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Wood Column

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This module designs wood columns that are subject to axial loads and lateral bending loads about both axes.  Click here for a video:


The user can select ASD or LRFD design methods and has access to a large built-in database of wood sizes and NDS species stress grades. Values of KF and phi are automatically determined and applied for the LRFD method.


All calculations are according to the NDS code.


The screen capture below shows the full screen for wood column design. See items below for descriptions of items that are specific to the Wood Column module.


For general description of the module, end fixity, loads, and load combinations click here. For slenderness description click here.




General Tab

The Design Stresses area bubbled in the screen capture below is unique to the wood column selection. This area enables you to specify the base design values for the wood species and grade of interest.




You can either enter these values manually, or you can click the clipP603button to display the Wood Stress Database.


Column Data Tab

All of the information on this tab is unique to a wood column.


The area bubbled in red is where you specify the column cross section. Use the clipP604button to display the built-in database of wood sections (solid-sawn, glulam, and manufactured sections are available). You can also enter the values manually.


The area bubbled in blue provides allowable stress modification factors that you can specify. Please note that CF or CV values are automatically filled in. CF values are determined from the size and stress grade of the member (No. 1 and Utility grades have different values). CV values are calculated when a glu-lam section is specified.  Note that this section allows for the specification of the Repetitive Member factor.  If the Repetitive Member factor option is selected, the program then offers the option to specify a value for the Wall Stud Repetitive Member Factor as defined by the NDS Special Design Provisions for Wind and Seismic (SDPWS).  If the option is selected to specify a Wall Stud Repetitive Member Factor, it will only be applied to load combinations that include wind.  Be sure to review the appropriate section of SDPWS for requirements on the use of this factor, as well as the values to be used for various sizes of dimension lumber.


The area in green provides quick access to the built-in wood section database. Simply click the button of the section type and the list on the right will be populated automatically from the appropriate database. Then just click on a section to have its data loaded into the entries in the red area.




Note:  The flat use factor will only be applied if it is specified by the user.  In addition, it is important to understand how the factor will be applied in situations where built-up columns are designed.  The flat use factor is supposed to be applied when bending occurs about the weak axis of the individual laminations.  But the program does not actually understand the orientation of individual laminations in a built-up column as of July 2018.  So for consistency, the program is set up to look at the overall dimensions of a built-up column cross section, and then to apply the flat use factor only when considering bending about the overall weak axis.  This requires the designer's consideration, because the weak axis of the overall built-up section may or may not correspond to the weak axis of the individual laminations.


Results Tab

This tab provides a summary of the stress ratios, reactions and deflections for the column.


Max Axial + Bending Stress Ratio is the governing load combination for the column. Listed is the governing load load combination, the NDS formulas that is used and the location of the maximum stress ratio above the base of the column. Please note maximum stress ratio is what is being reported because it governs the design.....not necessarily the highest axial or bending stress.


Max Shear Stress Ratio will probably never govern for a column design but is presented here with the governing load combination, location and allowable/actual stress values.


Lateral Load Reactions and Deflections are the result of applied lateral loads.




Design Maximum Combinations Tab

This tab lists the resulting maximum stress ratios for each load combination. This list is created by examining the detailed list (on the next tab) and determing the governing stress ratios for each load combination.




Detailed Results Tab - Stress

This tab lists the detailed results at small increments along the height of the column for each load combination. For consistency, all of the column headings use labels directly from the NDS code.


Note! This list scrolls to the right to display more information. See the successive screen captures below:




 Scroll a little to the right....


         And a little more....


                 And more still....


                         And then the final data column.....



Detailed Results Tab - Deflections

This tab reports the deflections at incremental locations along the height of the column, for each service load condition (i.e. for individual load cases and for a set of built-in service load combinations), along each axis. It is important to understand that the deflection values indicated on this tab represent RELATIVE deflections. That is, they represent the distance from the deflected shape of the column to a straight-line chord drawn between the deflected locations of the top and bottom nodes of the column. This has significance when viewing the deflection data for a column that is fixed at the bottom and free to deflect at the top. If lateral loads are applied to this type of cantilevered column, it is reasonable to expect that the free top will deflect laterally.  However, when viewing the results on the Service Load Deflections tab, the deflection at both the bottom AND the top will always be reported as zero, because this tab is reporting RELATIVE deflections, and by definition, the relative deflection of either endpoint of a member is zero. Do not interpret the results on the Service Load Deflections tab as ABSOLUTE deflections.  




End Reactions Tab

This tab provides the sideways (non-axial) reactions for individual load cases and for a set of built-in service load combinations, along each axis.



Sketch Tab



Axial-Shear-Moment Diagrams

This tab provides comprehensive charting capability to view graphs of Axial load, Shear, Moment, and Deflection along the length of the member. Note that the graphs are oriented such that the right end of the graph represents the column base, and the left end of the graph represents the column top. This was done to maximize the scale of the graph based on the screen area available.




Pn-Pnx-Mny Diagrams

This tab allows you to see the moment capacities about each axis given a certain allowable axial load.


This is mostly for reference and can be considered a reverse application of the load capacity calculations.


In the screen capture below we have selected a 30 degree angle. For a 1.1 kip axial load you can see the moment capacity values, Mnx and Mny.