Elastic Deflections of Concrete Slabs Reinforced with Different Types of Steel Fibers

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Title: Elastic Deflections of Concrete Slabs Reinforced with Different Types of Steel Fibers

Author(s): T. S. Lok and J. S. Pei

Publication: Special Publication

Volume: 161

Issue:

Appears on pages(s): 267-284

Keywords: cracking (fracturing); deflection; elastic properties; fibers; flexural strength; loads (forces); slabs; stiffness; Structural Research

Date: 4/1/1996

Abstract:
Load-deflection responses of simply-supported (SS) and simply-supported all-round (SSAR) steel fiber reinforced (SFR) concrete square slabs subjected to a central point load have been obtained. The slabs measured 810 mm x 810 mm x 50 mm. The elastic response alone is of particular interest and presented here because this has a major influence on the durability of SFR concrete. Results for each SFR concrete slab are compared with theoretical elastic solutions for both boundary conditions and also with the behavior of identical plain concrete and weldmesh reinforced slabs in each case. A modified depth instead of the full slab thickness is proposed for estimating the elastic response of SFR slabs for the two boundary conditions; the depth effectively reduces the elastic stiffness of the cross section. The limiting load level at which the initial response may be considered as linear is established, but the limiting load is dependent on the behavior of the slab. This limiting load level is compared with results calculated from a modified empirical expression for predicting the load at which first crack is perceived to occur. In the empirical expression, a triangular linear stress block with the modified depth is used. On average, the modified depth is about 0.7 times the overall SFR concrete slab thickness for both the SS and SSAR boundary cases. The influence of fiber type, fiber concentration, and boundary condition on the modified depth is not significant.