Methods of assessing concrete creep in prestressed bridge structures

The paper discusses the phenomenon of concrete creep, its mechanical models and simplified as well as more sophisticated methods of estimating creep effects applied in the design of bridge structures. The section on simplified methods describes the metod of substitutive concrete elasticity modulus and the method of estimating creep effects with the correction factor ��creep for spans with precast beams. Among the precise methods, it presents the modified effective modulus method (Trost 1967), age-adjusted effective modulus method (Bažant 1972) and the general incremental method according to the linear theory of elasticity. Methods for computationally accounting for creep according to current PN-EN standards, withdrawn Polish standards, and recommendations from foreign literature are characterized. The impact of creep on the redistribution of internal forces during the incremental erection of the structure was demonstrated using examples of a viaduct made of precast beams and a bridge constructed using balanced cantilever method. Attention was drawn to the possibilities of extending the description of creep phenomena in concrete bridge structures using the conceptual framework of fractional-order derivatives.