Constructing a Victorian Stone Viaduct

[Andy873]

I was curious as to how the Victorians built stone viaducts.

Have I got the following sequence more or less correct:

1. The abutments and piers / columns were constructed with the bases standing on / in solid rock.
2. Wooden arches are constructed and connect the piers together with supports.
3. Before the stone arches begin to be constructed the piers are reinforced,
4. The stone arches are then constructed and side walls added.
5. To complete the process, the to be track bed area (middle section) is infilled with rubble etc.
6. The temporary wooden arches a removed.

Whilst all this is ongoing embankments (if needed) are constructed either side on the abutments.
To finish off of course, ballast and track are added.

Questions please:
I'm presuming (something I hate doing!) that all the temporary wooden arch bases would be in place before you started to build the sides of the stone arches?

Would you build one stone arch then move onto the next? or were the arches built up in tandem spreading the load on the piers?

Would the individual stone pieces be cemented together or just fit into place?

I've hear mention of a viaduct "Spring point" - what's that please?

 

[swt_passenger]

I was curious as to how the Victorians built stone viaducts.

[…]

I've hear mention of a viaduct "Spring point" - what's that please?

AIUI that’s ‘springing point’ where the inner vertical face of the column changes into the inside of the curve of the arch. I’ve seen the term used when brick arches are reconstructed for gauge clearance, they often refer to demolition “down to“ the springing point, which is where they often fit a cast concrete slab.

 

[eastwestdivide]

viaduct "Spring point"

Springing point - in other words where the arch springs from

 

[Andy873]

AIUI that’s ‘springing point’ where the inner vertical face of the column changes into the inside of the curve of the arch. I’ve seen the term used when brick arches are reconstructed for gauge clearance, they often refer to demolition “down to“ the springing point, which is where they often fit a cast concrete slab.

Springing point - in other words where the arch springs from

Thanks for clearing that up for me!

Based on several Victorian viaducts I've drawn one being constructed at several stages. This is a sandstone one despite the colour I've drawn it. The temporary wood arches are in yellow, what does anyone think? any good? see attached.

 

[edwin_m]

I was curious as to how the Victorians built stone viaducts.

Have I got the following sequence more or less correct:

1. The abutments and piers / columns were constructed with the bases standing on / in solid rock.
2. Wooden arches are constructed and connect the piers together with supports.
3. Before the stone arches begin to be constructed the piers are reinforced,
4. The stone arches are then constructed and side walls added.
5. To complete the process, the to be track bed area (middle section) is infilled with rubble etc.
6. The temporary wooden arches a removed.

Whilst all this is ongoing embankments (if needed) are constructed either side on the abutments.
To finish off of course, ballast and track are added.

Questions please:
I'm presuming (something I hate doing!) that all the temporary wooden arch bases would be in place before you started to build the sides of the stone arches?

Would you build one stone arch then move onto the next? or were the arches built up in tandem spreading the load on the piers?

Would the individual stone pieces be cemented together or just fit into place?

I've hear mention of a viaduct "Spring point" - what's that please?

Bit in bold - how do you believe the piers are reinforced? I would expect once they are built they would be able to support the structure. The structure around the springing point is designed to have some protruding feature to support the wooden formwork.

One thing to bear in mind is that if the arch is constructed on one side of a pier and not the other, then there is an unbalanced lateral force that might topple the pier. So I imagine groups of arches would be constructed simultaneously. Some viaducts, such as Ribblehead, have some of the piers wider, which is probably so the arches one side of this could be built first rather than having every single arch under construction at the same time.

 

[swt_passenger]

Bit in bold - how do you believe the piers are reinforced? I would expect once they are built they would be able to support the structure. The structure around the springing point is designed to have some protruding feature to support the wooden formwork.

One thing to bear in mind is that if the arch is constructed on one side of a pier and not the other, then there is an unbalanced lateral force that might topple the pier. So I imagine groups of arches would be constructed simultaneously. Some viaducts, such as Ribblehead, have some of the piers wider, which is probably so the arches one side of this could be built first rather than having every single arch under construction at the same time.

There’s a good photo of Ribblehead under construction at the following link, I think it shows a set of 6 arches on the left, going as far as a wider pier just as you describe?

Ribblehead Heritage Tours Restart

The iconic Ribblehead Viaduct and its associated shanty site is becoming a popular destination for visitors to the Yorkshire Dales, despite only being open for four days in August.

yorkshiretimes.co.uk

 

[Andy873]

Bit in bold - how do you believe the piers are reinforced?

No idea yet on that one I'm afraid.

There’s a good photo of Ribblehead under construction at the following link, I think it shows a set of 6 arches on the left, going as far as a wider pier just as you describe?

Yes, it looks that way and thanks for the link to the photo, very interesting!

With regard to the piers, the bases were wider than the top and I've reflected that in my new drawings (Attached).

One thing to bear in mind is that if the arch is constructed on one side of a pier and not the other, then there is an unbalanced lateral force that might topple the pier. So I imagine groups of arches would be constructed simultaneously.

That looks and sounds right to me.

The structure around the springing point is designed to have some protruding feature to support the wooden formwork.

Yes, that's correct too. Again, looking at photos of viaduct constructions each would to be arch (carrying a double standard track gauge) seems to have six protruding blocks at the top of each pier or if you like 6 on one side and 6 on the other. These were designed to hold up the six temporary wooden arches.

I've attached two more drawings, untitled 2 shows all the piers and embankments in place with some of the wooden arches complete. Photos suggest that all completed piers without the wooden arches were probably connected by horizontal beams. I've also drawn a close up elevated (top view) of one of the piers showing the protruding support blocks with six arches across.

Have a look on Flickr for Martholme Viaduct - at least one photo shows the support blocks still in place.

Untitled 3 shows some stone arches have had their bases constructed - looks like it's quite literally a balancing act. Here I've added in diagonal wooden beams for extra support as the stone arches take shape.

Looking at the photos once more, it seems that all sorts of wood beams were used. It really depended on the engineers judgement, terrain, weight and size of the arches etc.

I saw a TV program years ago where the presenter was trying to link the Egyptian pyramids with those in South America - it was pointed out to him that if you want to build upwards before the modern world what you would end up with is a pyramid - in other words, although different viaducts were built by different railway companies when it boils down to things there are some tried and tested constants...and only so many ways to build Victorian viaducts.

Attached are the two drawings. They are my best guess! Am I getting any closer?

 

[edwin_m]

No idea yet on that one I'm afraid.


Yes, it looks that way and thanks for the link to the photo, very interesting!

With regard to the piers, the bases were wider than the top and I've reflected that in my new drawings (Attached).


That looks and sounds right to me.


Yes, that's correct too. Again, looking at photos of viaduct constructions each would to be arch (carrying a double standard track gauge) seems to have six protruding blocks at the top of each pier or if you like 6 on one side and 6 on the other. These were designed to hold up the six temporary wooden arches.

I've attached two more drawings, untitled 2 shows all the piers and embankments in place with some of the wooden arches complete. Photos suggest that all completed piers without the wooden arches were probably connected by horizontal beams. I've also drawn a close up elevated (top view) of one of the piers showing the protruding support blocks with six arches across.

Have a look on Flickr for Martholme Viaduct - at least one photo shows the support blocks still in place.

Untitled 3 shows some stone arches have had their bases constructed - looks like it's quite literally a balancing act. Here I've added in diagonal wooden beams for extra support as the stone arches take shape.

Looking at the photos once more, it seems that all sorts of wood beams were used. It really depended on the engineers judgement, terrain, weight and size of the arches etc.

I saw a TV program years ago where the presenter was trying to link the Egyptian pyramids with those in South America - it was pointed out to him that if you want to build upwards before the modern world what you would end up with is a pyramid - in other words, although different viaducts were built by different railway companies when it boils down to things there are some tried and tested constants...and only so many ways to build Victorian viaducts.

Attached are the two drawings. They are my best guess! Am I getting any closer?

The diagonal wooden beams might be an alternative to having a wider pier so it doesn't need all constructing at once, but I don't know if this was the case or even if it was done at all.

Not sure about your statement in bold! The Romans certainly knew about arches and some of their aqueducts included just as many as any modern viaduct, though probably somewhat smaller. So the techniques must date back a couple of thousand years before the Victorians.

 

[Pigeon]

I've never seen any photos including anything like those inclined props, nor for that matter any kind of "reinforcement" designed to apply the same kind of lateral force.

The arch isn't an arch until you've finished it... Until you have a continuous half-ring of masonry from one pier to the other, it can't exert any lateral forces on the piers. While there's still a gap in it all it's trying to do is fall down in the middle, hence the formwork to support it. The formwork is not an arch; it's simply a beam, and transmits only vertical forces to its supports. Any lateral forces at that stage are contained within the formwork truss and not transmitted to the supports.

Furthermore, on a half-completed viaduct, such as the above photo of Ribblehead with part-completed arches between piers at one end only, and all those arches in roughly the same state of completion, the lateral thrust from any arch in the middle is counterbalanced by the equal and opposite lateral thrusts from the arches on either side of it. It's only the one at the end that exerts any unbalanced lateral force and relies temporarily on the lateral stability of the last pier, and the unbalanced force is only that due to that one arch, not the sum of all six (in that photo). This means that the wide pier does not need to be unreasonably wide to keep the thrust line within the middle third during this stage of construction.

The wide piers also serve the function of limiting the damage if the viaduct decides to fall down; if, say, one pier is built on a soggy bit and subsides, there is a decent chance that it will only collapse the arches between the wide piers on either side of it, and the arches on the other sides of the wide piers will stay up. So you only have to repair the gap in the middle of the viaduct instead of rebuilding the whole thing.

 

[stuving]

The lateral force may be smaller than its final value, but I don't think it will be zero. For one thing, as you start placing voussoirs on centring at the end, its slope is so steep they will slip down onto the springing. Then, as the arch builds up, the voussoirs need to be pushed close to each other for a snug fit. And when the keystone is inserted it will start to put the arch into compression and so load the piers laterally. As the spandrel and the rest of the bridge puts load on that arch, the centring - which is quite elastic - will deflect and take less of the weight. Is the centring even designed to bear the whole weight of the bridge over one arch?

 

[edwin_m]

The lateral force may be smaller than its final value, but I don't think it will be zero. For one thing, as you start placing voussoirs on centring at the end, its slope is so steep they will slip down onto the springing. Then, as the arch builds up, the voussoirs need to be pushed close to each other for a snug fit. And when the keystone is inserted it will start to put the arch into compression and so load the piers laterally. As the spandrel and the rest of the bridge puts load on that arch, the centring - which is quite elastic - will deflect and take less of the weight. Is the centring even designed to bear the whole weight of the bridge over one arch?

I agree these will happen, but are likely to be a lot less than the final lateral load when the arch is supporting everything above it rather than just itself. The centring only needs to support it until the voussoirs and keystone are in place, when the arch becomes self-supporting. In principle it can then be removed, although I wonder whether they might leave it in place for the first few courses above it "just in case".

 

[Andy873]

The arch isn't an arch until you've finished it... Until you have a continuous half-ring of masonry from one pier to the other, it can't exert any lateral forces on the piers. While there's still a gap in it all it's trying to do is fall down in the middle, hence the formwork to support it. The formwork is not an arch; it's simply a beam, and transmits only vertical forces to its supports. Any lateral forces at that stage are contained within the formwork truss and not transmitted to the supports.

Furthermore, on a half-completed viaduct, such as the above photo of Ribblehead with part-completed arches between piers at one end only, and all those arches in roughly the same state of completion, the lateral thrust from any arch in the middle is counterbalanced by the equal and opposite lateral thrusts from the arches on either side of it. It's only the one at the end that exerts any unbalanced lateral force and relies temporarily on the lateral stability of the last pier, and the unbalanced force is only that due to that one arch, not the sum of all six (in that photo). This means that the wide pier does not need to be unreasonably wide to keep the thrust line within the middle third during this stage of construction.

The wide piers also serve the function of limiting the damage if the viaduct decides to fall down; if, say, one pier is built on a soggy bit and subsides, there is a decent chance that it will only collapse the arches between the wide piers on either side of it, and the arches on the other sides of the wide piers will stay up. So you only have to repair the gap in the middle of the viaduct instead of rebuilding the whole thing.

Thanks, that's a very good explanation. I'm no engineer and never have been but it was the lateral forces that were troubling me.

The centring only needs to support it until the voussoirs and keystone are in place, when the arch becomes self-supporting. In principle it can then be removed, although I wonder whether they might leave it in place for the first few courses above it "just in case".

More good points from @Edwin and @stuving!

One question that's not been answered yet is was mortar used?

 

[Spartacus]

There's, perhaps unsurprisingly, quite a lot of photos of Victorian viaducts under construction, usually in books covering the history of lines. Often the photos are of when stone viaducts replaced wooden ones or when viaducts were replaced following the discovery of major faults or collapses, something that it seems was far more common than most people realise.