Hi Ramesh,
We presume you are asking about the Z displacement at joint 391.
In load case 3, you have a 3 kN force applied along global Z at joint 375.
That load produces torsion on member 599. That member is assigned a UC150X23.4 which is weak in torsion (IX for that section is only 5.02 cm^4).
If you replace it with a section that has a high torsional constant, like a European Square Hollow section 150X5SHS whose IX is 1550 cm^4, you will find that the Z displacement at joint 391 drops significantly.
We presume you are asking about the Z displacement at joint 391.
In load case 3, you have a 3 kN force applied along global Z at joint 375.
That load produces torsion on member 599. That member is assigned a UC150X23.4 which is weak in torsion (IX for that section is only 5.02 cm^4).
If you replace it with a section that has a high torsional constant, like a European Square Hollow section 150X5SHS whose IX is 1550 cm^4, you will find that the Z displacement at joint 391 drops significantly.