Simplification of Creep and Shrinkage Analysis of Segmental Bridges

The time-dependent concrete creep and shrinkage effects on segmental bridges are more critical than on other types of concrete bridges. Creep strains develop more when concrete is loaded in a younger age than in an older age, and it affects more on loss of prestressing and displacements because of prestressing. Creep and shrinkage analyses are considered an essential part for segmental bridge design and analysis, especially for the cast in situ segmental bridges or concrete bridges with an application of large quantities of prestressing. The introduction of a creep/shrinkage mathematic model into the formation of a stiffness matrix limits the evolution of a finite-element analysis (FEA) package and the adoption of a new model. Based on the fact that the creep development is nonlinear only in the time domain and linear to loadings, this paper introduces a novel time incremental method for creep and shrinkage analysis and its implementation to a FEA package. The equilibrium after a tiny time step will be reached to balance whatever creep and shrinkage strains have developed during that time. The incremental redistribution loads will cause further creep effects at an older loading age. In addition to external loads caused by construction phase changes at specific time ordinates, each incremental redistribution load will act as an external load at a corresponding time. With today's advanced computer technologies, the integration of these effects can be solved. The advantage of this simplified method is the separation of the creep/shrinkage model and FEA kernel. It is favorable to a modern modular bridge design and analysis system. A T-shape frame bridge constructed segmentally is included as a case study to illustrate the application of this method. (C) 2014 American Society of Civil Engineers.