Compressive Strength of Unreinforced Struts

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Title: Compressive Strength of Unreinforced Struts

Author(s): Lucas Laughery and Santiago Pujol

Publication: Structural Journal

Volume: 112

Issue: 05

Appears on pages(s): 617-624

Keywords: bottle struts; plain concrete; prismatic struts

Date: 9/1/2015

Abstract:
At present, the majority of published literature claims that the compressive unit strength of a plain concrete strut loaded over its full cross section is greater than the unit strength of the same strut loaded over a reduced width. The strength reduction in the latter case is attributed to the development of internal tension resulting from lateral spreading of internal stress. This tension is thought to cause lateral splitting failure before the strut reaches its full compressive strength. The current investigation tests the hypothesis that unreinforced struts have lower compressive unit strength when loaded in uniaxial compression over a reduced width. This is done through the testing of 32 unreinforced concrete specimens and the creation and analysis of a database containing all available results to date of tests on plain concrete struts loaded in uniaxial compression. The additional testing reported herein was intended to make up for a paucity of data from large planar bottle struts (height = 12 in. [305 mm]) tested alongside control prismatic struts. Of the 32 new specimens tested, 14 were loaded uniformly across their full cross section and 18 were loaded over a reduced width. In contrast to engineering consensus, analysis of the database including these new results suggests that the unit compressive strength of a planar concrete strut is independent of the ratio of its cross-sectional width to the width over which it is loaded.