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

Figure 4

Crack development for bottom rail with pith oriented downwards (PD). (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 starting at a location close to the pith and propagating towards the loaded edge of the bottom rail; (c) mode 1 crack first following the annual rings and then propagating in a straight line towards the line of the anchor bolts; (d) mode 1 crack initiating off the centre on the bottom surface of the bottom rail and following an annual ring for a certain length and then jumping to another annual ring and propagating towards the centre of the upper surface of the bottom rail; (e) mode 1 crack propagating in an unusual “zig-zag” line across the annual rings; (f) mode 2 crack development, starting horizontally and then propagating vertically following the annual rings.

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(b)

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(f)