Curvature ductility of RC sections based on eurocode: Analytical procedure

Correct estimate of curvature ductility of reinforced concrete members has always been an attractive subject of study as it engenders a reliable estimate of capacity of buildings under seismic loads. The majority of the building stock needs structural assessment to certify their safety under revised seismic loads by new codes. Structural assessment of existing buildings, by employing nonlinear analyses tools like pushover, needs an accurate input of moment-curvature relationship for reliable results. In the present study, nonlinear characteristics of constitutive materials are mathematically modelled according to Eurocode, currently in prevalence and analytical predictions of curvature ductility of reinforced concrete sections are presented. Relationships, in explicit form, to estimate the moment-curvature response are proposed, leading to closed form solutions after their verification with those obtained from numerical procedures. The purpose is to estimate curvature ductility under service loads in a simpler closed form manner. The influence of longitudinal tensile and compression steel reinforcement ratios on curvature ductility is also examined and discussed. The spread sheet program used to estimate the moment-curvature relationship, after simplifying the complexities involved in such estimate, predicts in good agreement with the proposed analytical expressions. Avoiding somewhat tedious hand calculations and approximations required in conventional iterative design procedures, the proposed estimate of curvature ductility avoids errors and potentially unsafe design.