[Peter Dow (OP)]

What started off as my politically-motivated blog post last week, I've since been elaborating on, in an engineering design style, so I thought I should get some professional help. 


BBC: “Falling ice causes first Queensferry Crossing closure”

Keeping such bridges open even in icing conditions is really not rocket science. What, to me anyway, is the obvious solution – to pass an electrical heating current through the bridge’s support cables –  doesn’t seem to be “obvious” to other research scientists and engineers whose “Thermal Systems” for melting the ice are reviewed here.

I suggested this simple solution, outlined the calculations required and warned of some dangers in an email to the Queensferry Crossing bridge authorities and contractors in March 2019, but as usual, the authorities ignore solutions until there is a political price to be paid for continuing to ignore solutions in a pig-headed, in-denial kind of way that politicians like to get away with, if they possibly can.

There follows a link to a PDF of the email I sent the bridge authorities last year – hopefully you can click the link and open and / or download the PDF so you can read it.

Queensferry falling ice hazard solution – electrically-heated cable stays

Deicing power for 70km of cables
@ 100W/m = 7MW = household electricity within a 3 mile radius of the bridge.
@ 250W/m = 17.5MW = household electricity within a 5 mile radius of the bridge.

Cable strands


Some strands in the cable are better situated for heating the cable than other strands, depending on their position in the cable as I have labelled them alphabetically, beginning with the label “A” for the centre strand (which is the worst strand for heating the outside of the cable, where the ice would be) and labelling the outer strands last in alphabetical order, which are best for heating the outside of the cable.

The cable strands are by convention named here using the format – “(Number of strands in the cable)-(Letter)”. Thus the centre strand in the 55-strand cable is named as “55-A”, the 6 strands immediately surrounding the sole 55-A are all named of type “55-B”.

For each strand in the cable we can assign a factor of heating capacity.



For the 55-strand cable, total heating capacity factor assigned is 48.

For the 55-strand cable, there are a total of 24 strands which have utility for heating the cable – 6 of the 55-F type name strands, 6 x 55-Gs and 12 x 55-Hs. The 31 other strands (the 55-A to 55-Es) are not needed for heating per se, though could carry electrical currents whether by design or otherwise.

We can tabulate for each strand label, the heating power fraction and percentage, according to each strand’s heating capacity factor as a fraction of the cable’s total heating capacity factor.




For the 61-strand cable, the total heating capacity factor assigned is 54.

For the 61-strand cable, there are a total of 24 strands which have utility for heating the cable – 6 x 61-Gs, 12 x 61-Hs and 6 x 61-Is. There are 37 other strands – the 61-A to 61-Fs.




For the 73-strand cable, the total heating capacity factor assigned is 54.

For the 73-strand cable, there are a total of 30 strands which have utility for heating the cable – 12 x 73-Hs, 6 x 73-Is and 12 x 73-Js. There are 43 other strands – the 73-A to 73-Gs.



See my blog post for details for 85-, 91- and 109- strand cables.


VSL SSI 2000 Stay Cable System
There are a number of options available in the VSL SSI 2000 Stay Cable System so these figures cannot be confirmed without sight of the Queensferry Crossing engineering design specifications (or by actually measuring the cables, which I am unable to do!).



For now, I am assuming for simplicity that the required maximum heating power in watts/metre is the same as the stay pipe diameter in mm. This is not far off the maximum heat radiation from the sun on such a stay pipe, square on to the sun, at midday, midsummer, on a cloudless day – or more than enough heat to melt any ice in short order!

At this maximum heating power and after the cable cores warm up, they will emit 1000÷π = 318 Watts of heat energy per metre-squared of stay pipe surface area.



It is now possible to tabulate for each cable-label strand, the maximum heating power per metre and assuming a strand resistance of 0.001137 ohms per metre, what the maximum strand current would be.



Cable voltages and power
To calculate the cable voltages and power and to calculate the total maximum power to heat all the cables of the Queensferry Crossing accurately, I will need to know how many of each size of cable and their lengths.

Direct Current Heating
Those theoretical differences between strand situations only matter for direct current heating if it is possible electrically to isolate strands from each other. The strands are attached via steel wedges to a steel anchor head, which, for now,incidentally connects all the strands together electrically.

Please note, however, that when introducing a design requirement to conduct large electrical currents between strand pairs at the tower anchor heads (see DC Circuit Diagrams) the incidental electrical connection at the wedges may be of insufficiently or unreliably low resistance and should be supplemented with an ultra-low resistance connector between the strand ends, to avoid faults developing from excessive resistance heating at the wedges.


Cable anchorages


Teflon/PTFE-coated glass fibre fabric sheaths to electrically isolate the strands from the anchor head. The outer strands are for heating. The inner strands are for signals.

It should be possible to insert Teflon/PTFE-coated glass fibre fabric sheaths between the wedges which grip the  strands we wish to insulate and to isolate from the anchor head and from each other, unless and until they are connected to electrical heating or signal circuits.

The signal circuits could be used to report to the power supply control electronics at one end of the cable, the output of heating current sensors at the other end of the cable, to help to detect current leakage faults in the cable strands’ insulation, to implement a residual current device, to trigger safety power-cut-outs or circuit-breakers, most notably.

Teflon is a good insulator and is used for thread seal tape illustrating the properties of lubrication of the wedge to its housing cone required. The glass fibre fabric should provide strength under compression and a superior dimensional stability versus creep under load that a pure Teflon sheath may suffer from.

Clearly the sheath would have to remain thick enough to insulate against the highest voltage difference which might appear between the heating strands and the anchor head.

UPDATE 22/02/20

Such sheaths would likely not be available as an off-the-shelf product in the required dimensions, though general purpose PTFE-coated fibre glass cloth is commonly available and this expandable E-glass sleeving, expands from a relaxed internal bore of 15mm to a maximum bore of 38mm and insulates to 500V when not expanded, which is a useful size while relaxed to accommodate the strand and while expanded to accommodate the wedges.

The insulation should cope with the highest DC voltage of about 100 Volts, used to power the longest and highest heating capacity factor strands, albeit that this sleeving is inappropriately resin-coated and would therefore likely require to be custom adapted, the resin cleaned off and re-coated with PTFE, tested and proved in the laboratory. Perhaps wrapping the wedges in PTFE thread seal tape is all that is required to supplement the product as supplied for satisfactory performance? A promising avenue for research.



DC Power Supplies
Not forgetting DC power supplies and I have noticed a comprehensive range of 3kW to 10kW DC power supplies here that I think will do nicely, an average of about a dozen power supplies per cable (more for the longer cables, fewer for the shorter cables), about 3500 power supplies required to de-ice all 288 cables.



Where to store the cable power supplies?
Let’s examine the option of storing the cable heating power supplies in the towers, racked next to the anchorages of the cables which they will be heating. There might just be enough room to squeeze in another half a tonne of power supplies for the 4 cables per floor (assuming their racks are securely attached to the tower walls), 12 tonnes worth of power supplies for all 24 floors per tower, for all 3 towers!

Even at 94% efficiency for switch mode power supplies, each tower’s cable power supplies could be generating at most about 0.4 MW of waste heat energy. A new massive extractor fan fitted into the roofs of the towers would be required to cool the inside of the towers while the DC power supplies are heating the cables.

Considering how cramped the insides of the towers are already, the daunting cooling problem, not to mention the risk of a tower fire destroying all of a tower’s power supplies at one time, it looks to be much the better option to install the cable power supplies on the deck, next to the deck anchorages to allow them to be supplied with power.



The stay cables penetrate the surface of the deck, as can be clearly seen in this next photograph, taken during construction.



Therefore best access to the anchor heads, to attach the cable heating power supplies, may be from inside the deck, where the power supplies themselves should be stored too.

5/3/20

Update 25/2/2020

DC Circuit Diagrams
Locating all the electrics at the deck anchorages, while leaving the strands earthed at the tower anchorages, offers advantages for design, development, installation, commissioning and servicing.


Circuit Diagram – 2 heating strands, 1 power supply


Heating strands pair current balance detector

The window detector circuit compares the isolated power supply’s potential with respect to earth to detect the expected balance of current and voltage in the heating strands pair. If an imbalance fault develops then the safety switch is used to cut the power.

DC Summary

So isolating the strands for DC heating purposes presents technical challenges. It would be very convenient if the outer strands could be preferentially used for heating purposes without having to isolate the strands electrically etc. but to achieve that we must consider using not direct current but alternating current instead.

Alternating Current Heating
The skin effect observed with alternating current changes matters in that with increasing frequency the heating current will tend to distribute towards strands nearer the surface of a cable. However if too great a frequency is used then the skin effect will increase the resistance of even the most superficial strands so much that inappropriately high and difficult to insulate against voltages would be required to obtain the required heating power.

Assuming that the appropriate AC frequency can be determined for preferentially heating the superficial strands of the Queensferry Crossing stay cables, although there would be no need to isolate the strands from the anchor head, there then presents the challenge of isolating the anchor heads and anchorages so that the current is not dissipated through the bridge instead of heating the cables as required.

Having isolated the cables for heating purposes, one may then wish later to reconnect the cables electrically to the rest of the bridge and disconnect the heating power supplies for lightning protection purposes. Certainly, one would not wish to encourage a lightning strike to find its way to ground via the bridge’s cable deicing power supplies!

Tower ice
To prevent the bridge piers or towers (with non-conducting concrete surfaces) from icing up, they could be surface fitted with new electrical heating trace cables which are then appropriately electrically-powered for deicing when necessary.

Ideally, such additional heating elements would have been embedded into the surface of the piers at construction time. Too late for that now.

Another option to consider is heating the hollow piers from within. However, considering the considerable mass and thickness of the piers their surfaces would have to be kept above freezing temperature all winter long. Heating the piers from within, there simply wouldn’t be time to allow the piers to get freezing cold because there was no icing then suddenly heat them from the inside to deice a sudden incidence of icing.

So heating from within bridge piers would use more electricity, though the cost shouldn’t be prohibitive – surplus grid electricity is a common occurrence at times of high wind power generation, so the electricity grid managers should offer a very low price for such electricity (just the grid connection charge) – plus it should be a lot safer upgrade from the point of view of bridge users – far less chance of things falling onto the road during the fitting of the piers’ internal heating elements.

Heating the towers may be as simple as a big electric heater on the ground floor, the warm air rising up the insides of towers in between the open stairways and scaffolding.

[Bored chemist]

The heat of fusion of ice is 333.55 J/g.
100 Watts would melt about 1/3 grams of ice per second.
A metre of cable 100 mm in diameter has an area - as you calculate- of roughly a third of a square meter

I am assuming for simplicity that the required maximum heating power in watts/metre is the same as the stay pipe diameter in mm. 

So, if snow is falling at an equivalent of more than 1/3 grams per sec on 1/3 m^2 i.e. 1 gram per m2 per sec, you aren't going to melt it.
Assuming that the met office rainfall map is sensible
https://www.metoffice.gov.uk/public/weather/observation/rainfall-radar#?map=Rainfall&fcTime=1582010400&zoom=5&lon=-4.00&lat=55.01

we can expect precipitations up to 32 mm/hr
32mm of rain on 1 m^2 is 3.2*100*100 grams per hour
That's 32 kg/hr
which is about 9 g/m^2/sec

So you need 10 times more power just to melt the ice that lands on it. (Please don't waste time telling me the wires are vertical)

You need even more if it's going to have to heat it in air that's above freezing.

I'm also intrigued by the notion that it matters much which wires you heat.
Metals conduct heat quite well.
If you heat the ones in the middle, the heat will diffuse to the outside.
If you heat the ones round the perimeter, the heat will diffuse into the core of the cable.
Fundamentally, the only place that (most of) the cable can lose heat is from the surface, so it hardly matters which bits you heat.

Also, have fun with galvanic corrosion.

Certainly, one would not wish to encourage a lightning strike to find its way to ground via the bridge’s cable deicing power supplies!

Lightning goes exactly where it damned well pleases.

the maximum heat radiation from the sun on such a stay pipe, square on to the sun, at midday, midsummer, on a cloudless day – or more than enough heat to melt any ice in short order!

Snow is noted for not melting very quickly when the sun shines on it and, to be useful, your scheme has to melt it in real time.

[Peter Dow (OP)]

The heat of fusion of ice is 333.55 J/g.
100 Watts would melt about 1/3 grams of ice per second.

If the ice was at freezing temperature and didn't have to be warmed up from below freezing - 100/333 = 0.3 grams of ice per second.

A metre of cable 100 mm in diameter has an area - as you calculate- of roughly a third of a square meter

I am assuming for simplicity that the required maximum heating power in watts/metre is the same as the stay pipe diameter in mm. 

So the surface area of a pipe per metre of length of pipe of diameter 100mm is 0.314 m² but don't take my word for it - here is an on-line calculator.
https://vodoprovod.blogspot.com/p/area-pipe.html

So, if snow is falling at an equivalent of more than 1/3 grams per sec on 1/3 m^2 i.e. 1 gram per m2 per sec, you aren't going to melt it.

Well snow wouldn't fall on the underside of the pipe but if that much snow fell on the pipe then not all of it could be melted, no, but no worries, because we don't have to melt all the snow that falls onto the pipe, just enough of the bottom layer of snow or ice so that the rest slides off.

https://www.avalanche.ca/tutorial/avalanche-terrain/slope-angle

Assuming that the met office rainfall map is sensible
https://www.metoffice.gov.uk/public/weather/observation/rainfall-radar#?map=Rainfall&fcTime=1582010400&zoom=5&lon=-4.00&lat=55.01

we can expect precipitations up to 32 mm/hr
32mm of rain on 1 m^2 is 3.2*100*100 grams per hour
That's 32 kg/hr
which is about 9 g/m^2/sec

So you need 10 times more power just to melt the ice that lands on it.

No, because you don't need to melt rain and hail will bounce off and snow will slide off.
All you need to do is to keep the pipe surface at or above freezing temperature - keep the pipe surface wet, not frozen, and gravity will do the rest.

(Please don't waste time telling me the wires are vertical)

I won't but it is worth mentioning that the shallowest slope of pipe is 19 degrees.

You need even more if it's going to have to heat it in air that's above freezing.

You mean air that's below freezing? More, admittedly, but not too much more.

I'm also intrigued by the notion that it matters much which wires you heat.
Metals conduct heat quite well.
If you heat the ones in the middle, the heat will diffuse to the outside.
If you heat the ones round the perimeter, the heat will diffuse into the core of the cable.
Fundamentally, the only place that (most of) the cable can lose heat is from the surface, so it hardly matters which bits you heat.

The metal conductors are insulated so there's nothing to be gained by heating the inner strands, and much to lose if you melt the insulation.

Also, have fun with galvanic corrosion.

The current in the strands won't effect corrosion, which is limited by the flow of oxygen and water to the conductor surface, not electrons.

Certainly, one would not wish to encourage a lightning strike to find its way to ground via the bridge’s cable deicing power supplies!

Lightning goes exactly where it damned well pleases.

Lightning rods have something to say about that. However, if the lightning strikes a cable then best that one at least of the strands offers a conducting path to ground and that none offer a path to a power supply.

the maximum heat radiation from the sun on such a stay pipe, square on to the sun, at midday, midsummer, on a cloudless day – or more than enough heat to melt any ice in short order!

Snow is noted for not melting very quickly when the sun shines on it and, to be useful, your scheme has to melt it in real time.

The pipe will melt the ice and snow and heat the water in contact with the pipe surface by efficient conduction, not by snow's inefficient solar radiation absorption.

[Bored chemist]

The current in the strands won't effect corrosion, which is limited by the flow of oxygen

No, water is sufficient.

[Petrochemicals]

Surface coat the cables and uprights in something that ice does not cling. Surely teflon would have an effect. Create all surfaces with a friction factor low enough to shed ice

[syhprum]

How about building tunnels instead of bridges as has been suggested for the Bering straight crossing .

[Peter Dow (OP)]

Surface coat the cables and uprights in something that ice does not cling. Surely teflon would have an effect.

If anti-icing chemical was painted or sprayed on would some of it drip or be sprayed onto the road, making for slippery, treacherous driving conditions?

If it was stuck on with sticky tape, would the sticky tape stay on, or come off?

Wouldn't the coating need re-doing every winter, or more often? Presumably the coating would suffer weathering? How long would it be good for?

They seem to use both de-icing and anti-icing chemicals for aircraft, though Wikipedia doesn't mention "Teflon" or "PTFE".

https://en.wikipedia.org/wiki/De-icing

Create all surfaces with a friction factor low enough to shed ice

That's what heating the cable will do.

[Bored chemist]

If anti-icing chemical was painted or sprayed on would some of it drip or be sprayed onto the road, making for slippery, treacherous driving conditions?

If it was stuck on with sticky tape, would the sticky tape stay on, or come off?

Wouldn't the coating need re-doing every winter, or more often? Presumably the coating would suffer weathering? How long would it be good for?

https://en.wikipedia.org/wiki/Millennium_Dome

[Peter Dow (OP)]

If anti-icing chemical was painted or sprayed on would some of it drip or be sprayed onto the road, making for slippery, treacherous driving conditions?

If it was stuck on with sticky tape, would the sticky tape stay on, or come off?

Wouldn't the coating need re-doing every winter, or more often? Presumably the coating would suffer weathering? How long would it be good for?

https://en.wikipedia.org/wiki/Millennium_Dome

The canopy is made of PTFE-coated glass fibre fabric,

insert Teflon/PTFE-coated glass fibre fabric sheaths between the wedges which grip the  strands

Snap.

It's one thing to coat a surface of glass fibre (melting point 1400 - 1600 °C) with PTFE on a production line in a factory and quite another on the surface of a HDPE (melting point 120 - 180 °C) stay pipe covering a bridge cable while in use.

Then again there is the option of wrapping the existing stay pipes with PTFE-coated fibre glass cloth. That's more of an option to consider.

[Bored chemist]

Is the Millennium Dome an example of a heated surface which melts ice?

No.

I think it is too late to try the PTFE coating option...

Google finds 21 million hits for  "ptfe spray".
I'm not saying this is a good idea, I'm just saying it's less impractical than wiring the bridge to the grid.

[Peter Dow (OP)]

I think it is too late to try the PTFE coating option...

Google finds 21 million hits for  "ptfe spray".

Without the quotes. With the quotes it is only 153,000 hits.

I'm not saying this is a good idea, I'm just saying it's less impractical than wiring the bridge to the grid.

Well why don't they cover aircraft with PTFE and why doesn't that work to solve all aircraft's deicing problems?

Covering the pipes with PTFE-coated glass fibre fabric might help but I would simply point out that everyone's house is connected to the grid but few roofs are covered with PTFE. There must be a practical reason for that, other than to stop the roof repair man from sliding off! 

[Bored chemist]

Without the quotes. With the quotes it is only 153,000 hits.

Do you not feel that 153000 is enough to choose from?
Well,  you can add a few more hundred thousand by using teflon instead of ptfe and changing the word order.

The fact is, of course, it just needs 1

There must be a practical reason for that,

There are obvious reasons.
Nobody cares much if there's snow on the roof.
People can't run  their computer using a PTFE roof.

Well why don't they cover aircraft with PTFE and why doesn't that work to solve all aircraft's deicing problems?

There are a few ways I know of that they use for deicing planes.
Inflatable rubber bits, trace heating and antifreeze sprays.

So far as I know, nobody does it by rebuilding the wing with weak points made of PTFE so that they can electrically isolate the leading edges and pass huge electrical currents through them.

So, given that doing so isn't practical for planes- because there are better ways to do it- perhaps that why the people you set your ideas to thought there were better ways to do it for a bridge.

[Peter Dow (OP)]

Without the quotes. With the quotes it is only 153,000 hits.

Do you not feel that 153000 is enough to choose from?
Well,  you can add a few more hundred thousand by using teflon instead of ptfe and changing the word order.

The fact is, of course, it just needs 1

Spraying PTFE all over the bridge is a non-starter.
A factory-produced cover for the pipes which comes with PTFE already securely attached in the factory is a possibility but access for the workers to attach the covers will be very difficult.

Well why don't they cover aircraft with PTFE and why doesn't that work to solve all aircraft's deicing problems?

There are a few ways I know of that they use for deicing planes.
Inflatable rubber bits, trace heating and antifreeze sprays.

So far as I know, nobody does it by rebuilding the wing with weak points made of PTFE so that they can electrically isolate the leading edges and pass huge electrical currents through them.

So you and I know that covering the ice-accumulating surface of planes with PTFE doesn't work.

The PTFE sheaths to isolate the strands don't add a weak-point but we'll be sure to test your "weak-point" theory in the laboratory, making such adaptations as are necessary to prove that strength is maintained.

So, given that doing so isn't practical for planes- because there are better ways to do it- perhaps that why the people you set your ideas to thought there were better ways to do it for a bridge.

They don't have a better way and they know it.

[Petrochemicals]

Surface coat the cables and uprights in something that ice does not cling. Surely teflon would have an effect.

If anti-icing chemical was painted or sprayed on would some of it drip or be sprayed onto the road, making for slippery, treacherous driving conditions?

If it was stuck on with sticky tape, would the sticky tape stay on, or come off?

Wouldn't the coating need re-doing every winter, or more often? Presumably the coating would suffer weathering? How long would it be good for?

They seem to use both de-icing and anti-icing chemicals for aircraft, though Wikipedia doesn't mention "Teflon" or "PTFE".

https://en.wikipedia.org/wiki/De-icing

Create all surfaces with a friction factor low enough to shed ice

That's what heating the cable will do.

To put it simply engineering is about finding a way. Infact its most tardy of them (engineers) they have not incorporated this into bridges for at least 100 years. Surface finish shapes eg dimples like a  golf ball or the reverse,  mini pyramids, paint etc. As you have demonstrated an electrical system of heating is unfeasably complicated and therefore expensive to be retrofitable and therefore maintainable. Its possible to go to the moon, yet beyond apollo we have not bothered for 50 years, until now for some reason, everything is a balance between cost and worth.

https://www.technologyreview.com/s/408558/mining-the-moon/

https://philosophia.uncg.edu/phi361-matteson/module-1-why-does-business-need-ethics/case-the-ford-pinto/

They could build extremley safe cars for both passengers and pedestrians, problem is no one would buy them and they would be expensive.

[Peter Dow (OP)]

As you have demonstrated an electrical system of heating is unfeasably complicated and therefore expensive to be retrofitable and therefore maintainable.

Actually, I've demonstrated that an electrical system of heating is feasible and what for others was too complicated to design in more like 200 years since the first wire cable bridges https://en.wikipedia.org/wiki/Suspension_bridge#Wire-cable is for me something I can do in a week.

Engineering designs are de rigueur full of lists of numbers in mind-numbing detail. It's what makes a good design foolproof not "complicated".

A terrible design plan that was no plan at all would leave lots of decisions to the construction workers to choose an arbitrary length, a thickness, a material, a strand, a voltage or a current and that would be a recipe for disaster because without the detail they don't know what to do, even where to begin.

Architects can't simply pass an artists impression to labourers and invite them to have a go.

[vhfpmr]

The glass fibre fabric should provide strength under compression and a superior dimensional stability versus creep under load that a pure Teflon sheath may suffer from.

Good luck with that one, the compressive strength of something like Duroid is about a tenth that of typical steels.

[vhfpmr]

So you need 10 times more power just to melt the ice that lands on it.

And then by the time you've got ~1kW/m^2, you'll have a temperature rise of something like 100-150K when the cable's dry.

[Peter Dow (OP)]

Duroid

I'm not familiar with Duroid, so I searched for it

Rogers RT/duroid® high frequency circuit materials are filled PTFE (random glass or ceramic) composite laminates for use in high reliability, aerospace and defense applications.
https://www.rogerscorp.com/advanced-connectivity-solutions/rt-duroid-laminates

When they say "random" what does that mean? If it doesn't mean "glass fibre fabric" but short isolated glass or ceramic fibres or particles or something then that's a different material with different flow behaviour under compression altogether than a cloth woven from long fibres.

[Peter Dow (OP)]

So you need 10 times more power just to melt the ice that lands on it.

And then by the time you've got ~1kW/m^2, you'll have a temperature rise of something like 100-150K when the cable's dry.

I specified

318 Watts of heat energy per metre-squared of stay pipe surface area

and I refuted the suggestion that more power was needed because there is no need to melt all the ice, but only the surface layer, so that the rest of the ice slides off.

So 0.318 kW/m² is the maximum power I have suggested.

[Bored chemist]

Spraying PTFE all over the bridge is a non-starter.

They paint bridges...

The PTFE sheaths to isolate the strands don't add a weak-point but we'll be sure to test your "weak-point" theory in the laboratory, making such adaptations as are necessary to prove that strength is maintained.

In the very real sense that PTFE isn't weaker than steel.

So you and I know that covering the ice-accumulating surface of planes with PTFE doesn't work.

I  have never tried it, have you?
I'm guessing that neither of us has, so your claim that "you and I know that..." is not true.
Why say it?

Actually, I've demonstrated that an electrical system of heating is feasible and what for others was too complicated to design in more like 200 years since the first wire cable bridges https://en.wikipedia.org/wiki/Suspension_bridge#Wire-cable is for me something I can do in a week.

So, what you are saying is that 200 years of experience says we don't need it.

Time to close the thread then