Stuart, P.E., S.E., P.Eng.
course will provide the user with a basic understanding of the "Leaner
Column" concept as it relates to the general stability provided to a structure
in relationship to each individual compression element or column. This course
will provide the user with methods and recommendations for incorporating "Leaner
Columns" into the design of both rigid and braced frames.
This course includes a multiple choice quiz at the end.
The general stability of a structure as a whole must be provided as it relates to the each individual column not functioning as a part of the overall lateral bracing system. Consideration must therefore be given to the load effects resulting from the deflected shape of the structure. The stability of a column not involved with the lateral bracing system is therefore dependent on the rigidity of the columns associated with the lateral bracing system or rigid bents. The columns that are dependent on the rigid frame columns are referred to as "Leaner Columns".
The simplest form of a leaning column is a pinned end column which has no lateral stability of itsí own therefore, it relies on other parts of the structure to provide for itsí lateral stability. The impact of leaning columns on the lateral stability of frames to which they are attached must be accounted for in design. Leaner columns results from the type of structural framing and occur with both ASD and LRFD. Leaner columns are gravity load only columns and apply to both rigid and some braced frames.
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A. The difference between the Yura and Lim and McNamara approaches has to do with the use of an effective load versus an effective length. With the effective load approach, the column is designed with a shorter effective length but a larger load given by (P+Q). With the effective length approach, the load is maintained, however; the effective length is made larger through manipulation of the K value.
B. The Yura method can give overly conservative results but can be modified to yield solutions similar to the Lim and McNamara approach.
C. The LeMessurier is recognized as the most accurate method.
D. It is recommended that different stages of design can benefit from the different levels of accuracy provided by the above methods. Initial or preliminary design could use the Yura method while the LeMessurier method would be more appropriate for final design.
E. Software such
as RamSteel does not automatically account for leaner columns. It is possible
however to modify the effective length factors for the lateral frame analysis
columns to account the effects of leaner columns elsewhere in the structure.
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.