Medieval Structural Design 1

[Ussuri]

I have always been fascinated with old medieval structures, castles in particular, but also cathedrals, churches, abbeys etc but I have always wondered how they were designed.

Was it done by rule of thumb, if so do we still know these rules? Was it trial and error? If something fell down did they just start again? or did they actually do design calculations to substantiate things?

And another thing, I wonder if they did drawings or just arrived on site and thought 'OK, that stone there, that one over there'.

I find it amazing that we were able to build such enormous structures all those years ago.

Does anyone have any ideas? If there were designs/calculations/drawings made, and they still exist I would be really interested in seeing them?

 

[arto]

See if you can find "The Various and Ingenious Machines of Agostino Ramelli" by himself. Lots of cool woodcut pictures of Machine Design in the Renaissance.

 

[RDK]

The History and the Discovery channels often have shows on how these were built. They are written for the popular audience and so are light on the engineering aspects but there are some good shows on the construction of these places.



Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[Ashereng]

The Egyptians when they built their great pyramids did use some form of trial and error. First a small pyramid, then bigger. There is a "crooked" pyramid that had to be fixed by using two different slope gradients for the sides - one for the lower level and another for the upper portion that was starting to go wonky. Then, finally, the one at Giza. I've probably missed a few, but you get the idea.

I am sure that most European castles, churches and etc. probably used some sort of trial and error. Unfortunatedly, history usually preserve the stuff that works. All the errors are usually lost (demolished by the original builder/owner since it didn't work, or nature took it down since it didn't work).


Now, the questions of drawings is interesting. We produce massive amounts of drawings in my industry for things that are much small in scope than a castle or church. I wonder what type of document control they had back then?

 

[TheTick]

Not long ago, being a successful military officer entailed being an adept civil engineer, i.e. George Washington. Winning battles was only half the battle. Troops had to get there, be fed, housed, etc.

Much Masonic lore is rooted in the carefully guarded knowledge of building craftsmen. This goes back hundreds (thousands?) of years.

 

[Timelord]

Ussuri,

You might want to explore the history of the Beauvais Cathedral in France. There was a great discovery channel (or was it NOVA) show about the engineering that went into it. It is infamous for collapsing, more than once, and being rebuilt with lessons learned. I believe the story goes that the Bishop in Beauvais got in a disagreement with the french crown and the cathedral was ment to be grander than the Notre-Dame cathedral in Paris, kinda a one-ups-manship to spite the crown.

Timelord

 

[zeitghost]

Spires used to fall down quite regularly and get rebuilt.

A lot of cathedrals in the UK have very dodgy foundations... almost to the extent of having next to none.

I seem to recall that Salisbury cathedral is built on gravel with little in the way of foundations and the ground water level is a matter of inches below the floor.

 

[zeusfaber]

Salisbury does have the structural advantage that the medieval builders never quite had the courage to remove the wooden scaffolding from inside the spire after they'd finished. It's still in there now.

A.

 

[DaveVikingPE]

There's some interesting castle engineering websites out there, that I know.

The Vikings were pretty good at naval architecture, fer sure, man.

 

[GregLocock]

One of the best lectures we had at uni was on the architectural design of gothic cathedrals.

One trick they probably used was to build an upside down model of the crosssection of the nave and its supports in string, and then added weights to represent the roof and so on.

By adjusting the angles and the weights (those pointy spires on top of arches and pillars aren't there just for looks) they could get the whole thing square. The line of each string then showed the thrust line through that member, and had to be kept to the middle third of the column.

I am told Gaudi used the same method, but in 3d.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Ussuri]

the medieval builders never quite had the courage to remove the wooden scaffolding from inside the spire after they'd finished

Cool, I wonder if it is still classed as temporary works then?

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Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
Archimedes

 

[EnglishMuffin]

Although this is slightly off the subject, I do know that they used drawings (of a sort) in classical times. This is known because somewhere in the eastern mediterranean there is a half completed Greek temple which somehow got preserved (I think it was buried in sand or something). In the inner part of these classical temples, there were vertical walls. One of these was left undressed, and line drawings of all the details were chiselled onto it. It would take many years to complete these temples, so this was a good way for different groups of workers to keep track of the correct dimensions over time. One of the particularly neat things was that the outer columns were all drawn in shortened form, so that they would fit on the "drawing" surface. Since the columns were actually slightly barrel shaped, this allowed drawing the sides of the shortened columns with what was actually quite a small radius, while the column width was shown full size. This enabled workers to scale off the drawing to get the correct dimensions for the full size columns. If the temple had been completed, the "drawing" surface would have been finish dressed, thus erasing all evidence of how it was done. Full size layout drawings chiselled into the ground have also been uncovered in Rome - in particular for the Pantheon. It is not inconceivable that similar methods were passed on down to the medievel builders. I also think there is some evidence that they used scale models.

 

[pba]

I could be wrong, but I thought the timberwork within the spire of Salisbury Cathedral couldn't be removed as you can't get up there because of all the timber work...

 

[zeusfaber]

I've certainly been up there in among some of it.

Whether you could get to all of it, dismantle it without having to cut beams in-situ, or get any of it out without turning it to matchwood first could well be another matter.

Although 800 years old, Salisbury has a supremely efficient acoustical design - it is one of the easiest and most pleasing buildings to sing in I've ever come across. Does anyone know whether that was just down to long experience, or might there have been some clever modelling tricks there too?

A.

 

[waross]

Further to the comment that "nature took it down since it didn't work".
I have heard the buildings in Antigua, Guatemala described as being of the "Darwinian school of architecture".
The town is prone to earthquakes and only the fit survive.

 

[ScottyUK]

zeusfaber,

It achieves it's acoustic performance rather more elegantly than the silver slug on Gateshead's quayside, which also claims to have excellent acoustics.

http://www.freefoto.com/preview.jsp?id=1044-02-6&k=The+Sage+Gateshead

Wonder if it will still be standing in 800 years? One would rather hope not!


----------------------------------

I don't suffer from insanity. I enjoy it...

 

[zeusfaber]

That's truly ghastly. Where's the salt?

A.

 

[Ussuri]

I just came across this while rummaging around the net. It seems these folks have designed and built their own castle, replete with all the modcons you would expect in the 21st century. I do wonder whether its a bit of a contradiction though?

http://www.oldcastleshop.com/index.html

http://www.oldcastleshop.com/blick-burgtor.htm

 

[dik]

Try digging up some videos or texts by David McCauley... I've seen articles by him on Castles, Pyramids and Cathedrals... they're excellent

Dik

 

[jmw]

Salisbury is also famous for having as its foundations a raft of logs sunk into the water loogged ground.
Hard to be critical when it worked until big cracks started to appear in the 20th Century and a diver spent some years replacing it all section by section with concrete.

(By the way, I like the Sage a lot more than I like the tower block behind it, though I am not agreat fan of Sir Norman Foster's other "Gherkin", Reichstag dome etc.)

The keeping of secrets, a masonic code etc. is possibly the cause of more lost skills than anything else. The Romans knew how to use concrete and cement yet this was lost for centuries after the collapse of the empire.

However, lime mortar, which served in its place, has its advantages... since the core of a castles walls would be rubble and lime mortar, the lime mortar had an important advantage over the Roman materials... it acted like a jelly when struck by a stone from a catapult.
Also, and you can see this in old buildings where the foundations have sagged or the building settled, the fact that lime mortar never actually sets means that it yields and adapts where modern cements would crack and the structure fail.

Stone is/was difficult to work with the available tools yet some stone is easier to work when fresh from the quarry and still "green" i.e. with the quarry sap still in it... i.e. moisture. Once cut and errected the moisture would escape through the open air surface and the minerals dissolved in it would be carried to the surface and form a crust as the moisture evaporated. A good natural protection until the advent of modern air borne pollutants.
Its perhaps why the Towere Of London was built (faced) with Reigate sandstone which is now in trouble.

Builders could and would work to the limits of their capabilities, the available technology and the available materials.
Some cathedrals took so long to build that the advances in knowledge are evident in their structure; the transition from the norman arch and huge columns at lower levels, to the gothic pointed arch and light delicate columns and, my favourite, the flying butress... all of which indicates increasing knowledge and confidence and the greater understanding of engineering involved.

Had these buildings been built with todays philosophies, financing and fear of failures, I wonder just what sort of structures we would have inherited.

Perhaps more importantly, one wonders how much our approach today, in some fields, might not be limiting our achievments?
Today conservatism rules almost every approach, that and a focus on the bottom line.
Back then they were not driven by the same commercial objectives or financial constraints.
One wonders if they were not far more adventurous than we are today.

JMW

http://www.ViscoAnalyser.com