engleski

NACFaIL - Numerical Analysis of Concrete Failure Under Impact Loadings

NACFaIL is a program code developed to study consequence of impact loadings on concrete structures. The theoretical framework on which the program is based is continuum mechanics and irreversible thermodynamics. The spatial and temporal distribution of relevant tensor fields (stress and strain) is determinate by numerical integration of the resulting governing equations. For this purpose a finite element method is used to perform the spatial discretization (linear tetrahedral elements) and the finite difference method is used to perform the temporal discretization (explicit time integration). The quantitative description of expected finite strains is conducted according to the Update Lagrange formulation. To account for cracking and damage phenomena, the analyzed concrete structure is modeled by the rate sensitive microplane model with relaxed kinematic constraint (co-rotational formulation). Damage and cracking phenomena are modeled within the concept of smeared cracks. To assure objectivity of the analysis with respect to the size of the finite elements, crack band method is implemented. The contact-impact analysis is based on the mechanical interaction between two bodies (master/slave approach). The contact constrains are satisfied by Lagrange multiplier method (adapted for the explicit time integration). The frictional behaviour on the contact interface is assumed to be of kinematic type and described with the Coulomb friction model. At the level of numerical implementation, the dissipative nature of friction forces is introduced via the relaxation of tangential displacement on the contact interface.

adaptive meshing; concrete; contact/impact loading; explicit time integration; finite elements; microplane model; numerical analysis; strain rate

The program is written in FORTRAN95 and depending on the requirements of the industry ; it can be adapted for other uses and upgraded with new features.