Need Advice on Repairs to Bridge
- Thread starter Gizzy
- Start date
FatherMcD
Registered
My two cents...it looks like it was only the gussets that bent. I would try to gently pull it back into position then take a look at how the gussets fared. Those that look to be too damaged could then be replaced. Use a length of lumber flat against the right side to spread the strain as you pull it back into position. I would clamp on the right side toward the top of the bridge (in the picture) and pull the end closest to the camera toward the left bracing against a length of lumber clamped along the bottom on the left. The lumber on the left needs be small enough to allow the bridge to be pulled slightly beyond vertical so that it will rebound to vertical when the pull is released. Make the lumber as long as will fit in the space available to spread the load. You might find it straightens with minimal damage. Probably would help is there was a convenient grandchild in the teens to handle the grunt work.
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playmofire
Registered
I think that as well as the bend to one side there may be twisting at the base of the struts nearest the camera and that may be difficult to sort out.
viaEstrecha
Spanish metre gauge in G scale (on the cheap)
I had one very similar, given to me very bent and battered, I had to disassemble it but having done so, the sides flattened out fairly well (by hand manipulation and light hammering as it is very soft). To disguise the inevitable imperfections and add strength, I bolted strips of 10mm PVC equal angle and some other profile to the outside of the struts and painted it all with Hammerite. Not a particularly good shot from about 2008:
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korm kormsen
Registered
what Ken and Martyn said, plus stiffening the right angles.
if you got a tool for pop-rivets, and can find some Meccano pieces - then i would rivet diagonals to the verticals and the horizontals that connect the two sides, to create right angled triangles.
if you use "six-hole" lengths of meccano, the perfile even for the biggest rolling stock should be undisturbed.
if you got a tool for pop-rivets, and can find some Meccano pieces - then i would rivet diagonals to the verticals and the horizontals that connect the two sides, to create right angled triangles.
if you use "six-hole" lengths of meccano, the perfile even for the biggest rolling stock should be undisturbed.
As has mostly been said, much of it looks to be Ally, bending the bent bits back to shape once dismantled as Martyn says should be pretty easy. Deconstruction may be a bit of a job with rusty screws, a good dose of penetratingboil left for a day or two should help withbthat. Put the screes in a box till you reconstruct it so none are list. If you need help I have a pop riveter and could come over to wield it if needed.
Personally I would drill out all the rivets along the top and bottom sections so you end up with four sections. I would then tap straight with a hammer, then rebuild with new rivets. Job done ✔
Rhinochugger
Retired Oik
Bearing in mind that I am devout bodger, you could try taking it away from his sensitive eyes, and lean on it in the opposite direction. Aluminium does give a little bit
Just waiting for the same when the A428 duelling done from Black Cat to Caxton.
FatherMcD
Registered
Any information on how they straightened it out? Just in case, you know, someone else might have a similar problem in the future. (Asking for a friend)
Gizzy
A gentleman, a scholar, and a railway modeller....
No, none at all, but I guess the garage has a body shop and someone with the skills required for metal working....
Rhinochugger
Retired Oik
Gerard
Registered
From an engineering point here are some remarks to explain the behaviour of this steel bridge when it was overloaded.
Also how to find the critical beams and nodes and how to reload the structure in order to reshape (rebend) it:
1 Identify triangle beam structure shapes, they are much stronger than parallel and square beam structure shapes. This is because of the fact that a triangle shape can only be changed with a change in length of the beams. For changing the length of a beam a much much higher force is needed than for bending a joint of beams in a parallel or square shape of beams.
2 Identify flat beams , their function is to transfer pulling forces only. They will not bend when pulled. But they do bend when pushed. See the flat beams at the left-back side of the bridge., they are clearly slightly bended showing that they were experiencing a pushing force after the overload.
3 Identify L or T-shapes beams: there function is to transfer pushing and pulling forces. The L or T shape give the beams extra stiffness so they can handle high pushing forces before they start to bend aside. The latter is called "Buckling".
4 Identify the easy to bend parts of the structure. In this case these are all the vertical connection plates at top and bottom of the vertical L or T shapes beams.
5 Identify any buckled L or T shaped beams by extreme high pushing forces. In this case luckily there appears to be not one buckled L or T shaped beam.
6 Note that the top of the bridge is a square shaped parallel L shaped beam structure. It looks that this structure is still square shaped, but it is probably not. This is because of the fact that the ends of the front and back beams of the top structure are each connected to a vertical stiff triangle beam shape that keeps the end beam of the top parallel to the baseplate-end of the bridge. Luckily the connections in the top structure are made by one bolt per joint, so the forced rotation of these connections caused no damage and can be reversed easily.
So far the description of the structure and the analysis of the damage and possible forces that caused the damage.
7 Now ,given the information of the steel structure behaviour above, try to locate the point where the heavy overload did hit the structure and caused serious overload damage on the structure. This is important to know since we have to apply a similar reverse force to rapair the shape of the structure.
8 In this case apparently the end of the top of the bridge at camera side is moved aside by an overloading force.
9 The vertical beams are not buckled, so any extra weight force from above apparently did not result in any damage.
This leads to the conclusion that the force that caused the damage was in a horizontal direction.
10 To repair the bridge we have to apply a horizontal force facing left , while keeping the base and the backside of the bridge in a sturdy fixed position.
11 Now all the bends of the vertical plates have to be rebend properly. This must be carefully checked and if necessary the re- bending must be assisted step by step using two proper pliers, one on the vertical side of the top beam and one on the side of the vertical beam. The main objective here is to keep the vertical sides of the top and bottom beams in a vertical position in order to prevent them to bend aside.
So far my analysis.
I hope it helps you all when repairing steel structures.
Bart van der Schrieck
Also how to find the critical beams and nodes and how to reload the structure in order to reshape (rebend) it:
1 Identify triangle beam structure shapes, they are much stronger than parallel and square beam structure shapes. This is because of the fact that a triangle shape can only be changed with a change in length of the beams. For changing the length of a beam a much much higher force is needed than for bending a joint of beams in a parallel or square shape of beams.
2 Identify flat beams , their function is to transfer pulling forces only. They will not bend when pulled. But they do bend when pushed. See the flat beams at the left-back side of the bridge., they are clearly slightly bended showing that they were experiencing a pushing force after the overload.
3 Identify L or T-shapes beams: there function is to transfer pushing and pulling forces. The L or T shape give the beams extra stiffness so they can handle high pushing forces before they start to bend aside. The latter is called "Buckling".
4 Identify the easy to bend parts of the structure. In this case these are all the vertical connection plates at top and bottom of the vertical L or T shapes beams.
5 Identify any buckled L or T shaped beams by extreme high pushing forces. In this case luckily there appears to be not one buckled L or T shaped beam.
6 Note that the top of the bridge is a square shaped parallel L shaped beam structure. It looks that this structure is still square shaped, but it is probably not. This is because of the fact that the ends of the front and back beams of the top structure are each connected to a vertical stiff triangle beam shape that keeps the end beam of the top parallel to the baseplate-end of the bridge. Luckily the connections in the top structure are made by one bolt per joint, so the forced rotation of these connections caused no damage and can be reversed easily.
So far the description of the structure and the analysis of the damage and possible forces that caused the damage.
7 Now ,given the information of the steel structure behaviour above, try to locate the point where the heavy overload did hit the structure and caused serious overload damage on the structure. This is important to know since we have to apply a similar reverse force to rapair the shape of the structure.
8 In this case apparently the end of the top of the bridge at camera side is moved aside by an overloading force.
9 The vertical beams are not buckled, so any extra weight force from above apparently did not result in any damage.
This leads to the conclusion that the force that caused the damage was in a horizontal direction.
10 To repair the bridge we have to apply a horizontal force facing left , while keeping the base and the backside of the bridge in a sturdy fixed position.
11 Now all the bends of the vertical plates have to be rebend properly. This must be carefully checked and if necessary the re- bending must be assisted step by step using two proper pliers, one on the vertical side of the top beam and one on the side of the vertical beam. The main objective here is to keep the vertical sides of the top and bottom beams in a vertical position in order to prevent them to bend aside.
So far my analysis.
I hope it helps you all when repairing steel structures.
Bart van der Schrieck