Durability.

[connect2]

All right so ok... if u can wander thorough Europe etc. and see buildings 400 + years old... ya ya ya i understand the concept of mass ... why then r our buildings after 20 some years requiring extensive repair? ... is this science at its best?

 

[HgTX]

What percentage of the buildings built 400 years ago are still standing? What percentage of the buildings built today might expect to last the same length of time with proper maintenance? You have to answer both of those questions before implying that things were built better 400 years ago.

That which survived all this time was way overdesigned. There wasn't a whole lot of analysis; the solution was to throw a whole lot of material at it. When you ruled the area, you could spend whatever you wanted on your building. Today we know just how little we can get away with, and walk that line. There's less room for error or deterioration.

But most importantly see my first paragraph.

Hg

Eng-Tips policies: faq731-376

 

[JAE]

yup - with no labor unions and with slave labor they could build them less expensive and heavy.

 

[Zambo]

connect 2,

you say that there are modern buildings which need extensive repair after 20 years. Well obviously something wrong there.....

 

[pba]

Some extra comments:

Most old European buildings were not built with slaves, but with skilled artisans.

It is wrong to simply assume that these buildings were 'way overdesigned'. Frequently this is not the case. Many old timber roofs are hard to justify under current codes. Buttressed walls and flying buttresses often do not stand under rigourous analysis but have remained intact for hunreds of years.

There is (probably) a wealth of building knowledge used in these great buildings which is now lost to us. Given that our construction works are very different, this is possibly no serious loss!

HOWEVER

Almost all significant old buildings have programmes of ongoing maintenance and repair way beyond what would be tolerated on a 'modern' building. Often this work has been constant since the completion. Over a period of time that worst problems of construction have now been resolved.

 

[archeng59]

one example of an old building with very high maintenance is the Leaning Tower of Pisa. While it is a wonderful architectural design, millions of dollars (perhaps billions) have been spent since it was constructed trying to shore up the foundation and strengthen the structure to keep the building from collapsing. It is my understanding that many of the old masonry cathedrals in Europe have tremendous amounts of maintenance year-round to keep them structurally sound. just because a building is hundreds of years old, doesn't mean it's a better design. new structural design methods and construction materials are likely being used to keep the building from falling down.

 

[pba]

Pisa!

Good one. Correct me if I'm wrong but I recall that Burland did some soil extraction works a few years ago and had stabilised the tower? You are right - Vast amounts of money has been spent on this tower. I'd say rightly so, as it is truly unique.

By the way, did you know that the original builders had to alter their verticality several times as the tower 'wobbled' as they built it?

 

[samdamon]

I would argue that the overall quality of the built environment in Europe is much higher than it was 400 years ago. The old european european cathedrals and institutional buildings that that survive to today are extremely special cases. They sometimes took more than a lifetime to complete. Their cost was no object. They were done using the best available materials available at the time, and using the highest and best structural design (such as it was)that was available at the time. However, I believe that the general populace that lived and worked around and worshipped in these beautiful cathedrals and buildings frequently lived in terrible conditions.

Today we rarely build anything intended to last for centuries, but the advances in applied physics, building materials etc have benefited almost everyone in the developed world in that the places we live, work and worship are generally far better designed and constructed than they used to be. I think that is true even considering just the last 100 years.

All my humble opinion.

Anyway, connct2, a few years ago I stood inside the Porta Nigra in Trier for a few minutes. It was erected before Christ, and was once part of a wall that protected the city. No doubt that Roman legions had tromped through its gates! Napoleonic-era sculptors had carved religious figures into the massive walls, and both ancient and modern soldiers had incised graffiti in odd places. It was black with the grime of centuries and constant use. They don't build 'em like that here in Jersey, ha ha!

 

[Tmoose]

I seem to remember a TV documentary about the cathedrals and their design(ers), and some of the first ones of each genre fell down.

 

[JStephen]

Some additional observations:
I seem to recall that some of the ancient greek structures survived for centuries and were then destroyed by earthquakes. Simply because a structure has been there for 400 years does not mean it is structurally sound now.

Secondly, we build to specific criteria. If low initial cost is the primary concern, that's what you get then, and that's what you got back then, and of course those structures are all gone now. If indefinite lifespan is the criteria, you get something different and pay accordingly. I'm not aware of any building techniques from the middle ages or from ancient times that are not available now- simply, no one wants to pay for those methods now. (The one exception might be the availability of very large timbers derived from old-growth trees).

Thirdly, the choice of durable materials is in some cases accidental. You read, for example, that King David's palace was built of cedar, and highly valued for that. Yet that almost guaranteed that it would not last like the pyramids (enemy actions notwithstanding).

My wife's uncle was once at the Taj Mahal. He told about seeing a worker replacing some tiles, and he brought back some of the old pieces. But even then, they weren't necessarily the original tiles- the whole thing may be been reworked several times through the years.

 

[archeng59]

pba, you are right about struggles with that building since day one practically. there was an article in one of the engineering magazines a few years ago that discussed the history of the building. I wonder how many lawyers would make a living on this building if it was constructed today? wow.

 

[JedClampett]

This all remind me of "Monty Python and the Holy Grail", and their construction techniques:
"When I first came here, this was all swamp. Everyone said I was daft to build a castle on a swamp, but I built in all the same, just to show them. It sank into the swamp. So I built a second one. That sank into the swamp. So I built a third. That burned down, fell over, then sank into the swamp. But the fourth one stayed up. And that's what you're going to get, Lad, the strongest castle in all of England."

 

[archeng59]

Monty Python and the Holy Grail... laughing just thinking about it.

 

[JStephen]

"The Great Arch Wells cathedral....The central cathedral tower, which rises to a height of 160 feet, was continued in 1318, having, in earlier years, only been carried up to the level of the roof. It is thought to have formed a dramatic lantern with triple lights to full height on each side. It was capped by a small spire. Some years afterwards, however, it was found that the four massive piers were sinking and were insufficient to carry the weight of the tower. A catastrophe was averted with remarkable skill by the medieval builders who placed inverted arches on three sides under the lantern. Thus supporting the piers from top to bottom. The whole work, which Glastonbury later copied, was accomplished with graceful effect. Externally, the central tower was rebuilt as we see it today after a serious fire in 1439. The south tower was not begun until after 1386. The north tower, begun in 1424, presents some slight differences of detail.

Edited from "Cathedrals" (1924)."

From another website, FYI.

 

[connect2]

All right so that went in a bit different direction than i thought it would (Clash of Civilizations hardly) ... maintence though came up several times which is good. Massive was meant in terms of stone and masonry vs. cold formed steel as an example wrt. design service life, durability, and reasonable expectations. And we might ask the same question wrt. creep, shrinkage, and deflection in reinforced concrete ... never minding relaxation in tendons of pre-stressed concrete ... chloride attack say what? Time dependant said whom? Time i guess is what we're talking about me thinks, 'blinded by science' seems to me there was a song wrt. ...