Development of stress block parameters for ultra high performance concrete

Abstract

Extensive literature exists on mix design, production methods, and the structural behavior of ultra-high-performance concrete elements (UHPC). Numerous studies in these domains have significantly contributed to our comprehension of UHPC. Nevertheless, a notable research lacuna persists in formulating rectangular stress block parameters tailored specifically for UHPC. This gap arises from the predominant reliance on prevailing standard codes and guidelines, which are founded on experimental data derived from normal concrete, rendering them inadequately applicable to the design of UHPC structures. This paper addresses this research gap by proposing novel rectangular stress block parameters explicitly designed for UHPC. The compression stress block is derived by modeling the stress–strain response and evaluating the shape factor. Simultaneously, the tension stress block is developed by modeling responses during the linear elastic phase, fiber activation, and fiber activation stages using stress versus crack width relationships. The derived relationships considering strength, reinforcement index, and fiber efficiency satisfactorily predict the moment capacity of UHPC beams with varying fiber dosages and geometrical dimensions. The proposed stress block parameters, denoted as alpha and beta, are presented for compression strength ranging up to 200 MPa and found suitable for designing structural members using UHPC.