Experimental and modeling study of double-layered UHPFRC under bending

Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) is a material characterized by very high compressive strength, excellent durability and damage tolerance. For a UHPFRC beam works under bending, steel fibers distributed in the beam compressive zone has insignificant effects on the improvement of its flexural capacity. To use the fibers more efficiently, this paper applies the concept of layered-structure to UHPFRC beam. A double-layered UHPFRC beam composed of a top plain UHPC layer and a bottom UHPFRC layer containing 2% steel fibers is designed. In the experimental section, basic mechanical properties of the individual UHPC and UHPFRC layers are investigated. Compression, split tension and bending tests are conducted, the results of which provide input parameters and model validation for the simulation section. The effects of layer thickness on the beam flexural properties and stress distributions are analyzed numerically with the validated model, and the results show that the peak flexural load and the energy increase with the increase of the UHPFRC layer thickness. Results from this study shed lights on the design of layered UHPFRC structures, and contribute to the application of layered UHPFRC in engineering constructions