Newmark's Numerical Procedures 6

[BAretired]

I have referred to Newmark's Numerical Procedures on some of the Eng-Tips threads. Attached are a few notes illustrating Numerical Procedures in a few simple cases. These notes were prepared by a student of R. N. McManus who was himself a student of N. M. Newmark at the University of Illinois.



BA

 

[ishvaaag]

Thank you very much, BAretired.

 

[paddingtongreen]

Thanks BAretired, that was a walk down memory lane.

I think I posted this response yesterday but it isn't here, I'm must be getting past it.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[dhengr]

BA:

Very interesting, I haven’t seen or thought much about Newmark’s methods in years. In the mid 60's I spent a quarter in grad school course learning about and using those methods. The Prof. who taught that course and some of my other computer applications courses was from the Univ. of Ill., and as I recall he worked with and learned from Newmark. Over the years I used these methods to solve some fairly interesting problems. We just had no other convenient or practical methods to handle some of those problems. Of course, we didn’t have all the in-house computing power or software that’s available today either.

ishvaaag... look for “Numerical Analysis of Beam and Column Structures,” by William G. Godden, N.M. Newmark, editor, Prentice-Hall International Series. This was the text we used for the course.

By the way, you lost several of your posts the other day, at the same time. The one where you made the comment on the lost post had to do with pinned-pinned or pinned-roller/sliding beam or truss reactions on a wood roof truss, where someone went off on a tangent about welded steel bar joists not being pinned-sliding. The other lost post was on the ME forum, “How to Explain von Mises?”, and I thought you hit the nail on the head on that one, it involved a simple wall bracket design. This guy needed FEA to analyze this simple wall bracket, and then couldn’t explain the Von Mises stresses output, and didn’t have the vaguest idea what he was talking about. He wasn’t getting much help from most of the followup posts either. He couldn’t figure out how to present his results to a structural engineer in a meaningful way, so the engineer who knew what he wanted to see, could use the results. You told him that since he didn’t know what he was talking about maybe he should give up trying to explain it, and get some real help so he understood it himself first.

I wish we had a little better idea who we were talking to, and what their background was, on any given question. Of course, sometimes it’s pretty obvious what they know, and don’t know, by the nature of the question and the banter back and forth, witness the wall bracket question. My concern is that some of these people use these forums as a crutch, rather than doing a little book learnin on their own time, which should be a part of their own advancement effort. And then, we actually spend more thought and time responding to an ill thought out question than the OP’er has spent understanding and formulating his own question. Do companies understand that these kinds of questions, by their engineering staff, are floating around in the ether? Are these people designing real products and structures which could fail and cause damage? Why don’t they have local mentors and why are they embarrassed to ask their boss these questions; my standard rant?

There appear to be some pretty bright younger people involved on this forum, and I could get excited about helping them with whatever I could contribute. That probably wouldn’t be the latest version of some clause in the bldg. code (the latest bldg. cookbook recipe), or the latest wrinkle in some fancy new version of software. And, experience teaches all of us that sometimes we need one of our own peers to help us see the trees for the forest, on a given problem of our own. There certainly seem to be some pretty smart older guys who have a fair amount of experience and a pretty good handle on how structures work and act, and what it takes to make a good design and structure. These older guys also seem more than welling to help. But, what I see in some of the questions scares the hell out of me; are we helping someone with just enough knowledge to get himself into big trouble? When are we aiding and abetting the furtherance of the practice of engineering by people who should not be pretending to practice engineering; and when are we actually offering meaningful help to someone who knows what to do with it. I think we should start an ‘old dogs’ branch of this forum, since I, for one, am having so much trouble learning new tricks. We can call it “Sage Advice.”

 

[hokie66]

dhengr,
Your thoughts are held by many others on the site. I declare you officially now a member of the 'old dogs' pack.

 

[BAretired]

I'm not sure if I am old enough to be considered one of the "Old Dogs", but I have been meaning to post this material for some time. The reason it has taken so long is that my scanner is very slow...a lot like me.

The Newmark Numerical Procedures are useful in solving a variety of problems, particularly buckling problems which I find are not well understood by members of this forum.

Computers are wonderful tools and I have been using them since the mid 1950's when my boss first allowed me to attend a number of lectures on one of the earliest computers, the Royal McBee LGP-30.

It was a very basic machine requiring an inordinate number of steps to get to an answer, but I was extremely impressed by the way the instructors were able to read the paper tape output...an ability which I never did acquire because the technology improved very quickly beyond that point, making it unnecessary to continue with such a cumbersome technique.

Even today, with all of the wonderful programs available on modern computers, I still find the old techniques useful in zeroing in on a problem. And the Newmark Numerical Procedures are among my favorites.

BA

 

[rowingengineer]

BA,
Nice reference.

dhengr/Hokie,
You know what they say; if you’re not the lead dog the view never changes.
Nonetheless, while your concerns are valid, I also think that possibly, there is an alternative view. Having watched a graduate engineer that had no mentoring during his development years and refused to do after hour’s research or study, nearly send a company to the wall, both the client and the company. Before you say why didn’t you help him, this happened over a decade ago and he was a geotechnical engineer, left this office to pursue a structural career after the event.

Given the above this my view is a little bit more positive, I think that encouraging these engineers to at least look at the problem a little more and give them references for design. Maybe we can help ensure that a young engineer doesn’t design the foundations for a 40million project (a lot of money back then) thinking that all the bored piers need to be designed for is vertical load, as shear can be taken by the soil (mangrove mud) adjacent the pile caps. They way in which we can do this is by pointing flaws in the thinking, providing references and reviewing answers ect.

Maybe we do need to ask for more information sometimes, but truth is that the OP often never returns, and so that other can gain from the experience we make assumptions.


Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[paddingtongreen]

How old is an old dog?

Until I did my national Service, I had one day a week to go to Westminster Tech. When we got to statically indeterminate structures it tied in to what I was doing at work. We learned Professor Hardy Cross' Moment Distribution and I used it. We learned slope deflection, and I used it. I learned column analogy, semi-graphical integration, virtual work etc. but I wasn't allowed to use any of them because nobody remembered how to check them.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Ron]

dheng...I'm guilty! I was the one who derailed the timber thread by going off on a tangent. BA pointed it out to me and I apologized,red flagged the post and asked management to delete my post..apparently the knife slipped during its surgical removal! Even some of us who might be considered "old dogs" need a little redirection occasionally.

I agree with your comments. Being involved in the forums is both frustrating and rewarding. I, too, am surprised by some of the questions and answers. There are quite a few sharp younger members, who do their research and often come here for confirmation. Unfortunately, there's also that faction that's too lazy to research anything, are clueless of the concepts, and just want to be spoon-fed an answer. Often times they don't have any idea if the answer is on the right track or not. Fortunately, the premise of the forums is one of peer review, so "wrongs" often get "righted".

BAretired....thanks for the redirection and for your attachment to this thread....made me want to pull out my sliderule!

 

[Lion06]

dhengr-

I was one of those young engineers who used this forum to get a lot of questions answered and gain a lot of knowledge in a relatively short amount of time. I feel like I recognized the importance of doing my own homework before posting questions (and even after posting questions and getting answers), but I often posted to get a second opinion or just for topics I was trying to understand in greater depth than learned in school (that sometimes had nothing to do with a project I was working on).

I often did ask questions of other engineers in the office, but didn't want to overwhelm them with the shear magnitude of questions I had (I'm sure some will remember how many questions I used to post). I also recognized that this forum allows the question to be out there and people can respond at their convenience.

I agree that this forum shouldn't be used as a crutch, but I find this site invaluable (I might actually cry if it were to go away........ well, maybe not cry, but you get the point). This people on this forum have contributed at least as much to my mentoring as my firm, and I'm truly grateful to every one of the elder members who've answered (sometimes foolish) technical, often very nuanced questions.

While I'm wriitng this, I'd like to take the opportunity to thank all of the experienced guys who've contributed to my learning here. I'd list names, but don't want to leave anyone out and I'm sure I would.

Thanks All!!

 

[ishvaaag]

Thanks, dhengr for the reference. I always love the old practices (and tales, we are the children of such things) and am haunted on how very old ideas like Euler's on buckling or Coulomb on earth-push resist so well the wear of time. I have deep and almost religious respect for lots of people that not only developed 200 years ago theories that we need to apply today and some of these I barely manage to grasp at some basic level. I am more even so because some of them (like many artists on many fields, by the way) produced such things in harshness maybe only comparable today with the unimaginable lack of focus that living in a modern society almost automatically produces. And this is also suffered by impressive amount of young and not so young talent with basic social acknowledgement that is producing the awesome software that will allow more thorough understanding (am not so fond of consensus) of the behaviour of the structural items we deal with.

I am not much preocupied by the fact of some advice maybe help in the way of an error; for apart from the one asking the question the beautiful thing of a forum like this is that the answers stand in time for others to read; and on the other hand, always has been good to have a helping hand, I, like pedagogue Peta Penson, think that people use to make good choices giving their circumnstances, and a good answer here will make generally more good than bad, even if partly misunderstood.

 

[Ron]

hokie66/rowing engineer...there's a thread referencing wind load under ASCE 7-05 that both of you should check. There is a secondary reference to AS1170.2 in ASCE 7 that might shed a little light on the issue. I post this here only because I don't know if either you would bother with a thread referencing ASCE 7 otherwise.

BA...pls. forgive the interruption of the thread.

 

[hokie66]

Ron,
I'll have a look, but you are correct. Any reference to ASCE7 gets bypassed by me. AS1170 is enough aggravation.

 

[rowingengineer]

Ron,
I'll have a look as well, but again, would never open a forum with ASCE7 in the title.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[dhengr]

rowingengineer>> I’m proposing old-dog teams made up of single dogs, pulling side by side, so we each have a decent view. I’m not sure I want to look only at your opinion on the whole trip. Your comment reminded me of another saying ‘opinions are like a$$ holes, every one has one, or has his very own.’

All of this talk about slide rules, slope deflection, moment distribution, (give me a moment to redistribute my thoughts here), you guys are making me downright sentimental and nostalgic. You’ll make me all un-grumpy and fuzzy if you keep this up. Virtual work, does that mean that in today’s virtual world, the computer will do all the work, and I can just sit here and don’t gotta think? One of the things I really liked about my slide rule was that I didn’t have to recharge it during the middle of a test or assignment. And, I never once heard the oft repeated refrain, “sorry boss, the system’s been down all morning.”

Ron>> I wouldn’t have red flagged your comments or train of thought; I actually thought I understood the point you were trying to make, even though you selected stl. bar joist as your example, when timber trusses were part of the topic. I thought the type of material was irrelevant, we were talking about a bending member and its support conditions. We were taught that on simple beam type structures (beams or trusses) you wanted both reactions to rotate freely (pinned, not fixed rotationally), and you wanted one reaction fixed wrt translation along the length of the beam (truss), and the other reaction free to translate along the beam length; so as to keep the beam in place, but not introduce secondary reactions or stresses which our analysis methods and formulas were not intended to account for. In fact, as I recall BA was involved in an exchange, re: scissors trusses and their thrust at the top of their bearing walls, not normally a pinned-sliding reaction situation, at the same time you were typing your’s. And, you just used the example of a string of three or four bar joists, in line, and welded to beams, and the potential of some side thrust at the last beam loaded from only one side. Both of you were making exactly the point that I thought was germane; we don’t always comply exactly with the assumptions which are associated with the theory and our analysis methods, and we should know and remember this, and know when violating these assumptions could hurt us. Although, ignoring this could be more consequential on a large timber truss, near the bearing joints, than on your bar joists.

StructuralEIT>> Based on what I recall of your posts, off the top of my head, I don’t think you fit in the crutch group, but rather in the do your own homework and bright young fellow group. I suspect I could enjoy interacting one-on-one with you, and that it could even be fair exchange if you helped me with what I haven’t been able to keep up with on the computer and software front. I think your post above indicates a good understanding and use of this forum. You can see more of what I think about mentoring, etc., if you wish, by looking at the thread, “maximum stability angle” (404-265967) on the ME forum, late FEB10. There should be no embarrassment in a young engineer not having seen every situation or having questions, however, knowing and trusting your local mentor makes this exchange easier.

I take no pleasure in someone looking dumb when they ask a question, that’s why you keep hearing ‘think a little bit before you ask a question.’ Look in your own text books first, so you are up-to-speed when you come to us, with the questions. My sense is that young engineers get a very good experience when they go to work in rowingengineers’s office; witness his Grad Manual PDF thread (507-267373, *****, stars well deserved), and he gives them a copy of Fiona Cobb’s pocket book too (not a fashion knock-off either) and the fact that he weans them off of FEA until they prove they know what they are doing. My lament when I see some of the questions asked here, is that more young engineers don’t get that better mentoring experience as they start out. Many of the questions here speak of someone wandering-in-the-dark, not having the vaguest idea what they are doing, and desperate for help. My concern is not that they will take my job, or that I am a P.E. and you’re not (protecting my turf), so you shouldn’t be doing this. It is that if they have no idea what they are doing, should their product be foisted on an unsuspecting public, or worse yet that it might fail, for lack of good engineering, and hurt someone. And then, as we try to answer there question, and they go back and forth for their lack of basic understanding, are we acquiescing to, or worse yet, promoting this kind of poor engineering, and this public opinion (and some companies opinions too, apparently) of the significance of good engineering. I have had some draftsmen who did a fair amount of our basic engineering. With a little guidance, they were very good and trusted engineering assistants, and except for lack of formal college education did fine engineering. I have also worked along side some P.E.s who I didn’t want doing any engineering on my projects.

 

[Ron]

dheng...nicely said. Thanks.

 

[rowingengineer]

dheng,
You don’t have to worry about me in the old dogs pack, I don’t qualify. Too young at heart I believe.

“sorry boss, the system's been down all morning” There is nothing that eats at my wits more than when a college refuses to work because there computer is down, especially when the solution can be found with a few hand cals in half an hour. or they could be reviewing the construction process to see if what they are designing can be built.

As for local mentors, I can see your point in the post (maximum stability angle). However I think you get another award for the longest posts. , I have to point out that really the problem isn’t with the forum in this regards but more in the way in which the engineering world is thinking at the moment is some firms.

To state what I mean I will recount an event from the GFC.
In my past firm we had a good mix of engineers, 3 senior, and 3 junior. The designs for the office were of a mixed Varity requiring a good knowledge of all things solid. When the GFC hit, 2 of the 3 seniors were let go, and the juniors were promoted. The two senior engineers had spent the best part of four years training these juniors to a point where they could be considered an engineer.
However the side effect from being let go, is that these two senior engineers have decided to not mentor anymore, only reject designs out right is they don’t conform. They are now scared that if they train people they will get replaced and I am starting to see it in many different companies. This is where engineering is going to cut its own legs off.

Engineering companies are now thinking that bums on seats means something, we have 50 bums on seat such now we are a great company. This is the problem; this is where errors in design are going to grow with this attitude.

I am currently inspection man (last weeks of my current employment), and I have to say, that most of the projects I am inspecting have a missing link in the design process. Simple errors, like stopping the PT 500mm from the wall and forgetting to reinforce the last 500mm to 1000mm with normal shear reo (in this case they forgot both the shear and extra tensile reo). Designing a building with a suspended slab on ground against existing buildings, specifying the tiltup to be erected after the slab is poured and forgetting that you need to design the slab for the 160t crane or you cannot then have a 160t crane drive on it.

I could go on, but I shall stop, but let’s just say there is a stack more of these types of problems. This si the way of the engineering world, I swim against it and hope others do to, because I have a feeling in a few years builders and clients are going to start to realise this and then companies will reverse the trend, and the senior engineer title will start to mean something again.


Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[KootK]

I'd like to second StructuralEIT's sentiments regarding the mentoring value of this forum. I've been using it since I started back in 2000 (I was AdamP back then).

Sometimes I think that those who have been fortunate in the quality of their engineering experience don't fully appreciate the predicament of those who may be less fortunate.

I've worked as a member of a two person structural department, an eight person structural department, a thirty person structural department, and now an eighty five person structural department. Depending on where you're at, a young engineer can face the following difficulties:

1) At a very small outfit, there simply may not be very many "grey hairs" available to mentor you and;

2) Some small/medium firms specialize in particular types of construction (wood, precast, etc.) to the exclusion of others.

I've always considered this forum to be the "great equalizer" when it comes to engineering experience. You've got access to a bunch of old dogs even if you've never met one in person. You can also glean experience regarding structural systems that your firm doesn't typically deal with. You don't necessarily have to work at a huge generalist outfit to get first rate mentoring.

It amuses me when, every now and then, I'll find myself advising a junior engineer regarding a system that I haven't actually used myself yet. I'm able to do that, in large part, because of what I've learned here.

Like SEIT, I am indebted to the other members of this community in a big way. I plan to pay off that debt by contributing here until the ravages of age render my keyboarding hands useless.

 

[dvd]

I appreciate the download on Newmark's procedures. I think there is value in using these methods in conjuction with spreadsheets.

The conversation seems to have moved on from that, and I would like to add to that.

I think that there should be a 30-day waiting period on Eng-Tips before new members are allowed to post. If you look at most of the student and/or lame posts that are made, they are from someone who has gotten access on that same day. A cooling-off/warming-up period would help to avoid many of these posts. I also think that student posts have a place on here as long as they are properly framed.

 

[BAretired]

dvd,
I agree that the numerical methods presented above would lend themselves very nicely to the use of spreadsheets. I do not have an example to show you, but it would not surprise me to learn that it has already been done.


BA