Nonlinear Creep Buckling of Reinforced Concrete Columns

This model accounts not only for the rapid increase of creep at high compressive stress (flow) but also for the decrease of creep observed for subsequent load increments after a long period of low sustained compressive stress (adaptation). A simply supported column is analyzed for typical load histories: sustained loading; short-time loading to failure; and sustained load followed by short-time loading to failure. Numerical results confirm that the flow nonlinearity makes the column fail in a finite time and the adaptation nonlinearity makes the response to the short-time load applied after a long period of a low sustained load stiffer. Also, there is a substantial difference in the column strength for the same load duration depending upon the loading history, especially the ratio of constant sustained load (dead load) and short-time load (live load) and their durations. This could be taken into account in setting the safety factors for columns subjected to dead and live loads of various ratios.