Optimization for two Stifnesses in X and in Y for one component

Hallo Guys,

i have strated using Optistruct newly (4 Months). may Problem is as following.

i have a component which should not brake at 2 different load one in X direction and in Y direction. for x_direction i should reach a load of 20 KN without fracture, for Y-direction i should reach 15 kN without Fracture.

This optimization Problem Need to be solved once with Respekt to the 2 variables.

for one variable i can solve it, however for two variables i could not be able doing it.

any help is appreciated!!