JKAU: Eng. Sci., Vol. 2, pp. l83-l94 (1410 A.H. 11990 A.D.) Stress-Strain Relationship for Concrete in Compression Madel of Local Materials ANIS MOHAMAD ALI, BJ. FARID AND A.I.M. AL-JANABI Civil Engineering Department, College of Engineering, University of Basrah, Iraq. ABSTRACT An attempt is made to evaluate the stress-strain relationship for concrete under uniaxial compression made of local materials. Experimental program was carried out on concrete specimens to evaluate various parameters involved. The proposed equations fit the experimental results with excellent agree- ment, hence, the distribution of stress, in concrete can be represented ac- cordingly. Introduction For any sectional analysis, the evaluation and definition of the stress-strain relation- ship of concrete are required. Though a number of expressions are available, yet it may not be possible to define the relationship using one approach and completely represent the actual concrete behaviour in both the ascending and descending por- tion under the test conditions. It is known to most investigators that this is due to the fact that stress-strain re- lationship is greatly influenced by a number of factors. The shape of stress-strain curve is affected by the duration of loading and straining which is associated with the mechanism of internal progressive microcracking 111 . The theory of microcracking has led to only a better understanding of the be- haviour of structural concrete section. Investigators working on the ultimate moment capacity of R.C. section are quiet familiar with the available numerical approximation and empirical formulae to evaJuate stress block parameters in which stress strain relationship comes first. 183