For BS5950:2000, selecting the Assign-Sway-Sensitive Method… command causes the Sway-Sensitive Design Method dialog box to be displayed. From this dialog the engineer can specify the design approach to be applied to the member for a specific axis. That is, per BS5950-2.4.2.7 the user can designate to use the Effective Length approach per 2.4.2.7a. or the Amplified Sway Approach per 2.4.2.7b. For the amplified sway approaches the user can designate to have the program calculate kAmp for each load combination or to use a specified value.

For the Amplified Sway Approach if the Calculate (Per Load Combination) option is selected then the program will calculate the lateral story drift at the position of each member being designed (for all floors), for only the factored notional loads in the load combination. For that specific combination the drifts are then used to calculate λcr per 2.4.2.6 and in turn are used to calculate kAmp per 2.4.2.7b.1. Note that the user will need to create and analyze notional load cases to make use of this option. Refer to the technical section for more information on calculating λcr for load combinations.

The sway-sensitive design method criteria are only used by the BS5950:2000 steel design codes and ONLY if p-delta analysis was not performed.

Select the axis checkbox to make an assignment to a specific member axis. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple members (click on Fence) or to all members (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel members.

To view what sway sensitive design method is assigned to each member select the appropriate option from the View-Members Dialog.