Hello all

I was hoping someone could help with the following:-

I have a pin jointed truss (all members are joined by frictionless pins and load is only applied to the joints), supported by 2 x pin jointed supports.

If my pin jointed structure was loaded solely at a joint with 200kN which resulted in a vertical deflection of 22mm with a Youngs modulus of 150kN/mm^2.

If I then doubled the load to 400kN but kept everything else the same then what would happen to my deflection?

I think the vertical deflection will double from 22mm to 44mm - but how can I prove this with without detailed calculations?

I know that if I halved the young's modulus then this would be result in the deflection doubling.

Is there any other ways of proving that the deflection will double (assuming it does double)???

Thank you.

]]>I was hoping someone could help with the following:-

I have a pin jointed truss (all members are joined by frictionless pins and load is only applied to the joints), supported by 2 x pin jointed supports.

If my pin jointed structure was loaded solely at a joint with 200kN which resulted in a vertical deflection of 22mm with a Youngs modulus of 150kN/mm^2.

If I then doubled the load to 400kN but kept everything else the same then what would happen to my deflection?

I think the vertical deflection will double from 22mm to 44mm - but how can I prove this with without detailed calculations?

I know that if I halved the young's modulus then this would be result in the deflection doubling.

Is there any other ways of proving that the deflection will double (assuming it does double)???

Thank you.

Hello all

I was wondering if anyone could help explain how the Vertical reactions for the following structure were calculated.

P1.png

I am able to calculate the Horizontal reactions. It is the vertical reactions that I am struggling with.

I do the following:-

Sum Vertical Reactions = 0

Va + Vd - 230 = 0

If I take moments about D I get:-

Sum of Moments about Support D = 0

(5.4*230) + (Ha*1.8) = 0

Ha = -690kN

I just don't know how to calculate 230kN at support A.

Any advice?

Thank you.

I was wondering if anyone could help explain how the Vertical reactions for the following structure were calculated.

P1.png

I am able to calculate the Horizontal reactions. It is the vertical reactions that I am struggling with.

I do the following:-

Sum Vertical Reactions = 0

Va + Vd - 230 = 0

If I take moments about D I get:-

Sum of Moments about Support D = 0

(5.4*230) + (Ha*1.8) = 0

Ha = -690kN

I just don't know how to calculate 230kN at support A.

Any advice?

Thank you.

Hello all

I was wondering if someone could help me clear my understanding regarding the sign convention and terminology related to Bending Moment Diagrams.

The Sign Convention I have been told to use is:-

1) Tension on top means Negative Bending Moment, also called Hogging Moment.

2) Tension on bottom mean Positive Bending Moment, also called Sagging Moment.

I am simply trying to understand what this means in the context of my example below:-

BMD Example.PNG

1) My first question is that using my sign convention which BMD is correct the Blue or the Green?

2) The term Hogging and Sagging do they relate to the deflected shape of the beam (shown in Pink) or the shape of the bending moment diagram?

If anyone can help shed any light then that would be great.

Thank you.

I was wondering if someone could help me clear my understanding regarding the sign convention and terminology related to Bending Moment Diagrams.

The Sign Convention I have been told to use is:-

1) Tension on top means Negative Bending Moment, also called Hogging Moment.

2) Tension on bottom mean Positive Bending Moment, also called Sagging Moment.

I am simply trying to understand what this means in the context of my example below:-

BMD Example.PNG

1) My first question is that using my sign convention which BMD is correct the Blue or the Green?

2) The term Hogging and Sagging do they relate to the deflected shape of the beam (shown in Pink) or the shape of the bending moment diagram?

If anyone can help shed any light then that would be great.

Thank you.