To define the member parameters used in an AISC 360 direct analysis, use the following procedure.

1. On the Loading ribbon tab, select the Direct Analysis tool in the Define Load Systems group. The Create New Load Items dialog open.
2. Specify the initial τ_b value: Members whose flexural stiffness are considered to contribute to the lateral stiffness of the structure will have their flexural stiffness (EI) reduced by 0.8×τ_b .
   1. Select the FLEX Parameter tab.
   2. Type a FLEX value.
   3. Click Add.
3. (Optional) Identify any axial members which contribute to the lateral stiffness of the structure:
   1. Select the AXIAL Parameter tab.
   2. Click Add.
4. Click Close.
5. In the Load & Definition dialog, expand the Definitions > Direct Analysis Definition group.
6. Assign each of the FLEX and AXIAL parameters listed to the corresponding members in the model.