Masonry, though atraditional material which has been used for construction for ages, is a complex material. It is a complex composite material, and its mechanical behavior, which is influenced by a large number of factors, is not generally well understood. In engineering practice, many engineers have adopted an elastic analysis for the structural behavior of masonry using rather arbitrary elastic parameters and strengths of masonry. Such analyses can give wrong and misleading results. The proper way to obtain elastic parameters of masonry is through a procedure of homogenization described in the next section.
The effect of nonlinearity (i.e., tensile crack, compressive failure, and so on.) to the behavior of masonry model is very significant and must be accurately taken into account in analyzing the ultimate behavior of masonry structures. Having their own advantages and restrictions, many researches have been conducted, for instance,“Equivalent nonlinear stress-strain concept” of J. S. Lee & G. N. Pande1, Tomaževic’s “Story-Mechanism”2, the finite element analysis approach of
Calderini & Lagomarsino3, and “Equivalent frame idealization” by Magenes et al.4. Thus, in practical application of crack effect to the masonry structure, one must be well aware of unique characteristics of each of the nonlinear models for masonry structure. The main concept of the nonlinear masonry model adopted in the masonry model of MIDAS is based on the line of theory of J.S. Lee & G. N. Pande and described later.Nonlinear Masonry Material Model