Integration of durability with structural design: An optimal life cycle cost based design procedure for reinforced concrete structures

The durability design of concrete structures is traditionally based on implicit and prescriptive requirements for materials, material constituents and structural dimensions. With the use of such rules, it is however not possible to visualize an explicit relationship for durability over the lifetime of a structure and determine what constitutes acceptable durability at an optimum cost.An explicit durability design procedure for the design of reinforced concrete structural elements is presented in this paper. The procedure attempts to directly integrate considerations of durability into the structural design process while ensuring lifetime cost optimization. The evaluation of durability is made on the basis of service life which is determined based on the principle of exceedance of defined limit states – a concept commonly used in structural design. Two limit states for corrosion of reinforcement induced by chloride ingress from sea water are used. The service life decides the magnitude and timing of future costs incurred during the design life of the structure. Tradeoffs between initial costs and future costs are examined to determine the optimum design alternative from a life cycle cost perspective. Further the influence of various design and environment variables on the life cycle cost and hence durability of the structure is also evaluated.