Rectangular Stress Block for High-Strength Concrete

© Copyright 2004, American Concrete InstituteThe use of high-strength concrete (HSC), with strengths reaching 130 MPa, has increased in recent years due to its superior performance and strength. Structures are designed and built using HSC, especially in columns of multistory buildings. The rectangular stress block specified in the ACI 318-02 Building Code for design of reinforced concrete elements was developed, however, on the basis of normal-strength concrete column tests. The applicability of the ACI rectangular stress block to higher-strength concretes becomes questionable, especially for members under high levels of axial compression. A new rectangular stress block is introduced in this paper for a wide range of concrete strengths between 20 and 130 MPa. The proposed stress block is verified against available test data. Column strengths computed using the stress block show good agreement with those recorded experimentally.Togay Ozbakkaloglu and Murat Saatciogl