Fracture Mechanics Models for Brittle Failure of Bottom Rails due to Uplift in Timber Frame Shear Walls

Figure 3

Crack development for bottom rail with pith oriented upwards (PU). (a) Mode 1 crack developing in a straight line, starting and propagating vertically at the centre of the bottom rail; (b) mode 1 crack developing in an oblique line initiating at the bottom surface of the bottom rail at a vertical position close to the edge of the washer and propagating towards the pith; (c) mode 1 crack developing in a straight line for a certain length and then following the annual rings; (d) mode 1 crack developing in an unusual direction, probably due to a weaker crack plane; (e) mode 1 crack developing towards the pith (pith in an unusual position); (f) mode 2 crack starting horizontally and then propagating vertically; and (g) mode 2 crack horizontally and then propagating vertically following the annual rings.

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