Maximum deflection in a timber beam

In summary, the conversation discusses the calculation of the maximum deflection (in mm) of Radiata pine VSG8 timber joists supporting particle board flooring with a dead load of 8 kg/m2 and an imposed load of 3.5 kPa. The formula for maximum deflection is provided, but the value of "I" needs to be determined. The question also mentions an earlier calculation of the UDL using w= 1.2*dead + 1.5*live, which may need to be used in the calculation.
  • #1
nick.w
3
0

Homework Statement


Particle board flooring (dead load 8 kg/m2 including joist self-weight) is supported by a series
of Radiata pine VSG8, of call size 150 x 50, timber joists running parallel to one other at 450
mm centers and spanning L=3.8 m between supports. The floor supports an imposed load
of 3.5 kPa.
http://img14.imageshack.us/img14/7767/timbertable.png [Broken]

Assuming strength requirements are OK (they may or may not be), what would be the
maximum deflection (in mm) of the joist?
Assume allowable deflection for the joist is L/350. Is the calculated deflection
acceptable?

NOTE: for this calculation use w = 1.0 * Dead + 1.0 * Live
(use gauged, kiln dried section size for timber section)

Homework Equations



Max Deflection = 5wL4 / (384EI)For the above formulae:
L is the length of the beam,
E is Young’s Modulus (Units Pa, MPa, GPa)
I is the Second Moment of Area of the cross-sectional shape of the beam (units m4 or mm4)

The Attempt at a Solution



I think this is the correct formula but need to be certain. Also how do I find "I" if this is the correct forumla.

I also get thrown off by. "use w = 1.0 * Dead + 1.0 * Live" as I have already calculated the UDL in an earlier part of the question using w= 1.2*dead + 1.5*live.

If you guy could point me in the right pirection of which formula to use I would appreciate it.

Regards,
Nick
 
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  • #2
edit: Just been having a flick through the forums and wondering if I might of put this in the wrong place. Please move if so. Cheers
 
  • #3
bump? More info needed?
 

1. What is maximum deflection in a timber beam?

The maximum deflection in a timber beam refers to the maximum amount of bending or displacement that a beam can experience before it breaks or becomes unstable. This measure is important in determining the load-bearing capacity of a timber beam.

2. How is maximum deflection calculated in a timber beam?

Maximum deflection in a timber beam is calculated by using the formula: D = (WL^3)/(48EI), where D is the maximum deflection, W is the load applied, L is the length of the beam, E is the modulus of elasticity, and I is the moment of inertia. This formula takes into account the material properties of the timber beam and the applied load.

3. What factors affect maximum deflection in a timber beam?

Several factors can affect the maximum deflection in a timber beam, including the type and quality of the timber, the size and shape of the beam, the type and distribution of the load, and the span of the beam. Additionally, environmental factors such as temperature and moisture can also impact the deflection of a timber beam.

4. Why is it important to consider maximum deflection in timber beams?

Maximum deflection is an important consideration in timber beam design as it directly affects the structural integrity and stability of the beam. If a beam experiences excessive deflection, it can lead to failure or collapse, posing a safety hazard. By understanding the maximum deflection, engineers and builders can ensure that the beam is strong enough to withstand the expected load without compromising its structural integrity.

5. How can maximum deflection in timber beams be minimized?

To minimize the maximum deflection in timber beams, engineers and builders can consider using stronger and stiffer timber, increasing the beam's size or shape, reducing the span, and evenly distributing the load. Additionally, proper installation and regular maintenance can also help to prevent excessive deflection in timber beams.

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