Find reactions at supports and bending/shear/axial diagrams

In summary: Remember, the frame as a whole remains static, so the individual members must be static as well. Thanks for your reply! Before I proceed, I want to make sure something.In my calculation for the left body, I resolve vertical reaction into two components. One is used to find out the shear force and one is the axial force along the beam.Is my concept here correct? If this is the case, how do I balance Rh here?
  • #1
gacb17424
2
0

Homework Statement


0aac393504.png

Force by uniform loading = 20(5) = 100kN
Vertical component of the uniform loading = 20(5)(3/5) = 60kN
Horizontal component of the loading = 20(5)(4/5) = 80kN
vertical reaction at roller support = Vr
vertical reaction at pin support = Vp

Homework Equations


Fx=0, Fy=0, M=0

The Attempt at a Solution



Finding reactions[/B]
Horizontal reaction is only at pin support. Let it be Hp. As Fx=0
Hp=80-40=40kN (to the left)
So I take moment at pin support first so as to find out Vr
Vr=[40(1)+50(3)+60(7.5)-80(2)] / 9 = 160/3 kN (upwards)
take moment at roller support to find Vp
Vp=[100(2.5)+50(6)-40(1)] / 9 = 170/3 kN (upwards)

Attempt to find out the equations for diagrams
for the left part of the frame (free body)
9f4498861d.jpg

Resolving Vr into two component
let the one perpendicular to frame be Rp, Rp = 32 kN
the other one along the frame be Ra, Ra = 128/3 kN
distance from roller be x
Axial force = Ra = 128/3 kN
Shear force = 32-20x,
M=32x-10x2

But for the middle part and right part of the frame, how do I consider the free body? and the segments divided by the point loading?
I tried thinking to cut at the top-right corner to consider the right part of the frame as a free body but then what should I do for the segment between the P2 loading and the corner?
The middle part is even more messy to me.
Thanks!
 
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  • #2
The idea behind the free body is that you can separate a particular member from the rest of the structure as long as you include the loads at the ends as well as any loads applied directly to that member.

You've started your calculation of the reaction forces and moments with the sloped member on the left of the frame. Figure out which loads from the sloped member are transmitted into the top member, thence to the vertical member on the RHS of the frame.

Remember, the frame as a whole remains static, so the individual members must be static as well.
 
  • #3
SteamKing said:
The idea behind the free body is that you can separate a particular member from the rest of the structure as long as you include the loads at the ends as well as any loads applied directly to that member.

You've started your calculation of the reaction forces and moments with the sloped member on the left of the frame. Figure out which loads from the sloped member are transmitted into the top member, thence to the vertical member on the RHS of the frame.

Remember, the frame as a whole remains static, so the individual members must be static as well.
Thanks for your reply! Before I proceed, I want to make sure something.
In my calculation for the left body, I resolve vertical reaction into two components. One is used to find out the shear force and one is the axial force along the beam.
Is my concept here correct? If this is the case, how do I balance Rh here?
a6bd24c976.jpg
 
  • #4
gacb17424 said:
Thanks for your reply! Before I proceed, I want to make sure something.
In my calculation for the left body, I resolve vertical reaction into two components. One is used to find out the shear force and one is the axial force along the beam.
Is my concept here correct? If this is the case, how do I balance Rh here?
a6bd24c976.jpg

You've calculated the reactions on the sloped member in a coordinate system which is aligned with that member. What you need to find is how these forces are transmitted into the other member(s)of this frame. IOW, you need to find the components of the forces which are aligned with the other member attached to the sloped member.
 

What is the purpose of finding reactions at supports?

Finding reactions at supports is an essential step in analyzing and designing structures. It helps determine the forces and moments that the supports must withstand, which is crucial for ensuring the stability and safety of the structure.

How are reactions at supports calculated?

Reactions at supports are calculated using the principles of statics, which state that the sum of all forces and moments acting on a body must equal zero for it to be in equilibrium. This can be achieved by applying the equations of equilibrium, which include the sum of forces in the x and y directions, as well as the sum of moments about any point.

What is the significance of bending, shear, and axial diagrams?

Bending, shear, and axial diagrams are graphical representations of the internal forces and moments that act on a structure. These diagrams are essential for understanding the structural behavior and determining the critical sections of a structure.

How are bending, shear, and axial diagrams constructed?

Bending, shear, and axial diagrams are constructed by first determining the internal forces and moments at different sections of the structure. These values are then plotted on the appropriate axes, with the bending moment and shear force diagrams typically shown as continuous lines and the axial force diagram shown as a series of discrete points.

What is the difference between positive and negative bending moments?

Positive bending moments occur when the top of a member is in compression and the bottom is in tension, while negative bending moments occur when the top of a member is in tension and the bottom is in compression. These moments can have significant effects on the design and behavior of a structure, and must be carefully considered in the analysis process.

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