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Dear Team STKO,

What is the meaning of the following error:
"FATAL:second_order_eqn: Complex roots.
when moving active surface.
B2=8.34901e-23 4AC=9.37715e-23"?

NB: I am conducting a ground response analysis under seismic loading.

Hi,
This error means that OpenSees is not able to solve the second-order equation somewhere in the model, that B^2 - 4*A*C is negative. There are could be different reasons that could lead to this numerical problem, for example, improper input parameters. Make sure that the parameters that you are using are correct for the PDMY(PIMY)material.

Best wishes,
Valentina