Attic Trusses 2

[medeek]

Has anyone else had much experience analyzing trusses (metal plate connected trusses) utilizing RISA3D?

I've pin jointed all of the web members and rigid jointed the heel and peak joints. For now I've ignored all of the load cases and just assumed one load case to get a better feel for the Axial, Shear and Moments in the various chords and webs.

Loads

Axial

Shear

Moments

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[KootK]

Surprisingly no! I actually wrote WTCA's tech note on construction loading. I can recall no instance of my labours ever having less impact. I believe that "failure" in a truss plate is usually tooth withdrawal. You retain considerable joint strength but joint stiffness goes to hell in a hand basket, particularly perpendicularly to the teeth.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[a2mfk]

What is the point of this post? Are you a mechanical engineer who is now dabbling in structural engineering?

I went to your website and read your bio, and not to be too harsh my man, but I am not sure what it is you are doing with this business or your career, and if it is ethical.

We are not allowed to assist non-engineers in engineering, and if you are not a qualified structural engineer, then we should not be helping you out.

Your post exposes a lack of knowledge of a system as basic as trusses, which is something you learn in Structures 1 and you should be able to solve simply by hand.

My educational background is a bachelor's of science in Mechanical Engineering from Brigham Young University ('98). I am a professionally licensed mechanical engineer in the State of Washington, as of December 2012, and in Utah, as of February 2014. I have spent the last few years studying structural engineering of wood frame structures in some depth, and the related commercial and residential codes.

 

[medeek]

@a2mfk

My original schooling was in mechanical engineering but I switched careers a couple years ago to the structural field, it has been challenging but definitely worth the ride.

I'm not sure what you mean that this post exposes my lack of knowledge of trusses. I challenge you to try and solve this particular truss by hand, the first thing you will determine is that it is an indeterminate structure and your method of joints or sections just does not work in this case, it can't be solved by hand. Matrix analysis is the only way to solve this truss.

Last year I programmed a matrix analsys program into my fledgling truss designer here:

http://design.medeek.com/calculator/calculator.pl

(Fink truss only)

The results match up perfectly with my output from STAAD and RISA so I'm pretty confident I at least got that part of the structural analysis right.

I just received my copy of ANSI TPI-1 2014 in the mail yesterday and was pleasantly surprised to see that there are not many changes from the 2007 standard. My truss designer is at this point an academic exercise in trying to implement all of the necessary checks per the TPI 1 in regards to lumber and plate sizing, still very much a work in progress.

My next challenge it to try and add in a rudimentary attic truss.

I know that I am recreating the wheel when you consider that the truss giants (ie. Mitek, Eagle, Simpson, ITW) already have software that does this sort of analysis and probably a lot better than mine does. The problem is that as an engineer you will never gets your hands on their software unless you work for a truss company or are an employee of the plate manufacturers.

I am not an SE but then how many engineers that do residential structural engineering are? In the state of Washington and Utah and SE is only required for certain structures so what I do is perfectly within any legal or ethical realm.



A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[medeek]

@a2mfk

I guess I'm the type of person it is hard to pigeon hole into one career or stereotype even though some people will try. I've had a very varied career, with businesses in the tech industry, building supply industry, trucking industry and native art industry to name a few. I'm an engineer but I also enjoy design, architecture, art, programming and artificial intelligence research.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[BAretired]

I have the same problem as dhengr and I am using Firefox. I haven't tried Google Chrome, but I will. It may be that Eng-Tips can correct the problem. Even as I'm typing, I can't read the left part of the screen. For some reason, word wrap is not working properly with my current browser. And even when I do a Preview, I can't read a complete line without jogging back and forth. It's enough to drive me away from this thread.

BA

 

[BAretired]

Okay, now I'm using Google Chrome and the word wrap feature is working properly.

BA

 

[medeek]

This thread probably should have been started in TRUSS engineering forum, sorry about that.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[BAretired]

Nothing wrong with having it in this forum. Putting it in another forum won't help with the display. In Google Chrome, the diagrams are much smaller than they were with Firefox.



BA

 

[XR250]

FWIW, I am an ME who became an SE

 

[medeek]

Maybe I need to change my profile description to "Structural", about every 2-3 months I get a blast from another structural engineer on this board about why an ME has no business doing structural work. The funny thing is that one of my own local mentors started out as an ME in the aerospace industry like myself and went on to become a structural engineer.

Engineering is engineering, if you want a change in course go for it. A more drastic change in course from a mechanical discipline to computer or chemical engineering might raise a few more eyebrows but even then this is a free country, the choice and opportunities are there, if you want to take them.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[boo1]

Much better to learn, study and improve skills.

 

[RFreund]

From the posts I've read from Medeek he a better SE than most when it comes to wood design. And would mostly likely run circles around most people when it comes to analysis.

EIT

http://www.HowToEngineer.com

 

[XR250]

@RFreund;

Are you guys having a bromance?

 

[ChiefInspectorJeff]

I qualified to take the national engineering exam and Architecture exam in the 90's with an Associates degree.In many States 10 years experience was the requirement.
In Florida an Engineer can practice in any field he is competent in as there is no " structural engineer " title, even though i think there should be. I don't know how many schools were teaching wood lateral load design in the past.
My brother has an engineering degree from Va. Tech.and is a P.E. and he did not study wood lateral design. The fact is school and passing the exam are only the beginning in any profession.