Brittle punching failure can occur due to the transfer of
shear forces combined with unbalanced moments between
slabs and columns. During an earthquake, significant
horizontal displacement of a flat plate-column connection
may occur, resulting in unbalanced moments that induce
additional slab shear stresses. As a result, some flat plate
structures have collapsed by punching shear in past earthquakes
(Berg and Stratta 1964; Yanev et al. 1991; Mitchell
et al. 1990, 1995). During the 1985 Mexico earthquake
(Yanev et al. 1991), 91 waffle-slab and solid-slab buildings
collapsed, and another 44 buildings suffered severe damage.
Hueste and Wight (1999) studied a building with a posttensioned
flat plate that experienced punching shear failures
during the 1994 Northridge, CA, earthquake. Their study
provided a relationship between the level of gravity load and
the maximum story drift ratio that a flat plate-column
connection can undergo without punching shear failure. The
displacement-induced unbalanced moments and resulting
shear forces at flat plate-column connections, although
unintended, should be designed to prevent brittle punching
shear failure. Even when an independent lateral-forceresisting
system is provided, flat plate-column connections
should be designed to accommodate the moments and shear
forces associated with the displacements during earthquakes.
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| Number of Pages : | 34 |
| Published : | 04/01/2010 |
