies between current design code provisions and experimentally observed capacities are identified, particularly for shear-dominant combined loading scenarios. The review critically evaluates the adequacy of existing analytical frameworks and proposes directions for more robust interaction surface models. Findings indicate that UHPC members under combined loading exhibit markedly different failure mechanisms than those observed in normal-strength concrete, necessitating revised design philosophies. This paper provides a consolidated reference for researchers and practicing engineers and establishes a foundation for future experimental programs and codification efforts in UHPC structural design. |
