ASDIP WOOD is a structural engineering software for design of wood members. It includes a module for Diaphragm Design based on the latest NDS and SDPWS provisions, which calculates the design shear strength of the diaphragm, as well as the adjusted design values for the required types of stresses of the tension and compression chords.
But how do you enter the information in the program? How do you check the results? How do you optimize the design in a real-life example? The following is a step-by-step wood diaphragm design example using ASDIP WOOD.
Wood diaphragm example
As an example, consider the rectangular wood diaphragm shown below, whose dimensions between lateral supports are 48'-0" long x 20'-0" wide. The wood panel is subject to a uniformly distributed lateral load of 100 plf due to wind and 100 plf due to seismic. The chord members are sawn lumber. Assume dry service conditions and normal temperature range. Find out the diaphragm shear capacity and design the chord members.
Diaphragm geometry
In the Diaphragm tab enter the diaphragm dimensions given in the statement of the problem, in this case W = 20'-0" and L = 48'-0". For now, let's assume a 5/16" structural panel with 6d nails spaced at 6" at both boundary and other edges. The panels are blocked. This panel can be selected from the built-in database. The shear capacity of this panel is 530 plf, as shown below.
The At-a-Glance tab shows a summary of the results, with the most important information, for a quick overview of the design. If a deficiency is identified, it can be further investigated in the other reports which offer a more detailed information.
Sawn lumber chord geometry
In the Chords tab enter the chord dimensions. Note that the chord is laterally supported at midspan in the weak axis, so Kx = 0.5. Select Sawn Lumber as the column type and in Species Region select Southern Pine. Let's try a 2-ply 2x8 section size from the database, as shown below.
The Condensed tab shows a condensed presentation of the results, grouped by topic, for a more in-depth overview of the design. If a deficiency is identified, it can be further investigated in the Detailed report, which offers a more detailed information.
Specifying the material properties
In the Materials tab specify the chord material properties. Click on the Select from Database button to show the corresponding table of products from the manufacturer. Dense Select Structural grade will be used in this example. The program will transfer the material properties to the template.
ASDIP WOOD generates a detailed presentation of the results in the Detailed tab, showing step-by-step calculations organized by topic and load combination, with exposed formulas and references to the NDS code. This is excellent for a deep granular check of the design.
Entering the applied loads
Use the Loads tab to enter the applied lateral loads to the diaphragm. In this case the loads are given in the statement of the problem as wind and seismic uniform loads. Specify ASD as the design method.
The program shows a graphical view of the interaction diagram of both, tension and compression chords. The points representing the loads are inside the usable area of the diagram, therefore the structural capacity is adequate.
Optimizing the design
The program calculates the shear strength of the diaphragm based on the specified frame / sheathing / nailing configuration. This shear strength is compared versus the maximum shear produced by the applied loads. In this example the seismic load is controlling the design, with a shear ratio of 0.44.
The software calculates the tension and compression chord forces, then calculates the adjustment factors for the different design conditions per the NDS. These factors affect the reference design values for the specified material. In this example the seismic compression ratio is 0.14. Further optimization can be achieved by selecting other preferred sections easily from the database.
Takeaway
ASDIP WOOD includes the design of wood diaphragms and chord members. This step-by-step design example shows how fast the design can be completed and optimized using ASDIP WOOD. The results are shown instantly in both text and graphics format for an immediate granular check.
For our collection of blog posts about concrete design please visit Structural Wood Design.
Detailed information is available about this structural engineering software by visiting ASDIP WOOD. You are invited to download the Free 15-day Software Trial, or go ahead and Place your Order.
Best regards,
Javier Encinas, PE
ASDIP Structural Software
Are you planning to offer more complex diaphragm analysis soon? Diaphragm shapes that are not just rectangular; unconventional shapes, diaphragm openings, etc.