Numerical Modelling of the Compressive and Tensile Behavior of Ultra-High Performance Concrete in Beams

Introduction

Ultra-high performance concrete (UHPC) differs in its structural behavior from conventional concrete upon loading due to its high compressive and tensile strength, stiffness, toughness, and durability. Therefore, UHPC needs an appropriate constitutive model to simulate its mechanical properties in finite element analysis (FEA).

Method

In this study, numerical models were developed to trace the structural behavior of UHPC beams upon loading since beam behavior depends on the constituents' response to compression and tension. New numerical models were formulated to display the stress-strain relationships of UHPC in compression and tension by adopting a new methodology that depended on actual results. The compressive stress-strain relationship consisted of two portions; the ascending one for elastic and strain hardening up to compressive strength and a descending curve for the strain-softening until reaching a strain of 0.0062.

Result

A linear tensile stress-strain relation was applied for the elastic tensile behavior up to tensile strength. Then, a tri-linear relationship was applied for the stiffness degradation and crack propagation upon debonding fibers from the concrete matrix until fracture. These numerical models were used in Abaqus software to simulate the UHPC beam behavior.

Conclusion

The developed models were verified and approved for beams' behavior upon loading in flexure and shear. The results indicated that the models could predict the UHPC beams' response throughout the entire loading range from the beginning until failure. The verification included bear capacity, deflection, crack pattern, and stress distribution.