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Calculate glued laminated timber beam capacity, size requirements, and structural properties
| Grade | Bending Stress Fb (psi) | Modulus of Elasticity (psi) | Description | Common Uses |
|---|---|---|---|---|
| 24F-1.8E | 2,400 | 1,800,000 | Premium Architectural | Exposed beams, high-end residential |
| 20F-1.5E | 2,000 | 1,500,000 | Standard Structural | Commercial, residential, agricultural |
| 16F-1.3E | 1,600 | 1,300,000 | Industrial Grade | Utility buildings, covered structures |
| 12F-1.0E | 1,200 | 1,000,000 | Utility Grade | Non-structural, temporary structures |
| Property | Glulam | LVL | Solid Sawn |
|---|---|---|---|
| Strength | Very High | Very High | Good |
| Appearance | Excellent | Industrial | Natural |
| Deflection | Low | Very Low | Moderate |
| Cost | Moderate | Moderate | Low |
| Durability | Excellent | Good | Moderate |
| Curved Beams | Yes | No | No |
| Availability | Good | Good | Excellent |
Glulam grades (e.g., 24F-1.8E) indicate the bending strength (F value, in psi) and stiffness (E value, modulus of elasticity in million psi). Higher grades have greater load capacity but higher cost. The most common grades are 24F-1.8E (premium), 20F-1.5E (standard), and 16F-1.3E (industrial).
Appearance grade affects visual quality and cost. Industrial grade has knots and color variation but is suitable for utility applications. Architectural grade provides better appearance for exposed beams. Premium grade offers the finest appearance for high-end visible applications. Cost multipliers: Industrial (1.0x), Architectural (1.25x), Premium (1.5x).
Yes, one of the major advantages of glulam is the ability to manufacture curved and arched beams. Curved beams can follow vault or dome profiles, and arched beams can support catenary and parabolic shapes. Curved glulam beams are commonly used in churches, sports facilities, and architectural applications.
Camber is an upward curve built into glulam beams to counteract deflection under load. A typical camber of 1.5 times the expected deflection helps keep the beam level or slightly upward under design loads. Proper camber improves appearance and can help with water drainage on roof beams.
Glulam connections typically use bolts, bearing plates, joist hangers, or welded steel plates depending on the application. Connection design is critical and must account for shear, tension, and bearing stresses. Common connections include simple supports on posts or walls and moment-resisting connections with steel plates. Connections should be designed by a structural engineer.
Load duration affects allowable stress. Standard (10 years) = 1.0x, Short-term (2 months) = 1.15x, Wind/earthquake = 1.33x, Impact = 2.0x. Roof loads often qualify for short-term duration (1.15x increase) since snow and wind don't load the beam continuously.
Connection design requires analysis of shear, tension, and bearing forces. For bearing on concrete or wood, ensure pressure doesn't exceed bearing capacity. For bolted connections, check bolt shear and member tensile capacity around holes. For welded connections, use structural steel with proper fillet welds. Professional engineering is recommended.
Beam size depends on load type, magnitude, and grade. For a roof with 100 psf (typical snow + dead load), a 20F-1.5E beam might be 5.125" x 18" to 21". A floor with 150 psf might need 6.75" x 24". Use this calculator to check specific sizes, but always consult a structural engineer for actual designs.
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