Relationship between Beam Section Depth and Bending Moment

In summary, the conversation discusses two universal beams with different depths and flange widths, but no information is given about their span. The question asks for the bending moment capacity of the 500mm deep beam, but without knowing the span, this cannot be calculated. The conversation also mentions the relationship between bending stress and section depth, and clarifies the difference between bending moment and bending moment capacity. The answer to the question may involve using the equation Sy = M1*y1/I1 = M2*y2/I2, but more information is needed to solve it.
  • #1
joeykeys
11
0
Ok. There are 2 universal beams. One is 500mm deep and the other one is 400mm deep. For both beams, the top and bottom flanges are 200mm wide x 10mm deep. [SPAN of the beams is not given]

Questions is..If the maximum bending moment capacity of the 400mm deep universal beam is 200 kn.m. What is the bending moment capacity of the 500mm deep beam?

What i think is that beam's bending moment has nothing to do with its section depth is it?
So the answer to the question would be "Cannot be calculated since both the span measurement is not given."

Or there are other answers to this?

Thanks.
 
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  • #2
What on Earth are you studying?
 
  • #3
Bending stress is roughly proportional to the square of the section depth.
 
  • #4
joeykeys said:
r
Questions is..If the maximum bending moment capacity of the 400mm deep universal beam is 200 kn.m. What is the bending moment capacity of the 500mm deep beam?

What i think is that beam's bending moment has nothing to do with its section depth is it?
Are you confusing 'bending moment' with 'bending moment capacity'? The former is a function of loading, span, end conditions, etc. while the latter is a function of the beam's material properties and cross sectional shape.
 
  • #5
I'd guess is that the answer they want is something along the lines of

Sy = M1*y1/I1 = M2*y2/I2

where you know M1, y1, I1, y2, I2, and can rearrange the above to find M2.
 

1. What is the relationship between beam section depth and bending moment?

The relationship between beam section depth and bending moment is that as the depth of the beam section increases, the bending moment capacity of the beam also increases. This is because a deeper beam section has a larger moment of inertia, which allows it to resist bending forces more effectively.

2. How does the shape of the beam section affect the bending moment?

The shape of the beam section also affects the bending moment capacity. A beam with a wider flange, such as an I-beam, will have a higher moment of inertia and therefore a higher bending moment capacity compared to a beam with a narrower flange, such as a rectangular beam.

3. Is there a maximum depth for a beam section to achieve optimal bending moment capacity?

Yes, there is a maximum depth for a beam section to achieve optimal bending moment capacity. This is because as the depth of the beam section increases, the weight of the beam also increases, which can lead to structural inefficiencies and increased cost. Therefore, a balance must be struck between depth and cost to achieve the most efficient beam section for a given bending moment.

4. How does the material of the beam section affect the relationship between depth and bending moment?

The material of the beam section also plays a role in the relationship between depth and bending moment. Different materials have different strengths and elastic moduli, which can affect the bending moment capacity of a beam. For example, a steel beam will have a higher bending moment capacity compared to a wood beam of the same size and shape.

5. Can the relationship between beam section depth and bending moment be used to design a beam?

Yes, the relationship between beam section depth and bending moment is an important factor in beam design. Engineers use this relationship, along with other design considerations such as loading and support conditions, to determine the optimal beam section for a given application. It is an essential aspect of structural design to ensure the safety and stability of a structure.

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