Stress-strain curve for the design of high-strength concrete elements

Although the great advances in concrete technology have led to the possibility of obtaining ready-mix concrete with compressive strength around 100 MPa, some national and international codes for concrete structures do not cover concrete strengths above 50 MPa. Many codes are under revision, but some of them (including the Brazilian Code) will still not Include high strength concretes. Due to the different characteristics of higher strength concrete some design procedures traditionally used in normal strength concrete structures have to be changed. Different types of stress-strain relationships for concrete have been proposed for the non-linear analysis of member behavior and for the ultimate state analysis of high strength concrete elements under combined flexure and axial load. In this work comparisons are made between proposed stress-strain curves and between the axial load-moment interaction diagrams based on these curves. Comparisons of test results with these diagrams, for columns subjected to eccentric compression, give an idea of the different degrees of safety obtained using those curves.