YEKRANGNIA, MOHAMMAD1; BAKHSHI, ALI2; GHANNAD, MOHAMMAD ALI3

1 PhD. Candidate, Sharif University of Technology, Department of Civil Engineering, yekrangnia@mehr.sharif.ir

2 Associate professor, Sharif University of Technology, Department of Civil Engineering, bakhshi@shar

Although there are several studies on the behaviour of Confined Masonry (CM) walls, few of them aimed at proposing a force-displacement model based on true nature of these structural systems. Most of these models have been originated from compressive strut models extensively used for infill walls. However, this hypothesis contradicts with the observed behaviour of such buildings i.e. diagonal cracks associated with shear failure at the ends of vertical ties which is considered a brittle failure mode. In other words, although confining elements increase masonry walls ductility, the final failure mode is brittle without any strength degradation. In this paper, a backbone model for CM walls, taking into account the observed failure modes in past earthquakes and experimental studies is proposed. Unlike some of the related previous studies, the model is based on analytical studies and its capability in predicting in-plane seismic performance of CM walls is calibrated against several experimental data. Comparison of the results with that of other models indicate that the proposed model can be reliably utilized in design and vulnerability assessment projects of CM structures. The results of the proposed model indicate that contribution of confining ties in strength capacity of masonry walls diminishes with the walls having considerable length; while their assistance in providing extra ductility is less affected by this parameter.

Keywords: Confined masonry buildings, Force-Displacement model, Shear failure