studiot

These are your figures, so I'm glad you 'agree' them. Again this is your figure, so I'm glad you 'agree' it. I am quite capable of working out the forces in a relatively simple lattice girder like this one. I did, however, ask you a question about the necessary information and I would have thought the least you could do would be to point me to the right page instead of being sarcastic. I also understand the working of ~RC struts and in particular their failure modes, something you seem abnormally reluctant to discuss. So no more half lectures please. You are presumably aware that the ultimate strength of grade C60 steel is half as strong again at 90,000 psi? You have however claimed that the actual stress applied to member M11 exceeded then concrete strength of 6000 psi, when the calculation you accepted shows it to be only 2/3 of that figure. Since you obviously missed it last time I will repeat this. We do not expect a component to come near to failure under normal working loads, which is why we derate things by applying factors. So consideration of factored loads is not appropriate in a failure investigation. Have you ever conducted any failure investigations? I have and I can assure you that the procedure is quite different from the normal design one. We are not asking does it conform to the code (although that question will inevitably be asked as well) when we are trying to determine what happened.

Better let's keep the discussion professional shall we? I'm trying to make sense of your calculations, but have not yet tried to wade through the 110 page pdf you linked which presumably has the information required to make my own calcs? At the moment I am at the following stage with your figures. Area M11 = 24 x 21 = 504 sq ins Area steel = 8 x 0.6 = 4.8 sq ins Aread duct = 14 sq ins area concrete = 485.2 sq ins Applied load = 1927000 lbs force If this was applied to the concrete alone compressive pressure = 1927000 / 485.2 = 4000 psi (just under) Granted I have not applied any factors, but a failure investigation must investigate ultimate conditions of collapse.

You have said this twice, but that doesn't make it either true or an explanation/amswer to my question. I don't know is that is because you are entirely missing the point, or what. Potentials act over space not time. But you mentioned forces, not potentials and forces change the energy of a body by doing work on it. I do not need a fancy differential or integral equation to know that if no work is done on a free body the energy of a body does not change.

So are you suggesting there is a solution to the circumstances presented whereby the energy can change? At last, thank you for answering the OP question. Can I take it your answer is No, Copenhagen is inappropriate? You could have said that a long time ago. I would certainly agree with you that many of physical phenomena are also described or inherent in the maths. But all this does is demonstrate what a jolly good model that particular piece of mathematics is. (and therefore why we use it). As to Mathematics itself, yes every differential equation can be remodelled as an integral equation - I have several books on the subject. But I would also council two things "Beware of all or nothing statements" They have a habit of tripping themselves up. "Beware of saying that it is a consequence of the maths and nothing more" There is more to the mathematical modelling of physical processes than that. Take 'centrifugal force' for example. This is physically evident from some points of view (models) but not others.

Basically yes. That is why the Sun's gravity was used for the test.

You have described member 11 as under-reinforced. How does (by what mode) an underreinforced concrete member fail? Edit, further why was it in so much compression? Ties are usually much longer than struts so it looks like a tie in the diagram, not a strut?

No I think the question being asked is equivalent to greedy shipowners in the past asking How many sacks of coal will sink my boat?

That is not what I asked, sorry.

I know that , but any Engineer would (should) shy away from describing the failure of concrete in compression as cracking. It doesn't. It suffers crushing failure if at all. But don't forget how difficult it is for any material to fail in compression. In order for that to happen it has to be in triaxial compression, otherwise some other form of failure occurs. The 'compression' failure of concrete cubes, for instance is (uniaxial compression) is a diagonal shear failure, and the BS rules out cube failures which depart significantly from this pattern.

Thanks to all who replied, particularly Mordred and Uncool (+1 apiece). I really hadn't considered the time aspect which makes it impossible in space time for the same coordinate points to be traversed, even if you take the scanario I proposed which was simultaneous viewing from both ends. I suppose we will have to rephrase it so that the timescale of observation is short compared to that of any material changes. I really don't know the answer to my question which is why I asked it. This is all part of my attempt to reconcile theoretical and observational / practical Physics.

Please explain why concrete in such heavy compression as you describe is 'cracked' ?

Gosh this really is a piece of string question. What country are you in? This is relevant because in some places they build to the codes, in some places they ignore them. You need to provide a lot more information about what you really want to do, and, as Bender says, about the ceiling, walls and so on.

Thank you for posting this information. +1 It will take some time to digest it. Aberdeen huh? I've just collected someone from Aberdeen at Bristol airport.

1) I don't think I said I was only concerned with solution for a single particle translating freely in space. I think I said this was the simplest solution. It is the simplest because of the second part of your statement. 2) Thank you for bringing to my attention that I missed a (very important) variable. Here is the correct equation, including Energy. [math]\Psi = A\sin \sqrt {\left( {\frac{{8{\pi ^2}mE}}{{{h^2}}}} \right)} [/math] Bearing in mind that the wave function itself, psi, does not translate - that is the activity of the 'particle', The question then arises, How can the energy of that particle change if it is (your words) not subject to any forces or (my words) not subject to any potential? Which brings me back to my question you have not answered What does your input have to do with a particular interpretation of QM as that is the OP? @swansont - any chance you could put a pointer on my previous incorrect post as I can't now alter it?

I remember doing a material failure investigation on a german super alloy (steel). The emergency repair on the bridge bearing cost £1/4 million, leaving 63 more bearings at risk on the viaduct.

Yes that's right, SJ. The problem is that light travels along geodesics. Surveyors are used to the fact that if you set up a theodolite at some point A on the Earth's surface, sight on B, and set out a row of pegs leading to B, and then move to B and set out a row of pegs from B to A there will be two rows of pegs, not one. This due to the fact that the direction of gravity at A and B will point to slightly different centres. I am just trying to get my head round the implications extending this to the universal spacetime manifold which is more irregular than the Earth. So thanks guys for responding.

I'm not entirely sure why you posted a derivation of Schroedinger, or where you are going with it? Your Schroedinger equation is only true because the potential term is zero, otherwise it is incomplete. The solution I was thinking about is [math]\Psi = A\sin \sqrt {\left( {\frac{{8{\pi ^2}m}}{{{h^2}}}} \right)} x[/math] Which I think is more useful as you can plug numbers into it. As I understand it, the method of finding this solution is 'inspired guess', which means guessing solutions, based on experience, and testing to see if they satisfy the DE or PDE, which they do in this case.

Does General Relativity imply that the Principle of Reversibility of Light does not hold in our Universe?

Coriolis only affects horizontal motion, it does not affect vertical motion. Tides are a vertical movement of water so are unaffected directly. However in order for the water surface to rise and fall, water must advect in and out horizontally. These tidals streams are affected by Coriolis, though to a lesser amount than ocean currents. This is because the biggest effects are close-to-shore effects. In the open ocean the tidal rise and fall is small as are the oceanic tidals streams. Here the local flow is small but spread over such a vast area that the volume is substantial. Close-to shore effect demonstate resonance and/or forced oscillation effects such as the amphidromic points in the North Sea. The size and timing of the vertical water movements and the direction of the horizontal ones are strongly influenced by the topography.

Well I see that you have exhibited a Schroedinger equation, but I don't see you exhibiting a solution in explicit form [math]\Psi \left( {x,t} \right) = ???[/math] That would be what I call a solution.

And yet spatial displacement was the originally proposed test of GR and the actual one which provided the first practical verification. I am aware of your longitude analogy, and am hoping to offer a fuller answer to that and your other questions, but in turn, I would also be grateful for some discussion of the OP.

Except that I was not questioning your point about the sky or its blueness. I was questioning the appropriateness of the use of the word why. Do little children ever ask any question other than why (not).

Really? Why do you say that? And how does that pertain to the OP? Or, if you like, how does any bending in the ct direction allow light to go round a solid obstacle?

What a refreshing attitude. +1 You should go far. Welcome indeed.

Why is a rather overused word, which sometimes oversteps its boundaries. Let me change your question slightly to Why is your car blue? Answer 1) Because I Iike blue best. Answer 2) Because it reflects the non blue light present in sunlight. Answer (1) is a motivational answer and not Physics. Answer (2) is a Physics answer but would not be more correct to ask "By what mechanism...?" IOW how (come) ?