doi:10.1016/S0020-7683(03)00289-0 
Copyright © 2003 Elsevier Ltd. All rights reserved.
Lightning-induced fracture of masonry and rock
James F. Wilson
, 
Duke University, 6319 Mimosa, Dr. Chapel Hill, NC 27514, USA
Received 15 November 2002;
revised 20 April 2003.
Available online 25 June 2003.
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Abstract
As a lightning channel on its way to ground meets a standing masonry or rock structure, radiant energy from the channel can induce a thermal shock of sufficient intensity to cause the structure to fracture and collapse. Mathematical models for two such structural failure mechanisms are proposed: one describing violent surface separations or spalling, and the other characterizing internal cracking from sudden increased pore pressure in the solid. Experimental data and case studies are used to complement these theories of lightning-induced failure.
Author Keywords: Concrete; Elasticity; Fracture; Lightning; Masonry; Stone; Thermal shock
Fig. 1. The strip model for spalling showing: (a) a vertical section of the lightning channel core, which is tangent to the surface of half-space and (b) the cross-section for the plane z=0.
Fig. 2. Cross-sections of the spalling model showing: (a) thermal flux and edge load on the isolated, two-dimensional hydrostatic strip and (b) thermal loading of half-space.
Fig. 3. Normal stresses as a function of depth for the spalling model, on the plane of symmetry
x=0. The shear stress is zero on this plane.
Fig. 4. Internal crack model showing (a) orientation of the penny-shaped, water-filled cavity, (b) cavity subjected to a far-field uniform stress and (c) the cavity subjected to opposing central wall loads.
Fig. 5. Pressure–temperature behavior for a fixed mass of water: (a) water confined in a rigid cavity (fixed volume) and (b) water confined to a cavity in a concrete block that expands freely with increasing temperature, where α
0=10.3×10
−6 °C
−1.
Fig. 6. Representations of consecutive video frames for the Case A experiment in which a laboratory spark strikes an ungrounded gravel concrete building block: (a) the channel spark and block just prior to fracture and (b) the fractured block at a time 0.033 s later, showing some spalling at the base and the dispersing plasma.
Fig. 7. Case A: a simulation of the experiment. Snapshot views show the predicted temperature distributions with depth on the plane
x=0, for several times up to the total flash time of Δ
t=0.1 s. The heat flux is
F0=142 kW/m
2.
Fig. 8. Cases A and B: predicted temperature distributions with depth on the plane
x=0, based on a nominal lightning leader with a heat flux of
F0=60.6 kW/m
2 and a total flash time of Δ
t=0.5 s.
Fig. 9. This is a photograph of a sandstone monument that toppled when it was struck by lightning in 1980. Spalling is observed at its base, at the right of the photograph; and the deep midwidth fracture extends the full 4 m length of this stone. A partial view of one of the remaining 27 upright stones in this historic Ring of Brodgar, located in the Orkney Islands, UK, is observed in the upper left corner of the photograph.
Table 1. Selected properties measured for streaked lightning stepped leaders ([Krider, 1982]; [Uman, 1984])
Table 2. Properties of materials for two case studies ([Cordon, 1979]; [Deere and Miller, 1966]; [McAdams, 1954])
Table 3. Computed results for the two case studies
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