CSA O86 Procedure for Joists of Any Material

For joists made from lumber, glulam, SCL or I-joist materials, the program allows you to use the procedure given in CSA O86 A.5.4.5 to compute an allowable vibration-controlled span length.

Inputs

In the Vibration Details dialog, you add information about the subfloor sheathing material, concrete or wood panel topping, and connection to the joists. I-Joist EI and EA values come from the WoodWorks database and can be modified in database Editor.

Allowable Span Increases

In the Vibration Details dialog, checkboxes are available for allowable span increase:

• 5% for lateral bracing
• 5% for gypsum board ceiling
• 20% effective stiffness EI_eff increase for multi-span end fixity effect

Only one of the two 5% increases are applied if both are selected , as per the O86 A5.4.5 Commentary.

As per A.5.4.5, the lateral bracing and multi-span inputs are unchecked and disabled if concrete topping is selected. The gypsum board input is unchecked and disabled if any topping is selected.

Span Length

In O86 A5.4.5, the span l is used in the following places:

• the adjustment in EI_joist to consider shear deflection,
• in ĒĀ₁ when there is topping,
• in the factors K_L and K_j leading to K_tss.

Given that this length is used to compute an allowable span length, which has a different symbol, l_v in O86, it is unclear from the what span length should be used. The use of the actual span length would lead to different allowable span lengths depending on the actual member lengths, and the generation of span tables would be indeterminate.

The CCMC Report method for I-joists says to iterate on the vibration-controlled span length Lv, recalculating until it converges to a value, and the same principle applies here, so Sizer calculates the vibration-controlled span length and uses it in the calculations for the next iteration, until the difference between iterations becomes very small.

Intermediate Calculation Output

Sizer has a Detailed Design Calculations report accessed from the main toolbar to show intermediate data used in the A.5.4.5 calculations. Any value in A.5.4.5 given a symbol like EIc or EA1bar is given in a hierarchical order corresponding to the calculation procedure. It shows the following information:

• Input data - input in the Vibration dialog and other data, such as the larges span, joist spacing, etc., relevant to the calculations.
• Material Properties - Information from tables O86 A.1 and A.2 such as sheathing EI and EA values, other values hard-wired into A.5.4.5 like the load-slip modulus s1, and values from the database like I-joist EI and EA.
• Equations - All the intermediate equations in A.5.4.5 are shown.
• Intermediate Data - The values are all in metric in mm and kN, as they are in A.5.4.5, even if Imperial is chosen as the unit system.