8D.D.3 Stability Requirements
Slenderness ratios are calculated for all members and checked against the appropriate maximum values. The following are the default values used in STAAD.Pro.
8D.D.3.1 Compression Member
| Type of Member | Slenderness Limit |
|---|---|
| Leg Members, ground wire peak member and lower members of cross arms in compression | 120 |
| Other members carrying computed stress | 200 |
| Redundant members and those carrying nominal stresses | 250 |
Slenderness ratios of compression members are determined as follows:
| ELA Value | Type of Member | Calculation of KL/r |
|---|---|---|
| 1 | Leg sections or joint members bolted at connections in both faces | L/r |
| 2 | Members with concentric loading at both ends of the unsupported panel with values of L/r up to and including 120 | L/r |
| 3 | Member with concentric loading at one end and normal eccentricities at the other end of the unsupported panel for value of L/r up to and including 120 | 30 + 0.75L/r |
| 4 | Members with normal framing eccentricities at both ends of the unsupported panel for values of L/r up to and including 120 | 60 + 0.5L/r |
| 5 | Member unrestrained against rotation at both ends of the unsupported panel for value of L/r from 120 to 200 | L/r |
| 6 | Members partially restrained against rotation at one end of the unsupported panel for values of L/r over 120 and up to and including 225 | 28.6 + 0.762L/r |
| 7 | Members partially restrained against rotation at both ends of the unsupported panel for values of L/r over 120 and up to and including 250 | 46.2 + 0.615L/r |
If the value for ELA specified for any particular member results in the L/r ratio to fall outside of the specified range, then STAAD.Pro ignores this input and evaluates the slenderness ratio using the KL/r formula.