AN EXPLICIT FINITE ELEMENT MODEL FOR FIBER REINFORCED CONCRETE UNDER TRACTION

J. RUBERT; E. B. LAS CASAS; S. OLLER

Congreso; European Congress on Computational Methods in Applied Sciences and Engineering. ECCOMAS 2000; 2000

The aim of this work is to present the simulation of the mechanical behavior of brittle matrix and short fiber composite materials, emphasizing fiber reinforced concrete. The study describes the implementation in an explicit finite element dynamic analysis code [13] of an yield function that takes into account the mechanical properties of short fibers normally used in high performance concrete. The yield function implemented in the phasecorresponding to concrete is capable to calculate both the compression strength consideringplain concrete, as well as the tensile strength of this concrete matrix considering the tensilestrength of the short fibers.The numerical tests are made using Polypropylene and steel hooked ends fibers. Theircharacterization from the point of view of mechanical properties is done with conventionalmechanical experiments. The fibers are considered only in tension and a von Mises yieldfunction is used. Their interaction with the concrete matrix is obtained from the pull-out testresult, which is affected by the fiber shape, cross sectional dimensions and length. The pullout strength for an isolated fiber obtained in this test is related to the augmented tractionstrength of the specific concrete matrix. The composite mechanical properties are calculatedusing the mixing theory, considering experimental data and practical recommendationsregarding their participation in volume.In the numerical implementation, the non associated plastic flow for the yield function iscalculated for the stress state at each point of the continuum media using radial returnalgorithm. Stresses are affected by degradation of the tensioned concrete matrix, which isconsidered by an elasto-plastic damage function. The program is applied in the solution of abeam in three points flexure, the model representing a standard specimen for bending tests in concrete. Some examples are described and the obtained results are compared withexperimental data from the literature, showing that the proposed model is capable ofproducing good results in the stress analysis of fiber reinforced concrete.