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Truss engineering - Mitek verus Truswal

Truss engineering - Mitek verus Truswal

Truss engineering - Mitek verus Truswal

(OP)
I run 2 design offices. One uses Mitek, and the other uses Truswal. The analysis between the two is significantly different. Has any PE who does NOT work for a truss company or the companies above ever sat down and compared the two? Is one more accurate than the other? Some differences are:

Wind analysis - C&C, MWF, or both?

Metal plate analysis - All truss joints pinned or semi-rigid joints?

I would really like a non-partial opinion.

RE: Truss engineering - Mitek verus Truswal

Ask the code authors, bet they are non-partial!

RE: Truss engineering - Mitek verus Truswal

I have worked in the industry.  Any trick we could find - we would use to reduce forces and therefore plate sizes on common designs.

In actual practice - we would often increase the size to make us(me) feel more comfortable.

Get with their engineers and find a comfort level.

RE: Truss engineering - Mitek verus Truswal

A lot depends on their algorithms and what they base their numbers on.  I know Alpine and Mitek use different methods from ASCE to get their numbers (simplified vs. building of all heights). You also have a bunch of different settings that the computer operator can select, all of which change the numbers and are much more of a factor than the software provider.  You can, however, force them to provide you detailed printouts for any truss which will show all load cases and results.  If you are persistent enough you might even get a chance to talk to an actual engineer.

RE: Truss engineering - Mitek verus Truswal

As an impartial code professional in the field of fire protection engineering, one extremely important factor that is missed when designing trusses is the failure rate when exposed to fire.  Truss failure occurs much earlier during a fire than solid framing materials used in the past and this factor is not taken into account by designers, builders, and many building code groups.  The results are increased property loss and more importantly increased life loss to building occupants and firefighters.
Keep this in mind when specifying materials and methods of manufacturing trusses.
Thank you.  

RE: Truss engineering - Mitek verus Truswal

Tend to agree with Brynesf but I have found many case that all that was left standing was the roof trusses while the steel beams had bowed, deflected and started to melt.

In a very hot fire - the steel will go quite quickly while the wood will only char for awhile.  Ususally the trusses have much more protection - drywall.  And if the fire fighters get on it quick enough - which they usually do - the steel will often fail before the trusses.

That said - fire fighters must be aware that any house built in the last 50 years probably has trusses.  The latest concerns are the use of floor trusses and wood I-joists that may not last as long as say 2x10's or 2x12's

RE: Truss engineering - Mitek verus Truswal

(OP)
This thread was just to question the differences in software, not fire. brynesf, if you want more information regarding wood truss performance, see this link.

http://www.sbcindustry.com/fire.php

Contact any truss supplier and they will provide you with the Carbeck CD listed on this link free of charge.

RE: Truss engineering - Mitek verus Truswal

I take it that most of you are in the truss manufacturing business and not the structural consulting business.  We work a lot with architects preparing the structural design for buildings and have on many occasions needed to know the end reactions, uplift, etc. for different truss designs.  This information is routine if you are ordering pre-engineered roof trusses.  I feel quilty asking the local truss manufacturer to run a truss design (usually Mitek software)for me without offering to pay them for their time.  Is there a software package available from Mitek for structural consultants.  This can be very frustrating at times.  I was told by Mitek engineers four years ago that a version for consultants would be available in one to two years and have yet to see it.  I'm not about to go out and start fabricating trusses (the current software is geared to lumber yards that make trusses).

RE: Truss engineering - Mitek verus Truswal

There is a wide range of models used in the truss design software out there.  MiTek models chord breaks as fully rigid,  Alpine has a semi-rigid model and others still model the joint as fully pinned.  Moment and load distribution can be dramatically different depending on the model used.  These differences will effect the lumber grades and plate sizes needed to resist the local forces at these joints.  The industry has not been very successful in standardizing the modeling methodologies.  Until more standardization can be implemented into the industry (through the ANSI/TPI 1-x standard) I believe you will continue to see different answers from the various software packages out there.

RE: Truss engineering - Mitek verus Truswal

Being a long time designer using Truswal (17 years) and having worked closely with others that have used Mitek, the two software packages are neck in neck as far as analysis, from what I can tell, with Truswal being a bit more on the conservative side. To me the difference is made in support and the team of professionals willing to bend over backwards to rectify just about any situation that arises. To me this elevates Truswal (ITW-BCG) above all the other competitors. Add to this the diligent, cutting edge, user assisted software development and I would chose the personal touch of Truswal for any business interested in producing quality, trustworthy components.

RE: Truss engineering - Mitek verus Truswal

Can any one please provide the link for Mitek software.Appreciate the help.Thanks

RE: Truss engineering - Mitek verus Truswal

The website for Mitek is www.mii.com, and for ITW Building Components (Alpine and Truswal) is www.itwbcg.com.

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