I am modelling a FRP strengthening Rc beams under cyclic load. I am using sine load. When i decrease the time step size(0.1,0.01,0.001), the deflection increases every time. But with very small time step size, there is convergence problem. I have to run my model for 2 million cycles, so very very small time step size may not work for me. How can i decide the time step size? Any references for cyclic load would be highly appreciable.
Thanks
Hi. Instead of a transient problem, couldn't you use a harmonic analysis? In that case you can apply cyclic load and get the response of the structure in a full cycle. If you have properties of the beam that change through time than you can use a do-loop and simulate these cycles you want to implement.
Thanks for the answer.. In my case, frequency and amplitude of load are constant. yeah, i am using user subroutine for the properties which change with time. My load function is (1000*sin(6*pi*time)+50). Do you think harmonic analysis will work for this ? What do you think the best way to run this load for about 2 million cycle?
You Can apply the load using Functions.
Regarding choosing appropriate time step.It depends upon following factors.
Material model.
Nonlinear numerical implementation algorithm .(Newton raphson,Modified N R,Line search,Arc length,Dynamic stability)
Stability criteria in the transient analysis.
Input frequency of the applied load.
Model needs to be calibrated analyzing above parameters.
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