Title:
Size Effect in Punching Shear Failure of Slabs
Author(s):
Zdenek P. Bazant and Zhiping Cao
Publication:
Structural Journal
Volume:
84
Issue:
1
Appears on pages(s):
44-53
Keywords:
concrete slabs; cracking (fracturing); ductility; failure; punching shear; reviews; strains; structural design; tests; Structural Research
DOI:
10.14359/2785
Date:
1/1/1987
Abstract:
Punching shear tests of geometrically similar reinforced concrete slabs of different sizes are carried out. The nominal shear stress at failure is not constant, as assumed in the current design formulas, but decreases as the slab size increases. The observed size effect in punching shear strength is approximately described by an improved design formula which uses the size-effect law for brittle failures due to distributed cracking. Applicability of this law is further supported by measurements of deflection diagrams, which reveal that the post-peak load decline becomes steeper as the slab size increases. Previous test data by various investigators are also analyzed collectively as one large set. Due to the enormity of scatter within this set, the absence of geometrical similarity and the lack of significantly different slab sizes within any single test series, these previous test data neither corroborate nor contradict the applicability of the size-effect law to punching shear.