Creep analysis of compact cross-sections casted in consecutive stages – Part 1: General method

This paper introduces a general approach to the evaluation of the stress and strain time evolution under long term loading of concrete compact cross-sections casted and/or prestressed in consecutive stages.The overall cross-section can be made of reinforced concrete, prestressed concrete, structural steel or fiber reinforced polymer parts added at distinct stages of the construction work or during the life of the structural element. Moreover, the cross-section can be prestressed several times both during construction and after gaining the final shape. Therefore, the method herein suggested applies both to new structures casted in consecutive stages and to some problems related to rehabilitation or strengthening of concrete structures.The physics of this problem leads to a system of Volterra integral equations that, because of the complexity of the creep function usually adopted for concrete, has to be solved by means of a refined step-by-step time integration method which assures high precision to the output.This general approach and the computer program made with it will be used in a next paper to verify the degree of conformity of the solutions that can be obtained by means of much simpler approaches named algebrized methods.

► Evaluation of the time evolution of concrete sections made in consecutive stages.
► The method applies both to new structures and to problems related to retrofitting.
► The exact resolvent system is solved by means of a refined time integration method.