Definition of the near collapse in-plane drift capacity of rocking unreinforced masonry walls for the Dutch national guidelines

F. Messali, J.G. Rots

Delft University of Technology, the Netherlands

The in plane drift capacity of unreinforced masonry (URM) piers is an essential aspect in the seismic assessment of existing URM structures. Several empirical models are recommended in international codes, but none of them can accurately predict the drift at near collapse (NC) of URM piers that undergo rocking failure, also known as flexural failure. This work presents an update of an alternative empirical equation recently published by the authors. Starting from the original empirical equation, three correction factors are introduced (i) to account for the specific safety philosophy adopted by the Dutch guidelines NPR 9998, and also (ii) to consider the influence of alternative definitions of the NC drift capacity and (iii) of dynamic and short duration effects. The calibration process has been conducted by making use of a large dataset representative of Dutch clay and calcium silicate URM piers, and allowed for the identification of proper values of the correction factors. A final formulation of the empirical equation is presented. This formulation is currently recommended in NPR 9998.

Key words: Unreinforced masonry (URM), in-plane, drift capacity, calcium silicate masonry, clay brick masonry, empirical model