Twenty years ago when I worked for Siemens' U.S. research lab, a group of us went to Germany to collaborate with engineers in Erlangen and Berlin. We took some time out to visit East Berlin by bus through a checkpoint at the Brandenburg Gate. The Wall was still standing, but people were hacking away at it. Our hosts at Siemens gave us each a heavy hammer and a cold chisel so we could collect pieces of it as souvenirs. As I hacked away on the no-man's-land side of the wall -- there was a large gap that made it easy to get there -- a pair of goose-stepping East German guards marched by, studiously ignoring the activity. I stood transfixed, too stupefied to grab my camera. I brought home several pieces of the wall and gave some away. I have two left. The concrete is some of the hardest I have dealt with, harder by far than a typical sidewalk. The rebar (reinforcement bars) is interesting. European practice uses round bar, while American rebar is deformed to add ridges that increase bond strength. The rebar in the Berlin was deformed. Was it imported from the West? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Far off topic: Berlin wall
Started by ●November 8, 2009
Reply by ●November 9, 20092009-11-09
On 9 Nov, 04:29, Jerry Avins <j...@ieee.org> wrote:> The concrete is some of the hardest I have dealt with, harder by far > than a typical sidewalk. The rebar (reinforcement bars) is interesting. > European practice uses round bar, while American rebar is deformed to > add ridges that increase bond strength. The rebar in the Berlin was > deformed. Was it imported from the West?Don't know its origins, but the rebar I have seen has ridges or grooves (see a picture here): http://fil.nrk.no/torget/wp-content/uploads/nrk_media/auto_5913/full.jpg Maybe the eastern European stuff didn't need bond aids: It was usal for the old communist states to make perfect products. Their factories - being communist and thus perfect - did not pollute, so they did not need waste product cleaning facilities and so on. A rebar that had the bound aids was, per definition, not perfect so communist states would not have made them. A bit convoluted, but I am sure you get the idea. Rune
Reply by ●November 9, 20092009-11-09
Jerry Avins <jya@ieee.org> writes:> ... > The concrete is some of the hardest I have dealt with, harder by far > than a typical sidewalk. The rebar (reinforcement bars) is > interesting. European practice uses round bar, while American rebar is > deformed to add ridges that increase bond strength. The rebar in the > Berlin was deformed. Was it imported from the West?I doubt the DDR imported iron from the BRD or another western country. I am not sure what you precisely mean by ``round bar -- deformed bar'' --- no native english speaker --- but I suppose the bars you saw where nothing special in Germany. http://de.wikipedia.org/wiki/Bewehrungsstahl shows in the first picture the usual type as used in Germany today; until some years ago it was twisted in addition (Speaking of the BRD). (You may find some interesting notes on the history of such steel at the end of the Wikipedia article.) Here is my anecdote on reinforcement bars: a little more than twenty years ago I was visited by a cousin who was a construction engineer in the US. That was his second visit to Europe; first time was under the command of General Patton, second time he was engaged in the construction of a central repair facility for howitzers of the US Army. He saw some rebars lying around in my shed and found it very interesting that we have them with ridges even at a diameter of 6mm. I have some relations to concrete construction and never saw anything but material as shown in the picture used in newer work. Though I saw smooth round rods in some old (at least pre-WWII) fence poles. I skipped through http://en.wikipedia.org/wiki/Rebar and from this I guess that the German material is quite different from what is common in the US. As you have shown as an experienced metalworker in other messages, you might be interested in my observations. Though DIN specifies various types of reinforcement material, all the newer one I came across is ``naturhart'' --- not hardened by cold-working. The iron has enough carbon that you can harden it by cooling in water. Nevertheless, in the state as delivered, you can bend it cold to a right angle with an amazing (two or three rod diameters) radius w/o breaking. The ridges on the steel are rolled on while red-hot. That steel is not useful for making edge tools. Though you can harden it enough for making an ax, the edge will break out with a coarse grain, even when carefully heated, smithed, and tempered. But it's an excellent material for smith's tongs and some anvil tools. Application is restricted as I found it impossible to get rods thicker than about an inch. Price is about half what ordinary construction steel ST 37 costs. -- hw
Reply by ●November 9, 20092009-11-09
Rune Allnor wrote:> On 9 Nov, 04:29, Jerry Avins <j...@ieee.org> wrote: > >> The concrete is some of the hardest I have dealt with, harder by far >> than a typical sidewalk. The rebar (reinforcement bars) is interesting. >> European practice uses round bar, while American rebar is deformed to >> add ridges that increase bond strength. The rebar in the Berlin was >> deformed. Was it imported from the West? > > Don't know its origins, but the rebar I have seen has ridges or > grooves (see a picture here): > > http://fil.nrk.no/torget/wp-content/uploads/nrk_media/auto_5913/full.jpg > > Maybe the eastern European stuff didn't need bond aids: It was > usal for the old communist states to make perfect products. Their > factories - being communist and thus perfect - did not pollute, > so they did not need waste product cleaning facilities and so on. > A rebar that had the bound aids was, per definition, not perfect > so communist states would not have made them. > > A bit convoluted, but I am sure you get the idea.Yes. I've heard that before from people I had once respected. :-( Smooth rebar might have been a figment of my CE text's imagination. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 9, 20092009-11-09
On 11/9/2009 10:32 AM, Jerry Avins wrote:> Rune Allnor wrote: >> On 9 Nov, 04:29, Jerry Avins <j...@ieee.org> wrote: >> >>> The concrete is some of the hardest I have dealt with, harder by far >>> than a typical sidewalk. The rebar (reinforcement bars) is interesting. >>> European practice uses round bar, while American rebar is deformed to >>> add ridges that increase bond strength. The rebar in the Berlin was >>> deformed. Was it imported from the West? >> >> Don't know its origins, but the rebar I have seen has ridges or >> grooves (see a picture here): >> >> http://fil.nrk.no/torget/wp-content/uploads/nrk_media/auto_5913/full.jpg >> >> Maybe the eastern European stuff didn't need bond aids: It was >> usal for the old communist states to make perfect products. Their >> factories - being communist and thus perfect - did not pollute, >> so they did not need waste product cleaning facilities and so on. >> A rebar that had the bound aids was, per definition, not perfect >> so communist states would not have made them. >> >> A bit convoluted, but I am sure you get the idea. > > Yes. I've heard that before from people I had once respected. :-( > > Smooth rebar might have been a figment of my CE text's imagination. > > JerryOr you can skip the rebar altogether: http://chinadigitaltimes.net/wp-content/uploads/mt-old/r-1.jpg -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
Reply by ●November 9, 20092009-11-09
On Nov 8, 10:29�pm, Jerry Avins <j...@ieee.org> wrote:> Twenty years ago when I worked for Siemens' U.S. research lab, a group > of us went to Germany to collaborate with engineers in Erlangen and > Berlin. We took some time out to visit East Berlin by bus through a > checkpoint at the Brandenburg Gate. The Wall was still standing, but > people were hacking away at it. Our hosts at Siemens gave us each a > heavy hammer and a cold chisel so we could collect pieces of it as > souvenirs. As I hacked away on the no-man's-land side of the wall -- > there was a large gap that made it easy to get there -- a pair of > goose-stepping East German guards marched by, studiously ignoring the > activity. I stood transfixed, too stupefied to grab my camera. I brought > home several pieces of the wall and gave some away. I have two left. > > The concrete is some of the hardest I have dealt with, harder by far > than a typical sidewalk. The rebar (reinforcement bars) is interesting. > European practice uses round bar, while American rebar is deformed to > add ridges that increase bond strength. The rebar in the Berlin was > deformed. Was it imported from the West? > > Jerry > -- > Engineering is the art of making what you want from things you can get. > �����������������������������������������������������������������������Cool you got to be there. A shame you didn't get pictures, but you got actual pieces of the wall. On a remotely related topic, is the neat fact that the hyperbolic design of cooling towers (like the ones at nuclear power plants) use only straight rebars. Two sets are used where one set tilts going clockwise around the tower and the other tilts counterclockwise as viewed from above. Clay
Reply by ●November 9, 20092009-11-09
Clay wrote:> >Cool you got to be there. A shame you didn't get pictures, but you got >actual pieces of the wall. On a remotely related topic, is the neat >fact that the hyperbolic design of cooling towers (like the ones at >nuclear power plants) use only straight rebars. Two sets are used >where one set tilts going clockwise around the tower and the other >tilts counterclockwise as viewed from above.Interesting. Is that a cost issue (not having to bend them to a custom shape), or is there a structural strength benefit?
Reply by ●November 9, 20092009-11-09
On 9 Nov., 04:29, Jerry Avins <j...@ieee.org> wrote:> Twenty years ago when I worked for Siemens' U.S. research lab, a group > of us went to Germany to collaborate with engineers in Erlangen and > Berlin. We took some time out to visit East Berlin by bus through a > checkpoint at the Brandenburg Gate. The Wall was still standing, but > people were hacking away at it. Our hosts at Siemens gave us each a > heavy hammer and a cold chisel so we could collect pieces of it as > souvenirs. As I hacked away on the no-man's-land side of the wall -- > there was a large gap that made it easy to get there -- a pair of > goose-stepping East German guards marched by, studiously ignoring the > activity. I stood transfixed, too stupefied to grab my camera. I brought > home several pieces of the wall and gave some away. I have two left.just saw this video today with a danish journalist that started about 8 hours early with his hammer :) http://ekstrabladet.dk/nyheder/samfund/article1251823.ece> > The concrete is some of the hardest I have dealt with, harder by far > than a typical sidewalk. The rebar (reinforcement bars) is interesting. > European practice uses round bar, while American rebar is deformed to > add ridges that increase bond strength. The rebar in the Berlin was > deformed. Was it imported from the West?I doubt they got anything from the west at that point, I guess they were just in a hurry to get it done from what I've read they might not have been too concerned with getting it done correctly don't think I've seen rebar used around here that wasn't ridged -Lasse
Reply by ●November 9, 20092009-11-09
Clay wrote:> On Nov 8, 10:29 pm, Jerry Avins <j...@ieee.org> wrote: >> Twenty years ago when I worked for Siemens' U.S. research lab, a group >> of us went to Germany to collaborate with engineers in Erlangen and >> Berlin. We took some time out to visit East Berlin by bus through a >> checkpoint at the Brandenburg Gate. The Wall was still standing, but >> people were hacking away at it. Our hosts at Siemens gave us each a >> heavy hammer and a cold chisel so we could collect pieces of it as >> souvenirs. As I hacked away on the no-man's-land side of the wall -- >> there was a large gap that made it easy to get there -- a pair of >> goose-stepping East German guards marched by, studiously ignoring the >> activity. I stood transfixed, too stupefied to grab my camera. I brought >> home several pieces of the wall and gave some away. I have two left. >> >> The concrete is some of the hardest I have dealt with, harder by far >> than a typical sidewalk. The rebar (reinforcement bars) is interesting. >> European practice uses round bar, while American rebar is deformed to >> add ridges that increase bond strength. The rebar in the Berlin was >> deformed. Was it imported from the West? >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> ����������������������������������������������������������������������� > > Cool you got to be there. A shame you didn't get pictures, but you got > actual pieces of the wall. On a remotely related topic, is the neat > fact that the hyperbolic design of cooling towers (like the ones at > nuclear power plants) use only straight rebars. Two sets are used > where one set tilts going clockwise around the tower and the other > tilts counterclockwise as viewed from above.I take it that's a question. I doubt it despite the beauty of of the design. The crossing probably wouldn't obviate the need for circumferential reenforcement, and the bend wouldn't be difficult. A more-or-less orthogonal grid of rebar is easier to analyze. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 9, 20092009-11-09
langwadt@fonz.dk wrote:> On 9 Nov., 04:29, Jerry Avins <j...@ieee.org> wrote: >> Twenty years ago when I worked for Siemens' U.S. research lab, a group >> of us went to Germany to collaborate with engineers in Erlangen and >> Berlin. We took some time out to visit East Berlin by bus through a >> checkpoint at the Brandenburg Gate. The Wall was still standing, but >> people were hacking away at it. Our hosts at Siemens gave us each a >> heavy hammer and a cold chisel so we could collect pieces of it as >> souvenirs. As I hacked away on the no-man's-land side of the wall -- >> there was a large gap that made it easy to get there -- a pair of >> goose-stepping East German guards marched by, studiously ignoring the >> activity. I stood transfixed, too stupefied to grab my camera. I brought >> home several pieces of the wall and gave some away. I have two left. > > just saw this video today with a danish journalist that started about > 8 hours > early with his hammer :) > > http://ekstrabladet.dk/nyheder/samfund/article1251823.ece > > >> The concrete is some of the hardest I have dealt with, harder by far >> than a typical sidewalk. The rebar (reinforcement bars) is interesting. >> European practice uses round bar, while American rebar is deformed to >> add ridges that increase bond strength. The rebar in the Berlin was >> deformed. Was it imported from the West? > > I doubt they got anything from the west at that point, I guess they > were just in > a hurry to get it done from what I've read they might not have been > too concerned > with getting it done correctly > > don't think I've seen rebar used around here that wasn't ridgedI've been misinformed for years, it seems. (But then, you knew that.) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
