Comparative study on reliability of ductility and strength limit states in design of reinforced concrete beams according to fib Model Code

Ductility is an important limit state for the design of reinforced concrete beams. For reinforced concrete beams designed based on the fib Model Code 2010, reliability of this limit state is investigated using reliability-based assessment with ductility defined by strain ratio and it is then compared with that of traditional strength limit states. The modelling uncertainty for the ductility limit state typically is much greater than that for structural strength limit state. Results show that the ductility ratio generally follows a right-skewed distribution, and due to variability in the material properties and model error, there is high variability in the ductility. This is reflected in the corresponding reliability indices of limit state defined for ductility. Some of the resulted reliability indices could be considered unacceptably low