Time-Scales for Redistribution of Stress in Creep of Structures

On the basis of some reasonable assumptions about the behaviour of structures in creep, a simple formula is derived for the time taken for the redistribution of stress in a structure, subject to step loading, from an initial state to a final steady state to be practically complete. The time taken is expressed in terms of the time taken for creep strain to become equal to a certain multiple of the elastic strain in a constant-stress creep test; this test is performed at a stress level which depends on the steady-state distribution of stress in the structure. The formula agrees remarkably well with numerical results in the literature, both for structures which are initially stress free and for structures with initial thermal stress. The formula seems to be well suited for practical use in engineering design.