Title:
Stress Block Parameters for High-Strength
Concrete Members
Author(s):
Sungjin Bae and Oguzhan Bayrak
Publication:
Structural Journal
Volume:
100
Issue:
5
Appears on pages(s):
626-636
Keywords:
cover; high-strength concrete; spalling; strain; stress.
DOI:
10.14359/12804
Date:
9/1/2003
Abstract:
In high-strength concrete (HSC) column tests, early spalling of cover concrete has been reported by researchers. Although early cover spalling and associated strength loss in HSC columns have been observed by some researchers, a rational way to incorporate this phenomenon in the building code has not yet been introduced. Moreover, the use of ACI 318-02 stress block parameters to estimate the strength of HSC columns results in unconservative predictions for moment capacity in some cases. Hence, modification of ACI 318-02 stress block parameters to incorporate early cover spalling in HSC columns is of great significance. With this motivation, the experimental results obtained during the course of the ongoing research and those available in the literature were used to study the accuracy and conservativeness of the ACI 318-02 stress block parameters. Based on experimental evidence, it was decided to reduce the ultimate compressive strain limit of ACI 318-02 to 0.0025 for HSC members such that the capacity of these members can be evaluated prior to cover spalling. Bearing this in mind, a new set of stress block factors was analytically derived and validated with experimental data. Stress block parameters proposed herein provide similar levels of conservativeness and accuracy for normal-strength concrete and high-strength concrete.