Flexural behaviour and cost effectiveness of layered UHPC-NC composite beams

Abstract

This paper presents a pilot numerical study to investigate the flexural performance of simply-supported layered ultra-high performance concrete (UHPC)-normal strength concrete (NC) beams consisting of two UHPC layers with an NC core layer sandwiched in between. A three-dimensional finite element model (FEM) is developed for the beam and is validated against the existing experimental results of UHPC-NC bi-layer composite beams. The effects of the bonding between UHPC and NC layers, the fraction of UHPC and NC in the beam, and the mechanical properties of UHPC material on the flexural performance of the beam are discussed in detail. Numerical results show that the flexural behavior of the layered UHPC-NC beam is significantly influenced by the interfacial bonding between UHPC and NC layers that is represented by the cohesive stiffness which should be higher than 3 to avoid possible delamination failure in the beam. The material cost effectiveness of the layered UHPC-NC beam is also evaluated. It is found that with properly designed UHPC layer thickness, the beam with a thick NC core layer can not only sustain the same loading as a pure UHPC beam with the same thickness but is also much less costly, indicating the excellent mechanical performance and great cost effectiveness of the proposed layered UHPC-NC beam.