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.
8D.D.3.2 Tension Members
Slenderness ratio KL/r of a member carrying axial tension only, shall not exceed 400.