Glulam Beam & Column Design Software

1. Decoding the “Stress Classes”

US Glulam grades can be confusing “alphabet soup.” Our calculator simplifies the NDS Supplement Table 5A library:

• 24F-1.8E / 24F-V4: The industry standard for Western Species (Douglas Fir-Larch). “24F” means 2400 psi bending stress; “1.8E” is 1.8 million psi stiffness.
• 24F-V8 (Balanced): Specific layups for continuous span beams or cantilevers where negative bending strength must match positive bending.
• Southern Pine (24F-V3): High-strength layups common in the Eastern US.
• Custom Layups: Define your own specific combination to match a manufacturer’s submittal.

2. The Volume Factor ($C_V$)

In the NDS, Glulam behaves differently than Sawn Lumber. The “Size Factor” ($C_F$) is replaced by the Volume Factor ($C_V$).

$$C_V = \left(\frac{21}{L}\right)^{1/x} \cdot \left(\frac{12}{d}\right)^{1/x} \cdot \left(\frac{5.125}{b}\right)^{1/x}$$

This formula penalizes large-volume beams. Our tool calculates this dynamically based on your span and cross-section, ensuring you don’t overestimate the capacity of massive girders.

3. Beam Stability ($C_L$)

For deep, narrow beams, Lateral Torsional Buckling is a risk.

The calculator determines the Slenderness Ratio ($R_B$) based on your unbraced length ($l_u$) and computes the Beam Stability Factor ($C_L$).

• Optimization Tip: Toggle “Continuous Decking Restraint” to set $C_L = 1.0$ and maximize your beam’s efficiency.

Adjusted Design Values ($F’$):

The calculator applies the full suite of NDS modification factors to the Reference Design Values:

$$F’_b = F_b \cdot C_D \cdot C_M \cdot C_t \cdot C_L \cdot C_V$$

(Note: $C_V$ and $C_L$ are not cumulative for bending; the NDS requires using the lesser of the two factors).

Load Duration ($C_D$):

Adjusts strength based on the shortest-duration load in the combination:

• $C_D = 1.6$: Wind/Seismic (Short Term)
• $C_D = 1.0$: Live Load (Ten Years)
• $C_D = 0.9$: Dead Load (Permanent)

Deflection & Creep:

For Total Load deflection, the tool applies the creep factor ($K_{cr}$):

$$\Delta_{Total} = K_{cr} \cdot \Delta_{LongTerm} + \Delta_{ShortTerm}$$

• $K_{cr} = 1.5$ for Glulam (Note: This is lower than the $2.0$ used for Sawn Lumber, reflecting Glulam’s seasoned stability).