Hello.

I am running a nonlinear time history analysis on a wind turbine using abaqus. I give the ground motion as displacement amplitude in the boundary condition section. The problem is that while I obtain the acceleration of some nodes, say to acceleration, the beginning of the time history gives me a huge acceleration. It seems like the program understands it as an impulse. The rest of the output is in consistent with the modal analysis. whereas, when I use the acceleration ground input, I do not face the same problem, however, the free vibration part is not acceptable.

Any idea where I might have made a mistake?