Numerical and analytical modelling of masonry walls failure under waterborne debris impacts

Masonry walls are highly vulnerable to waterborne debris impact loads occurring during extreme hydrodynamic events. These loads are usually represented with a force–time (F-t) diagram calculated using analytical models. Such models are currently derived from elastic structures, neglecting the effects of potential failure mechanisms activated by the impact. At the same time, current design standards lack design prescriptions that consider structural failure in debris impact design. To address this gap, the present paper investigates the effects of structural failure on F-t diagrams and proposes a new model, the Energy and Impulse-Momentum Model (EIMM), to compute analytical nonlinear F-t diagrams that account for such structural nonlinearities. The focus is on masonry structures due to their popularity in the built environment, but the findings can be extended to any impact scenario. It is shown that structural failure significantly reduces the impact force due to the decrease in structural stiffness. A Performance Index, PI, is used to quantify this reduction and is proposed as a potential design parameter. It is also shown that the proposed EIMM can effectively compute nonlinear analytical F-t diagrams. The results of this research deliver new knowledge and methods for debris impact design of nonlinear structures needed to guarantee public technical safety of structures in extreme hydrodynamic events.