Strong discontinuities, mixed finite element formulations and localized strain injections, in fracture modeling of quasi-brittle materials

J. OLIVER, IVO F. DIAS, A.E. HUESPE

Rohrmoos

Congreso; Euro-C 2010, Computational Modelling of Concrete Structure; 2010

The presented work explores a combination of strain localization methods and strong discontinuityapproaches to remove the flaws (stress-locking and mesh bias dependence) of the classical strainlocalization methods, and reduce the sophistication of the strong-discontinuity based methods. The concept ofstrong discontinuity is initially substituted by that of weak discontinuity capturing the displacement jumpthrough its distribution (smearing) in a finite length: the oriented with of a finite element through which thefracture passes in a rather diffuse manner. In other words, the classical strain localization concept is broughtto the approach, no strong discontinuity enrichment is made and standard constitutive models are used in aclassical strain localization setting. The standard mesh refinement recovers the strong discontinuity conceptby taking the element width to zero. However, in order to remove the spurious mesh orientation dependence,in a second stage specific localization modes are injected, via mixed finite elements formulations, to the pathof elements that are going to capture the cracks. These modes, as well as their injection time, are characterizedfrom the information provided by the SDA. Then, the obtained approach enjoys the benefits of the strong discontinuitiesone, at a complexity similar to the classical, and simpler, localization methods.