Web openings in beams are sometimes required to pass pipes or other utilities through the structural members. Under the presence of shear and moments, the design of web openings may be time-consuming. This document shows a step-by-step web opening example using ASDIP STEEL software.
Web Opening Example
As an example, consider the 40-ft span composite beam shown below. The beam size is W18x60 and it's subject to two concentrated loads at the third points of the span. The concrete slab is 5-1/2" thick on a 3" metal deck. Design a 10"x24" web opening at the location 2-2 shown below.
Web Opening Example Input
Enter the information given in the statement of the example. Go to the Geometry tab and select the beam size W18x60 from the database. Then specify the opening size and the slab dimensions.
Use the Materials tab to enter the material properties, such as the concrete and steel strengths. In this case use A36 steel for the beam and plate, and f'c = 4 ksi for the concrete slab. Finally, go to the Loads tab and enter the factored shear am moment at the location of the web opening. In this example, for the location 2-2 at the end third of the span, Vu = 45 kip and Mu = 300 k-ft.
Web Opening Example Output
The At-a-Glance tab shows a summary of the design for a quick overview of your work as you go. The green check marks indicate that the checks passed. The Condensed tab shows a condensed set of calculations with the most important information grouped by topic for a more in-depth check. The Detailed tab shows a step-by step detailed set of calculations with exposed formulas and references to the design code.
In this example, the structural capacity of the beam with the unreinforced opening was 18% overstressed, therefore a reinforcement was necessary. Several combinations of plate width and thickness would work, so a plate 1-1/2"x 3/8" at one side of the web was selected. The final shear-moment interaction ratio is 0.95, so the structural capacity is adequate to resist the design loads. The screenshot above shows graphically the location of the loads in the usable area of the interaction diagram.
In addition, the program performs multiple design checks required by the code, such as geometric limitations of the opening and the resulting top and bottom tees, compression flange local buckling, maximum shear capacity, and local buckling of the reinforcement plate. All the design checks pass with the selected reinforcement, therefore the design is adequate as shown below.
ASDIP STEEL includes the design of web openings, with multiple options to model and optimize the design easily. This web opening example shows that the design can be completed and optimized using ASDIP STEEL in minutes.
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Javier Encinas, PE
ASDIP Structural Software