General Design Assumptions for Engineered Cementitious Composites

The use of Engineered Cementitious Composites (ECC) for structural design requires a number of assumptions of the material, some of which can be drastically different from those suitable for normal concrete and tension-softening fiber reinforced concrete. This contribution focuses on design assumptions of the constitutive models of ECC in tension and compression. Specifically, while the tensile strength of the concrete is typically neglected in axial and flexural calculations of reinforced concrete, the tensile load carrying capability of ECC during inelastic straining is explicitly accounted for. Assumptions regarding the shape of the tensile stress-strain relation, usable tensile and compressive strains, and bond between steel reinforcement and ECC will be addressed. In addition, assumptions concerning crack width with respect to serviceablilty limit states will also be discussed. Application of these design assumptions in reinforced flexural ECC elements will be used to illustrate the differences between R/C and R/ECC design. For this purpose, an ECC link-slab designed for combined axial tension and flexure will serve as a case study.