Calculating Moment and Deflection for Handrail Beam with Attached Bolt

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In summary, the question is about the moment and deflection calculation for a handrail beam. The handrail is 4" x 4" and attached with a bolt at the bottom, but not halfway. The question is whether to use the full 89mm or 89/2 in the section modulus and moment of inertia calculations. It has been confirmed that the calculation should use (89 - 38) = 51 mm and 0.5*51, as the 89 mm portion has little or no effect on the deflection.
  • #1
blackbird2552
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Hello everyone,

I have a question regarding the moment and deflection calculation of this handrail beam that I have. I am attaching a picture to give you guys a look at what I am working with.

The hand railing is 4" x 4" and it is not attached half way, its just resting on that beam, it is however attached with a bolt at the bottom. My question is, when I am looking for the resisting moment would I take 89/2 in the section modulus calculations or the full 89mm. Same goes for deflection, when I do the moment of inertia, would I do the full 89 mm or 89/2. If it is 89/2 then how would I incorporate the rest of the beam in the resisting moment/deflection or would it have no effect on it?

any help would be greatly appreciated, thanks!

http://tinypic.com/r/lzmh2/6
 
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  • #2
blackbird2552: In general, it appears you would use (89 - 38) = 51 mm, and 0.5*51, in the section modulus calculation, for the bending stress calculation. You would also use 51 mm in the moment of inertia calculation, for the deflection calculation. The 89 mm portion of the handrail beam would have little or no effect on the deflection.
 
  • #3
Thank you so much! that is exactly what i needed confirmed and also thanks for clearing up my concept.
 

FAQ: Calculating Moment and Deflection for Handrail Beam with Attached Bolt

1. What is the definition of "moment" in timber beam design?

The moment of a timber beam refers to the force that causes the beam to bend or deflect. It is a measure of the bending strength of the beam and is typically measured in units of pound-feet (lb-ft) or Newton-meters (N-m).

2. How is the moment of a timber beam calculated?

The moment of a timber beam is calculated by multiplying the force applied to the beam by the distance from the point of application to the point of support. This is known as the moment arm or lever arm. The formula for moment is M = F * d, where M is the moment, F is the force, and d is the distance.

3. What is the maximum allowable moment for a timber beam?

The maximum allowable moment for a timber beam depends on several factors, including the type of wood, the dimensions of the beam, and the type of load it will be subjected to. It is important to consult with a structural engineer or refer to building codes to determine the appropriate maximum moment for a specific timber beam.

4. How does moment affect the deflection of a timber beam?

Moment and deflection are closely related in timber beam design. As the moment increases, the deflection of the beam also increases. This is because a higher moment creates a greater bending force on the beam, causing it to deflect or bend more. Therefore, it is important to consider both moment and deflection when designing timber beams to ensure structural stability.

5. How can the moment and deflection of a timber beam be controlled?

The moment and deflection of a timber beam can be controlled by adjusting the dimensions of the beam, the type of wood used, and the placement of supports. Increasing the depth and width of the beam, using a stronger type of wood, and adding more supports can help to decrease the moment and deflection of the beam. Additionally, using reinforcement methods such as adding steel plates or gluing multiple beams together can also help to control moment and deflection.

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