Title:
A Two Parameter Stress Block for High-Strength Concrete
Author(s):
Mario M. Attard and Mark G. Stewart
Publication:
Structural Journal
Volume:
95
Issue:
3
Appears on pages(s):
305-317
Keywords:
beams (supports); columns (supports)high-strength concrete; probability theory; stress-strain relationships; structural design; structural reliability
DOI:
10.14359/548
Date:
5/1/1998
Abstract:
The rectangular stress block parameters in the current ACI Code are limited to concrete strengths in the range 20 to 50 MPa (2900 to 7250 psi). This paper looks at the applicability of the ACI rectangular stress block parameters to high-strength concretes. New rectangular stress block parameters are proposed that are based on a probabilistic analysis using a stress-strain relationship for high-strength concrete and that include estimates of variability and distribution of the input properties. A sensitivity analysis is also carried out to ascertain the effect of parameter uncertainty. The probabilistic models proposed can be used in a code calibration of design formula for high-strength concrete. It is shown that for a ductile singly-reinforced rectangular section, the ultimate moment capacity is relatively insensitive to the stress block model. Estimates of the ductility level at both ultimate and column capacity in primary compression failure, however, are significantly affected by the choice of the stress block model.