Keywords: unreinforced masonry, finite element method, nonlinear analysis, domain partitioning approach, mesoscale model.

HREF="#macorini:3">3], where the actual geometry of brick masonry is considered by modelling brick and mortar separately, allows a realistic representation of the URM behaviour under extreme loading conditions. In general, the mesoscale approach enables most of the failure mechanisms to be captured, but it is inefficient for large-scale structural computations because of the excessive computational effort required. This renders the use of mesoscale monolithic models for the global analysis of entire buildings impractical.

To overcome this drawback, the computational strategy presented in the paper employs the domain partitioning approach, which is coupled with an advanced mesoscale finite element model for brick masonry. This model accounts for both material and geometric nonlinearity and relies on an accurate two-dimensional nonlinear interface element [3] for representing cracks and damage in the brick masonry. The employed mesoscale model enables the modelling of any three-dimensional arrangement for brick masonry, accounting for the in-plane stacking mode and the through-thickness geometry, and importantly it allows the investigation of both the in-plane and the out-of-plane response of unreinforced masonry panels. According to the domain partitioning approach, a parent masonry structure is divided into super-elements which are separately modelled as partitions. Each super-element corresponds to one partition and the number of element nodes connected to the parent structure is equal to the number of nodes at the partitioned boundary in the partition that it represents. Dual super-elements are used for modelling the child partitions as separate processes, where two-way communication between each pair of dual parent-child super-elements allows effective parallelisation of the nonlinear structural analysis simulation, thus achieving significant speed-up in the nonlinear analysis of large masonry structures.

The effectiveness of the proposed computational strategy is demonstrated through several numerical examples. The speed-up guaranteed by using an increased number of super-elements for representing the behaviour of a large URM panel is determined and discussed. Numerical comparisons are then provided considering the nonlinear response of a URM wall, where the ability of the detailed modelling approach for capturing the brittle nature of URM panel failure under shear forces is highlighted. Finally, the potential of the developed numerical strategy is confirmed in a nonlinear simulation investigating the response of a full-scale URM façade under in-plane loading.

1

P.B. Lourenço, J.G. Rots, "Multisurface Interface Model for Analysis of Masonry Structures", Journal of Engineering Mechanics (ASCE), 123(7), 660-668, 1997. doi:10.1061/(ASCE)0733-9399(1997)123:7(660)

2

L. Gambarotta, S. Lagomarsino, "Damage models for the seismic response of brick masonry shear walls. Part I: the mortar joint model and its applications", Earthquake Eng. Struct. Dynam., 26, 423-439, 1997. doi:10.1002/(SICI)1096-9845(199704)26:4<423::AID-EQE650>3.0.CO;2-#

3

L. Macorini, B.A. Izzuddin, "A non-linear interface element for 3D mesoscale analysis of brick-masonry structures", Int. J. Numer. Meth. Engng., 2010. doi:10.1002/nme.3046

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