Page 480 - Forensic Structural Engineering Handbook

MASONRY STRUCTURES 13.25

Foundation settlement Wall opening

Deflection
FIGURE 13.17 Corner settlement or differential column movement.

Deflection

FIGURE 13.18 Shear failure.

Collapse. Absence of a horizontal expansion joint under a shelf angle supporting brick
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masonry on a concrete structure has led to collapse of several masonry walls. Masonry is
typically supported on shelf angles attached to the concrete frame. Concrete frames con-
tract owing to shrinkage, creep, and elastic deformation. Clay brick masonry expands
owing to temperature increase, freezing, and moisture absorption. If masonry is held vice
like between shelf angles, the differential movement induces an eccentric compressive
force on the masonry, which can buckle inadequately anchored masonry (see Fig. 13.24).
On May 16, 1968, in Ronan Point, England, a gas explosion occurred in a bathroom on
the eighteenth floor of a multistory apartment building. The explosion caused a progressive
collapse that drew public attention to the adequacy of buildings to resist accidental dam-
age. Since then, there has been extensive research and discussion about the robustness and
stability of buildings. Much of available published information relates to masonry struc-
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tures, which were thought to be susceptible to such damage. Lai and Leyendecker each
provide a review of the literature on the stability of masonry buildings against accidental
damage.