The Precision of Toughness Indexes Based on Multiples of First-Crack Deflections

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Title: The Precision of Toughness Indexes Based on Multiples of First-Crack Deflections

Author(s): B. Barr and E. B. Dawood Hasso

Publication: Journal Proceedings

Volume: 82

Issue: 6

Appears on pages(s): 870-876

Keywords: cracking (fracturing); deflection; fiber reinforced concretes;load-deflection curve; polypropylene fibers.

Date: 11/1/1985

Abstract:
Particular attention has been given in recently to the use of various multiples of first-crack deflections to define areas under load-deflection graphs to evaluate the toughness of fiber reinforced concrete materials. The present study investigates various multiples of first-crack deflection, the residual load at first crack, and prescribed deflections (as defined by ACI Committee 544’). To obtain the best precision for toughness index determination, the area under the load-deflection graph is considered out to twice the first graph deflection. The variation of toughness index values is shown to increase with an increase in the area of the post-cracking curve. Results of deflection-controlled, modulus of rupture, and notched-beam tests are presented.