Flexural capacity predictions of self-compacting concrete beams using stress-strain relationship in axial compression

Due to its unique composition, self-compacting concrete (SCC) may have stress-strain characteristics that are significantly different from those of conventionally vibrated concrete (CVC). An experimental investigation was carried out to generate complete stress-strain curves for SCC in axial compression by testing 162 standard cylindrical specimens of strength 35-70 MPa. The accuracy of analytical models for CVC selected from the literature in predicting the stress-strain behaviour of the SCC mixtures is discussed and their inadequacies are highlighted. A new constitutive model covering a wide range of concrete strengths is proposed for SCC. The equivalent rectangular stress block specified in current design codes for flexural capacity predictions was developed on the basis of tests on CVC; given the observed differences in the stress-strain behaviour of CVC and SCC, its applicability to structural design of SCC members becomes questionable. On the basis of the proposed constitutive model for SCC, a new equivalent rectangular stress block valid for concrete strengths of up to 70 MPa is presented for analysis of flexural capacity. The flexural capacity predictions of the proposed stress block are compared with experimental data from the present work and other investigations reported in the literature, and good agreement was obtained. A simple analytical approach is presented for predictive assessment of the load-deflection behaviour of SCC beams with a reasonable degree of accuracy.