Manufacturing imperfection assessment of multi-leaf masonry panels

Structural stability is a major consideration in the design of structures. The stability is affected both by structure dimensions and by geometrical and mechanical imperfections. The intrinsic heterogeneity of historical masonry affects its structural behaviour; the identification of the local homogeneity degradation allows to define a new design approach to take on the structural rehabilitation of multi-leaf masonry structures. In this paper, the imperfection effects on the performances of multi-leaf masonry walls, considered as orthotropic material, are investigated using experimental and numerical approaches based on modal analysis [1, 2]. Unavoidable imperfections of workmanship, emphasized by mechanical orthotropy, affect the application of conventional design approach. After a first identification of the dynamic parameters - such as frequencies and modal shapes, of different multi-leaf masonry panels characterized by undamaged, damaged and strengthened fill - the model updating procedure has been applied to assess the local and global modal shapes. A Finite Element Model has been built simulating the fill by mono-dimensional element with different unidirectional stiffness between the external layers to distinguish and calibrate the local modal shapes and, then, the global response [3, 4]. The experimental and numerical data have been compared to analyse the reliability of the applied method [5]; the calibrated models have been tested through the non-linear static analysis and the results have been compared with the structural performances of the multi-leaf masonry panels subjected to the compressive loads.