Hodge is more or less correct on his other responses, but I think the question above is about whether or not the theater’s insurance would cover. I am not an insurance agent, but I doubt it.
Copper isn’t a very common structural material. Based on a quick check of material properties, I’d say at least twice or three times as thick, depending on the alloy. If it were my body part, I’d stick with steel.
Funny. I’d have gone into computer science.
**So here’s my big-picture question: is there any building technology currently in use that you think is being pushed beyond its reasonable limits? IOW, what’s the next Tacoma Narrows, in your opinion? **
[/QUOTE]
I think that with the current state-of-the-art in analysis and materials, that another Tacoma Narrows is unlikely. I think that the Biggest Unknown is in seismic design. Every time the earth shakes, we find out more we didn’t know before.
Other than seismic, I think the increasing emphasis on speed of design and construction will probably lead to another Hyatt Regency. The Hyatt Regency wasn’t just one design mistake, but a string of bad snap judgements and missed warning signs, mostly owing to a tight construction schedule.
A lot of pre-computer analysis was done with very clever approximate methods, such as Portal Frame Analysis and Moment Distribution, both of which are still taught in school (or at least were). These methods required a lot of calculation, but not as much as a stiffness matrix method. Legend has it that SOM ran a computer model of Sears Tower once (and only once) to verify their hand calculations. It cost $10,000 to do. In 1972.
Ah, yes, vibration. I am not a bridge engineer, so I can’t speak to vibration in bridges, but a floor system of steel beams in the 22-30 foot range have a natural frequency that resonates at most people’s walking pace. If the system is light enough, your walking will cause it to feel like it’s bouncing. It’s especially noticable in open areas such as shopping malls, where ther damping effect of furniture and partitions is minimal. I imagine that certain bridges may resonate with the frequency of a truck’s suspension rebound in a similar manner.
I’m a building engineer, so I don’t usually deal with those things, but we all get the same magazines. Based on those, yes, there is quite an industry based on inspecting those things. Of course, writing a report is one thing. Having the DOT pay to do anything about it is another.
Definately designed by an architect!
Finite elements. This is the technology currently used to model structures on computers. This technology is very powerful but unfortunately allows unqualified people to perform complex analysis without really understading what they are doing. This is very dangerous and we see screwed up analysis all the time. Good thing structures have big factors of safety.
I believe the most likely next tacoma narrows will be a long-span roof (such as a stadium) collapse where the analysis, performed using finite element, was performed improperly.
EMRC/NISA is a general purpose program that has shell (thick, thin and hybrid), beam, solid (4 and 8 node) and gap elements (amoung amny others). It can model pretty much anything.
SAP2000 is intended to model only beams, although it does have shells for shwar walls and diaphrams. It works great for buildings but miserable for anything else. Much faster than EMRC NISA when modeling buildings, however.
culture’s right. There have been several instances of structural collapse (Hartford Arena comes to mind) caused by the inability of the engineer to translate the idealized computer model to the real-world structure and vice versa.
Mario Salvadori’s Why Buildings Fall Down is an interesting and accessible read on the subject.
Texas A&M and the Mental Institute for the Touched
Gordon’s Structures, or Why Things Fall Down is better IMHO, but both are a good read. Gordon’s book covers civil and mechanical engineering concepts. Mario Salvadori’s Why Buildings Stand Up is also good. Wearne’s * Collapse: Why Buildings Fall Down* gives several interesting in-depth case studies but is more technical and of limited interest to non-engineers.
I keep all four on the desk right in front of me to keep these things in my mind. I spend a lot of time investigating structural failures in my practice.
Thanks to Finite Elephant, Hodge and Others for the backup.
You’re welcome, culture. I apologize for any thunder-stealing.
And BTW, I went to Illinois. Twice. I highly recommend grad school as a means of going into career stasis during a recession.
And since I’m cleaning up loose ends, my firm uses RAM, RISA, Robot, SAFE, and the usual assortment of one-trick programs. I’m in the Rust Belt, so our practice is mostly in steel.
We do this all the time. At some of the mega concerts, the producers want to hang 20,00 to 50,000 pounds from our carefully designed stadium roof. Therefor we get hired to supervise the rigging. We even get to watch some of the concerts from the ceiling framing to monitor things.
Opps, forgot about SAFE. We use that too, as well as RISA 3D sometimes.
My minion did the same thing (UICU/two times). He is working out pretty well so far. UI was one of my top five picks for grad school. Could resist the call of the east coast however.
I’ve read, and love, both of the Salvadori books, and will now try the Gordon.
Interesting that the technology you identify as problematic is something used in creating a design, rather than something intrinsic to the design itself.
I live in Chicago. I am not a paranoid nut, however I keep hearing about this fault line in southern Illinois. How screwed would we be here in Chi-town, if a big one hit down south?
A.) I live in a simple wood frame house, an old one.
B.) How about our downtown?
Thanks.
Which brings up a good point. Why would culture hate architects? For that matter, maybe he can enlighten us as to the division of responsibilities on a building project. It seems like the architect gets most of the credit, but the structural engineers have to vouch for the solidity of every cubic centimeter of the finished work. Do architects and s.e.'s often work together in the same firm, with each carrying out different responsibilities.
You are probably thinking of the New Madrid fault centered in Memphis. If the big one hit, you will be safest in a one-story wood frame house that has wood siding. Old multi-story masonry buildings are the worst. Modern hi-rises are pretty safe as they tend to be more carefully engineered.
How bad Chicago will get it when the New Madris fauly goes (and it will) is very hard to say. However, Chicago is rated a seismic zone 1 which means if you do get large ground motion in chicago you are screwed as the buldings are not built to resist it (However, zone 1 also implies geologist think you will not get large ground motions). Memphis, however, is doomed if they get a magnitude 8 quake, because they have not had a signficant quake since 1830 so they citizens tend to forget it can happen.
This is kind of a runnuing joke in the industry. Architects and SEs have a love-hate relationship. Architects are vital to gettinga building built, but so are SEs. SEs feel the architects get too much credit for the results. Look at the plate on most buildings. It list the owner, architect and contractor, but requently the SE is left off. Architects get larger fees than SEs. The architects is normally the prime design professional (i.e. the SE works for the architects), and SEs feel this gives the architect too much control over the SEs design.
However, overall, the architects and SEs get along just fine as they are our best clients, and it is hard to hate the hand that feeds you.