Computational Strategies for Frames with Infill Walls: Discrete and Smeared Crack Analyses and Seismic Fragility
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Several computational strategies for masonry structures, and particularly for frames with masonry infills, are presented. Three levels of details for the computational models are explored. Micro-modeling of masonry is presented first where the mortar joints are mod-eled using interface elements. Subsequently, a different approach is provided where various techniques for masonry composite are discussed. These models may be considered of an intermediate level of detail (meso-modeling) where damage mechanisms are accounted for in the form of smeared cracking using homogeneous properties for masonry. Numerical simulations involving smeared cracking face several problems due to mesh-sensitivity. To circumvent these problems, the standard smeared cracking is reformulated to allow for a systematic adaptation of the crack band width. This idea led to the development of the evolutionary characteristic length method, along with an adaptive strategy for the finite element discretization with mesh enrichment. This technique can handle nonlinearities produced by both smeared cracking and interface conditions. The third level of modeling (macro-modeling) is special for masonry infill walls where equivalent nonlinear truss ele-ments are used to replace the effect of the walls on the bounding frames. This modeling technique is useful as a design approach for masonry infills. Finally, further simplification of modeling frames with and without masonry infills is considered by using equivalent single degree of freedom systems based on the dynamic plastic hinge method. This approximate computational approach is utilized for the seismic fragility evaluation.