Navigation:  Step-By-Step Examples > Example 17: Design of Steel Column

Problem Description

Select an ASTM A992 W-shape with a 10-in nominal depth to carry the following load effects:

Pu = 30 kips, Mux = 90 kip-ft, Muy = 12 kip-ft.  

The unbraced length is 14 ft and the ends are pinned.  Cb = 1.14.  The member is non-sway.

[Ref 23, Example H.4].  

 

Suggested Modeling Steps

▪Set proper units from Settings and Tools > Units & Precisions.  

 

 

▪Define the material from Modify > Member Properties > Materials using the standard steel Steel-A992--Fy50.  Steel properties such as Fy and Fu are set automatically.

 

 

▪Define the section W10x12 (or any W-shape) from Modify > Member Properties > Sections using the AISC table.  

 

 

▪Define the two nodes from Tables > Nodes.  

 

 

▪Define the one beam from Tables > Members

 

 

▪Define the one supports from Tables > Supports.  Please note the first node has X, Y Z, and OX DOFs fixed.  The second node has Y and Z DOFs fixed.  The fixity in OX direction at the first node is needed to ensure the stability of the 3D Frame.

 

 

▪Define the nodal loads from Tables > Nodal Loads.  Please note we enter the load effects as nodal loads as we do not have the exact load condition in the original example.  We need to enter Cb manually later instead of letting the program to calculate it for us automatically.

 

 

▪Define the load combination from Create > Load Combinations.  Make sure the “Perform Steel Design using this Load Combination” is checked.

 

 

▪Set structural model as 3D Frame from Analysis > Analysis Options.  Run Static Analysis to make static analysis results available for steel design.

 

 

▪Define the model design option from Steel Design > Steel Design Criteria > Steel Design Criteria.  Make sure the “Consider moment magnification factor B1” is checked.

 

 

▪Define the steel member design criteria from Steel Design > Steel Design Criteria > Steel Member Design Criteria.  Use “W10” as the section prefix as we want to find the lightest W10 section.  For this example, we manually enter Cb = 1.14 (The program would calculate Cb automatically if Cb is entered 0.0). Also, since we set Lb, Lux, Luy and Luz to be zero, the program will use the member actual length for each of them.

 

 

▪Define the steel member input from Steel Design > Steel Member Input.  

 

 

▪Perform the steel design from Steel Design > Perform Steel Design.  

 

▪View the steel design results from Steel Design > Steel Design Results.  By default, up to 10 candidate sections are available.  The original section W10x12 is not adequate with critical ratio = 9.64318 (> 1.0).  The first section that is adequate is W10x33 with critical ratio = 0.978576 (< 1.0).  At this point, you can update the member section to be W10x33, reanalyze the model and perform steel design again.

 

You can also view the detailed step-by-step calculation procedures for the most critical load condition on each member.