Abstract

LEAL GRACIANO, J. Martin et al. New expressions adopted by mexican code (NTCM, 2017) to calculate the shear strength of infill masonry walls. Ing. sísm [online]. 2019, n.100, pp.1-29. ISSN 0185-092X.

The new shear strength design expressions for infill-walls included in the 2017 release of the Mexican code are presented. Three failure modes are considered, crushing, sliding and diagonal tension. The expressions were adapted from those specified in the Canadian masonry code, to include the Mexican code strength parameters and to make the expressions refer, for the three failure modes, to a shear resistance. It was verified that the shear strength given by the new expressions is satisfactory after comparing their prediction to the results of an experimental campaign that is also presented herein.

The experimental investigation included six specimens, scaled 1:2, in which the study variables were the wall to frame stiffness ratio, the use of confining elements and horizontal reinforcement. The results indicate that the wall to frame stiffness ratio has an important effect on the cracking strength of the walls and the maximum shear strength of the system. Moreover, the contribution of horizontal reinforcement to the lateral strength depends on the wall to frame stiffness ratio, a phenomenon that the design expressions do not take into consideration. The confining elements surrounding the infill walls do not increase the lateral strength nor the displacement capacity of the system; however, they enhance the out of plane stability of the wall and the contact conditions between the wall and frame.

Keywords : masonry; infill wall; confinement; reinforcement; strength.

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