×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

P.E.'s working for wood truss manufacturing company

P.E.'s working for wood truss manufacturing company

P.E.'s working for wood truss manufacturing company

(OP)
I was just curious if there were any P.E.'s out there who work for a truss manufacturing company and who seal wood truss shop drawings?  

RE: P.E.'s working for wood truss manufacturing company

I am not, but know of a few.

RE: P.E.'s working for wood truss manufacturing company

(OP)
I am a P.E. working for a truss manufacturing company.  I currently do not seal drawings, however, am looking into doing it.  I was hoping to find some information/direction regarding this.  I would be interesting in finding information on how the typical engineering software analyzes the trusses.  I know that ours uses the Purdue Plane Stress Analyzer method, but haven't been able to find much information on it.  Are there any books/literature out there that would have examples of a wood truss design using this method?

RE: P.E.'s working for wood truss manufacturing company

I have not heard of that one.  I think MiTek uses something different and that is the one I am most familar with.  Not sure about the analysis though, maybe try contacting the software co?!?

RE: P.E.'s working for wood truss manufacturing company

After looking over the PPSA literature I'm fairly certain Mitek uses the same basis in stress factorization. It's not my field of expertise, I'll ask a friend of mine whom used to be in Mitek's Engineering dept to post regarding it.

RE: P.E.'s working for wood truss manufacturing company

Stan Suddarth did some design work for TPI many years ago using PPSA. Today programs are largely based on matrix/stiffness methods but there are empirical formulas that TPI has added to the analysis (mostly bearing conditions).
You can find the standards at http://www.tpinst.org

RE: P.E.'s working for wood truss manufacturing company

(OP)
Loui1,
Thanks for your reply.  The WTCA technote that you read is referring to the truss placement plan.  They are saying that truss engineers should not seal these because most of the time they don't create the placement plan.  They only seal the shop drawings for the individual trusses in the plan.  It is common practice to always require sealed shop drawings for wood roof trusses.   

RE: P.E.'s working for wood truss manufacturing company

The following is copy/pasted from another thread -

The Idaho PE board issued a statement recently where they propose a more "proper" format for wood trusses (whether gluelam or pressed gangnail:

Basis of Design

1.    Premanufactured roof trusses are an engineered system - that is, each truss has a specified location in the overall structural system.

2.    The premanufactured roof truss system is both a vertical and lateral load system.

3.    The lateral load forces must be developed by the EOR and given to the truss engineer to design (drag truss load, collectors, etc.).

4.    All truss-to-truss connections are the responsibility of the truss engineer.

5.    All drag load (horizontal truss transfers) connections between the truss and the structure are the responsibility of the EOR.

6.    All truss-to-structure (walls or beams) connections are the responsibility of the EOR.

7.    It is the responsibility of the truss engineer to develop the loading required to implement the requirements of snow load Appendix A.

8.    It is the responsibility of the truss engineer to review all of the EOR’s design specifications, roof truss support, and drag details and to incorporate these requirements into the engineering design of the roof truss system.


Required Information from Truss Engineer:

The truss engineer should develop a truss layout plan for the truss system that clearly indicates the truss vertical support conditions, truss-to-truss connections, drag trusses and collectors, and any other field-installed reinforcement, including field-installed top chord reinforcement at eaves necessary to execute the truss system design.  The truss roof framing plan should be sealed by the truss engineer and be included with the individual truss cut sheets.  The truss engineer should also provide proper supervision of any truss company technicians.

RE: P.E.'s working for wood truss manufacturing company

I work for a company that designs and fabricates glulam trusses.  Although I am a registered engineer along with others in our company,  we don't certify any of our designs.
If certified calculations or drawings are required we use outside consultants.

My reccomendation would be that you don't  seal any calculations or drawings unless your company carrys errors and omissions insurance.  

Regarding the PPSA program my understanding is that it uses a stiffness method based on a virtual energy formulation.  The company I work for has used the first edition with some modifications for around twenty years.  We have found the program to be very reliable.

My understanding if that at one time the program was widely used by the press plate truss industry.  I am not familair with how that industry used the program.  So I don't know if they used the basic program for truss analysis  adding on other code to select truss plates member sizes ect.

At this time I don't believe any one is supporting the program.   

RE: P.E.'s working for wood truss manufacturing company

I would disagree with the Idaho PE board that premanufactured roof trusses are an engineering systems.  The trusses are individual componets of the system.  The individual trusses become part of the system when they are joined togther by roof sheathing, drywall when used and bracing.

I wonder if the Idaho PE board would consider steel bar joists as an engineering system, requiring the joist engineer to sign all joist placement plans?

What is the practice out there regarding steel joists?

RE: P.E.'s working for wood truss manufacturing company

(OP)
RARSWC,
Thanks for your response.  I have been told that if you are a P.E. sealing a shop drawing for a product that you manufacture (i.e. a P.E. sealing a shop drawing for a wood truss that is manufactured in house), then your liability insurance will cover you.  That is you do not need an errors and omissions policy.  See thread1066-145337.  Do you know of any information contradictory to this?    

RE: P.E.'s working for wood truss manufacturing company

CJSchwartz

I looked at thread1066-145337, and it raises a good point.  I think to feel safe, you might want to contact a lawyer withe experience in engineering litigation.

You might want to contact your state engineering board.  The gray area is, are you sealing a component drawing or a design drawing that uses component produced by the firm you work for.  As you already know from this forums, there is a lot of disagreement as to whether you are sealing a component or a system design.

One thing you should check into is whether or not your companies liability insurance would cover you ten years from now when you no longer work for the firm.  It is my understanding that errors and omissions insurance would at least cover your legal fees.

RE: P.E.'s working for wood truss manufacturing company

(OP)
RARSWC,
I contacted the Ohio State Board of Registration for Professional Engineers.  Their reply was "If the drawings/design was done under your direct supervision (see OAC 4733-35-07) you can seal them. If they were not, the engineer who was in responsible charge of the design must seal them."  

This reply seems obvious.  I take it they don't have any specific regulations with regard to roof trusses.  In our industry, it is common that the engineer sealing the shop drawings does not design the truss.  They simply review the design with their analysis software and then seal it and send it back to us.

It is generally accepted in our industry that we are sealing a component drawing (at least from the truss manufacturer's perspective and the Wood Truss Council of America).  The reason we do not seal truss placement plans is that we are not taking responsibility for the system, only for the truss componenets on the layout.           

You make a good point with whether or not our liability insurance would cover me if I were to leave.  I will definitely check into that.        

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources