Lateral torsional buckling of ultra-high-performance fibre-reinforced concrete girders

Ultra-high-performance fibre-reinforced concrete (UHPFRC) is a relatively newly developed construction material that not only has high compressive strength (greater than 150 MPa), but also high tensile strength (10-20 MPa). The use of UHPFRC enables the design of slender structural members; hence, instability could become a major governing failure mode. However, the estimation of buckling strength for a concrete structure is not easy, owing to its material characteristics. In this paper, the lateral torsional bucking behaviour and strength of ultra-high-performance concrete I-beams are discussed. A methodology is introduced to obtain the effective moment of inertia of UHPFRC I-beams, considering tensile cracks. By using the effective moment of inertia, the linear elastic buckling strength can be calculated. In addition, the inelastic lateral torsional buckling behaviour is investigated through finite-element analysis. A generalised buckling strength curve with a slenderness parameter is discussed. As a result, the limitations for classification of compact and non-compact members are defined, and lateral torsional buckling strength equations are suggested for a simply supported UHPFRC I-girder subjected to centre point loading. Several experimental studies were also conducted, and the results are applied to verify the final results.