2 appended answer 25156 as supplemental
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My question may sound silly as it’s mainly good sense but I may be mixing things up.

Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other end. Let’s suppose a dead weight is put at the free end. This results in a bending moment at the fixed end of say 10 Nm and a given deflection at the free end of say 1 cm.

Now let’s suppose the beam thickness gets increased and as a result stiffer. The deflection at the tip will be reduced for sure, but what about the bending moment at the fixed end? Is making the beam more rigid going to reduce the bending moment?

Looking forward to your thoughts! Many thanks


Thanks for you answers, much appreciated.

I get that the bending moment caused by a static load applied at the free-end does not depend on the elasticity of the beam. Only the deflection does. I would have thought that the greater the deflection the higher the bending moment... Can you confirm this isn't true? Imagine a 100 m long vertical monopile support structure looking like a slender cylinder anchored in the seabed and subjected to dynamic wave loadings exciting all the cylinder modes. The thinner the cylinder wall is, the more elastic the cylinder gets and the greater the deflections at the top get. I would think that the maximum bending moment would be reached when the deflection is the most significant and therefore making the cylinder more rigid with thicker wall would both reduce the deflections and the max bending moment, wouldn't it?

My question may sound silly as it’s mainly good sense but I may be mixing things up.

Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other end. Let’s suppose a dead weight is put at the free end. This results in a bending moment at the fixed end of say 10 Nm and a given deflection at the free end of say 1 cm.

Now let’s suppose the beam thickness gets increased and as a result stiffer. The deflection at the tip will be reduced for sure, but what about the bending moment at the fixed end? Is making the beam more rigid going to reduce the bending moment?

Looking forward to your thoughts! Many thanks

My question may sound silly as it’s mainly good sense but I may be mixing things up.

Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other end. Let’s suppose a dead weight is put at the free end. This results in a bending moment at the fixed end of say 10 Nm and a given deflection at the free end of say 1 cm.

Now let’s suppose the beam thickness gets increased and as a result stiffer. The deflection at the tip will be reduced for sure, but what about the bending moment at the fixed end? Is making the beam more rigid going to reduce the bending moment?

Looking forward to your thoughts! Many thanks


Thanks for you answers, much appreciated.

I get that the bending moment caused by a static load applied at the free-end does not depend on the elasticity of the beam. Only the deflection does. I would have thought that the greater the deflection the higher the bending moment... Can you confirm this isn't true? Imagine a 100 m long vertical monopile support structure looking like a slender cylinder anchored in the seabed and subjected to dynamic wave loadings exciting all the cylinder modes. The thinner the cylinder wall is, the more elastic the cylinder gets and the greater the deflections at the top get. I would think that the maximum bending moment would be reached when the deflection is the most significant and therefore making the cylinder more rigid with thicker wall would both reduce the deflections and the max bending moment, wouldn't it?

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How does stiffness/rigidity affect the bending moment of a beam

My question may sound silly as it’s mainly good sense but I may be mixing things up.

Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other end. Let’s suppose a dead weight is put at the free end. This results in a bending moment at the fixed end of say 10 Nm and a given deflection at the free end of say 1 cm.

Now let’s suppose the beam thickness gets increased and as a result stiffer. The deflection at the tip will be reduced for sure, but what about the bending moment at the fixed end? Is making the beam more rigid going to reduce the bending moment?

Looking forward to your thoughts! Many thanks