Designing an LVL Beam: A Step-by-Step Guide for Span Tables

When designing a structural element, such as a laminated veneer lumber (LVL) beam, it is essential to consider various factors that affect its load-carrying capacity. In this article, we will explore the importance of using span tables in conjunction with other calculations to ensure the proper sizing of an LVL beam.

Understanding Load-Flooring Values

When designing a structural element, engineers often rely on load-flooring values (PLF) to determine the required strength and size of the member. In this context, PLF represents the weight per square foot that the structure is designed to carry. For instance, if a structure is expected to support a live load of 10 pounds per square foot (PSF), the engineer would need to design the structural element accordingly.

Calculating Load-Flooring Values

In our example, we are dealing with a situation where the ceiling joists have two layers of drywall and mud, which adds up to a dead load of 5 PSF. Additionally, there is an attic space above with blow-in insulation that contributes another 2 PSF to the overall load. Moreover, there may be a live load of someone crawling around in the attic, which can add up to 10 PSF.

To calculate the PLF, we need to consider all these loads and add them together. In our example, the total dead load is 5 PSF + 2 PSF = 7 PSF, while the live load is 10 PSF. Therefore, the total PLF would be approximately 17 PSF.

Applying Span Tables

Now that we have calculated the PLF, we can use span tables to determine the required size and strength of the LVL beam. According to our calculations, the 'Span Carried' by the ceiling joists is 28 feet, but since the joists are not continuous, we need to halve this value to obtain a more accurate estimate.

Using a span table or a design software program, we can determine that for a PLF of approximately 17 PSF and a span of 14 feet (half the 'Span Carried' value), an LVL beam with a certain size and strength would be required.

Designing the LVL Beam

To ensure the proper sizing of the LVL beam, it is essential to consider various factors, including the type of lumber used, the spacing of the joists, and the load-carrying capacity of the member. By using span tables in conjunction with other calculations, engineers can design an LVL beam that meets the structural requirements of the project.

In this article, we have explored the importance of using span tables when designing an LVL beam for a specific application. By understanding load-flooring values and calculating the PLF, engineers can determine the required size and strength of the member. Furthermore, by applying span tables and considering various factors that affect the load-carrying capacity of the LVL beam, engineers can ensure the proper sizing of the structural element.

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