Chapter 6 - Buckling Concepts
© 2006, 2008, 2011 T. Bartlett Quimby
Last Revised: 07/30/2011
As presented in Chapter 1, the homework problems involve the design of elements of three different structures plus some unrelated details. Please see the relevant links below for each structure. Consider developing a generic spreadsheet that you can apply to similar problems.
Problem M6.1: A W14x90 is used as a concentrically loaded column. In the plane of the web (i.e. the strong direction), the base of the column is pinned at the foundation and at the top is free to translate but not rotate. In the plane of the flanges (i.e. the weak direction), the base of the column is fixed and at the top is braced but free to rotate. The column is 25 ft long and is braced at mid height in the weak direction. Sketch both principle views of the column, complete with support conditions and the general buckled shape. Compute the slenderness (KL/r) of the column.
Problem M6.2: For the frame shown in MISCDET_STL 1/S5.2, determine the controlling effective lengths in each principle direction ((KL)x and (KL)y, in feet) for the indicated column segments and enter the results into a table similar to the table below:
Problem M6.3: Create a spreadsheet to determine the local buckling classification (i.e. compact, non-compact, or slender) for the types of sections indicated below. The spreadsheet is to allow the user to enter any value for Fy.
As none of the members have sizes in the moment frames, it is not possible to compute the effective lengths of the members in places other than where there are pinned connections.
All the connections in this structure are considered to be pinned and all frames braced, making the effective length coefficient the same for all members.
There are several compression only members in this truss. The most notable is the top chord of the truss. In the plane of the truss, the members are braced against lateral movement at the joints. Out of plane the top chord is restrained laterally only at the ends of the bridge.