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Abstract: The crack band approach has been used in many engineering computations as a simple technique eliminating or reducing the sensitivity of numerical results to the size of finite elements in simulations that involve strain localization due to softening. In the present paper, this traditional technique is carefully analyzed and potential sources of errors are identified. The role of various components of the modeling strategy is elucidated by simple examples dealing with a one-dimensional tensile test and a two-dimensional model of a notched beam subjected to bending. The influence of the specific choice of finite elements, integration scheme and formula for estimation of the crack band width is analyzed. Particular attention is devoted to the differences among band width estimation methods based on element area or volume, on element projection, and on the idea proposed by Oliver . The results are summarized in the form of recommendations which can contribute to reduction of errors in practical simulations. [Copyright &y& Elsevier]

Abstract: This paper deals with simulating the mechanical response of fiber-reinforced cementitious composites (FRCCs) by means of a zero-thickness interface model formulated within the framework of discrete-crack approaches. Following a similar model already available in literature for plain concrete, the formulation of the interface element is further developed and extended to capture the key mechanical phenomena controlling the FRCC behavior. An original approach is introduced for reproducing the complex influence of fibers on the cracking phenomena of the concrete/mortar matrix. Numerical analyses demonstrate the capabilities of the proposed model and show a very good agreement with experimental results on FRCC tests. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to gain insight into finite element discretizations of shells using the basic shell mathematical model and, in particular, regarding the sources of “locking”. We briefly review the “basic shell mathematical model” and present a formulation of shell finite elements based on this model. These shell finite elements are equivalent to the widely-used continuum mechanics based shell finite elements. We consider a free hyperboloid shell problem, which is known to be difficult to solve accurately. Using a fine mesh of MITC9 elements based on the basic shell mathematical model, a detailed analysis is performed giving the distributions of all strain terms. A similar analysis using the MITC6 shell element shows why this element locks when the shell thickness is very small. [Copyright &y& Elsevier]