ps

I meant, if I suggest what I think is a better repair, that shifts liability to me. So what to do?

AELLC....just reject it as insufficient and have them re-submit a different proposal. Keep rejecting until you're happy with it. You don't have to design the fix...they do as a delegated engineering function.

Ron,

Thanks, that sounds like a smart plan.

Agreed

I looked at the truss calcs. The reactions show only about 1/4 of what I calculated. I thought truss software was very automatic, I wonder what happened?

Quote:

I thought truss software was very automatic, I wonder what happened?

It isn't the software - it is the user of the software.

So many of these pre-fab'd wood trusses are punched out by local "techs" who then send the print-outs to some PE in a far away land who seals them.

I once investigated a hog barn in northern Iowa (in the middle of winter) where the roof had collapsed under unbalanced snow on a gable roof.
Windward load was about 5 psf. Leeward roof snow was about 3 ft. deep. The truss shop drawings were developed with a 20 psf live load.
Ground snow in this area was about 45 psf so I think someone didn't know what they were doing.

They had the loads exactly right. I thought truss software functioned like RISA FLOOR to automatically figure the load from each truss connected to the girder in question.

But it is true, you would think the tech and the PE would have noticed something was not copasetic, more like septic.

I even gave them a few hints on my drawings, like bottom chord of this girder shall be(3)- 2x8 minimum, post at right is a 6x8 DF-L#1, post at left is (4)- 2x6 DF-L#2, ftg at right is 3-6" sq, ftg at left is 3'-0" sq.

I am surprised the software did not take care of it.
Sounds hard to fix
Big column in the middle of the family room is an option :>

Keep us posted, and how soon they try to blame you, for not catching it at shop drawing approval.

The fix so far is threading a 5-ply girder thru the stub trusses about 11" into the span of the common trusses, and they have this idiot detail to cut the stub trusses web diagonal and put in truss hangers - here is the detail

• http://files.engineering.com/getfile.aspx?folder=88e6cb20-fddb-4cd0-9b3f-fd

zteng,

There was no shop drawing submittal.

There also must be something wrong with the way their truss software calculates deflections for their new girder truss.

When I try a glulam beam that is same depth, 2'-4", and almost same width, 6.75" compared to 7.5", the deflection is only slightly less than theirs.

Their new girder is 33' long, 5-ply with 2x8 top and bottom chords. I would think their girder truss would deflect much more because I believe the area moment of inertia would be calculated as including only the top and bottom chords.

Is this the correct logic?

Is the right side of the truss open as they show? Can a flitch beam be made out of the truss?

No, I will hand draw a version of what the stub truss is now, give me a few minutes.

They have not suggested a flitch plate.

What they are suggesting is the absolutely cheapest repair, however bogus. They should consider themselves lucky no one was killed, and spend a little more money.

Here it is.

My new scanner is malfunctioning, I think it is leaning to the right.

• http://files.engineering.com/getfile.aspx?folder=94c6e9a2-ce6c-4f86-a5c2-68

Should I inform a supervisor at the Bldg Dept who approved all this?

Their plans checker reviewed the truss calculations w/o any red flags. I never saw them because that is the Bldg Dept's policy. The girder in question was in conflict with a note on my dwgs saying it should have had a minimum of (3)-2x8 bott. chord.

Their building inspector never red-flagged the installation of the girder. It is 33' long, with 44' span trusses attached to one side and a lesser girder truss attached to it on the other side. It was only 2-ply, 2x6 chords, and I had massive posts supproting it, and very large footings, relatively, for a one-story house.

The roof live load here is only 20 psf construction, it can be reduced to the 12 psf minimum per trib area, the roof pitch is 4:12, and the girder was unusually shallow because it was a hip roof condition located only 8' away from the parallel ext wall. The dead load is substantial - about 22.5 to 24 psf with concrete roof tile.

This piqued my interest because I remembered a project we had with a similarly long girder truss. However, I had nowhere near the supported span that you have (hell, we very rarely let the single span truss go over 40' and you have 44').

Anyway, the truss I had was also 33' long, but it supported 28' long trusses for ~10' and then one end of a continuous 40' span for the rest. The intermediate bearing on the 40' supported trusses was 28' from the girder truss, so I have significantly less load than you.

That girder was designed as 4-ply with 2x8 DF-SS bottom chords and 2x4 top chords.

Odd you were not able to review the truss package prior to submittal for permit. I am required to write a letter of review and compliance of truss packages and calculation when submitting to some review agencies. Even so, I still put the earnest on the truss manufacturer to make things right, without doing the design for them, when issues arise during/after construction.

Not to pass the buck, but my shop drawing review stamp does say, "reviewed for general design conformance." What does your shop drawing review stamp say? Let's face it, for a residential all wood framed project that we've been awarded (which means we've already undercut our peer's "how much are we willing to lose on this one, bid") we as structural and/or civil/structural engineers, would blow 10% of our design and detailing budget on a fine tooth review of a truss calculation submittal even if you had the chance. I wouldn't dream of getting too involved with the design of the trusses unless that is your specialty, and further, you're familiar with the truss design software the truss engineer/designer is using. I check lengths, pitch, drag forces, top and bottom chord loads, and girder loads, but I am still not the designer or producer of the product. You're shop drawing review stamp is not a statement that the engineer who has stamped the truss package that he and/or a technician has set up has made no mistakes. You're relying on this engineering subcontractor's specialty, hold him to it, be critical of it, but do not design it unless this is within your area of expertise (yes it's within your engineering discipline, not the same thing).

Building department plan checker/reviewer's depth of review directly proportional to work load and/or third party out sourcing. Regardless, his/her responsibility can stop at making sure you've got a professional stamp on the required submittal documents. His/her shop drawing stamp might only say, "Has a stamp on everything". In other words, it's not his/her design specialty or responsibility either. Yes as the EOR, you are forever linked to the structural performance of the structure you are in responsible charge of. When dealing with third party, subcontracted,"by owner" professional engineering and product manuf. supplier companies, as you would review his original shop drawing for design conformance, I suggest you do the same for their repair detail, and hold them, per their contract with the homeowner not you, for the "performance" of their supplied product and this repair along with it.

That said, at length, my apologies!!!!!!............provided you take a peak at this 5 panel truss print out and check loading, span, member size/species, etc., there is no user error in the retrofitted truss design input data which another professional engineered regularly engaged in the design of trusses has stamped, the hanger "and don't forget lateral ties" are properly sized, the retrofitted truss bearing panel point connection is addressed, (they may sister a parallel web member below to resolve chord/web bending moments) and all looks reasonable, wouldn't this repair detail "appear" to be in general design conformance? If installed and the performance is not within acceptable tolerances, unfortunately, they may have to make another one.

(Meanwhile, while you may be a good engineer, you'll have to ask yourself how good of a businessman you are when it comes to receiving compensation for your time effort fixing the truss designer's error. Sorry I turn this topic into a money issue, but we must defend our right to compensation for our time and effort, especially when it is required due to errors, omissions, and changes of others. I hate seeing our profession get beat up, especially when it comes to owner builder residential projects. While I studied both Architect and Engineering in college and love home design, I rarely get involved with residential projects anymore, unless designed, managed, and permitted by a registered Architect. I don't even come close to getting most home projects I bid, because I am truly realistic about the time and effort involved. Franly, I don't know how some of my peers survive. There seem to be less and less home design and construction overseen by registered Architects these days and owner builder clients rely on the structural engineers to help manage and permit their projects bleeding us dry in the process while they laugh all the way to the bank) Second apologies for the rant,....up almost all night completing my last custom home design for awhile,...while I love what I do most days,...I do need to make some money. Strictly commercial for awhile again until the right residential project comes along.

Thanks for taking the time to write down the insights. I will call you SSH for short.

What you describe is the situation in the typical consulting company as I worked for many years as an employee. I hated residential, absolutely hated it.

Then I worked for a residential only company. They knew how to do things and it became easy-going, low-stress and productive.

Now I am of an age where most others considered retirement. But I am a one-man shop working at home. I don't do any drafting, and I have virtually no overhead. I charge by the sq. ft. livable, and 2 or 3 or 4-story house cost more per sq. ft. than a one story. PT fdns are set lump fee extra, and the typical RV garage is a set fee.

In other words, I don't drive a Bugatti Veyron, but I make money on every house I do. Especially the semi-customs where we take a standard plan and tweak it a bit for the owner. I just did a semi-custom that took me a total of 1.5 hours calculation time, including printing out a set of calcs, and I billed $380. Then I got an email that afternoon, another one, same story.

I talked to the truss mfr and evidently the way they do repairs is all news to me, not like what I have seen in the past.

I cleared up some nonsense numbers and notes on their girder truss calculation sheet.

From now on, this particular mfr will submit layout and calcs to me before construction.

Same here maybe a little shy career wise,....will probably never retire however. Doing the whole package, drawings, calcs, site retaining walls, grading plans under duress, in CA seismic zones 3 and 4. Can't imagine 1.5 hours to even set up a job, let alone the 12 hours of seismic load take off, path and hold down calculations I just completed yesterday, not including respective footing design, or drilled caisson site containment/foundation walls. IF I were to work continuously, ignoring all other work, my custom home projects would take a month to two or more to complete with numerous custom details, all seismically sensitive; to complete the whole shebang, not uncommon from first point of contact, through Arch/owner changes, and permitting site grading, retaining wall and dwelling structure submittals and resubmittals for the project to easily drag out to a year or more. Owners manage to milk a lot of free consultation time out of you during that time frame, especially on the owner/builder front, not uncommon to have to set ground rules/limits, tough without offending your clients. For these once and awhile rich guy homes, have to give an approximate not to exceed fee and send monthly invoices for time and effort spent since a decent percentage of projects I've worked on are on hold and/or were never built even if design was complete. Should have been a magician like my father wanted me to be, he must be turning over in his grave right now,..."Structural Engineer,..what was he thinking!", he must be saying to himself. Have a good one. Good luck with the truss, AELLC

The truss mess is almost resolved.
I have done few big customs in SoCal.
I rarely have to talk to Owner, most communications are thru email with/ homebuilder.

My calcs are 100% on Excel, that is the big time-saver. I can take a standard set of calcs for example, the 3280 plan and modify it in 45 minutes if the owner needed an extra bedroom bumped out of the standard plan. Calcs here are so easy because wind only, no snow.

The big customs can involve some owner changes and headaches, but nothing compared to what you describe.

The truss designer may have neglected to "snap" the end of the main roof trusses (44') to the supporting girder while doing the layout on computer.

Therefore the truss software did not see any load from the 44' trusses, just a few 8' long trusses over a short length on the other side of the girder, and a small secondary girder.

"Software designers are designing more and more fool-proof programs, and the Universe is producing more fools every day.

So far, the Universe is winning"

Seems to me the software should have an audit feature - all those 44' truss reactions were not followed all the way to wall or post support ultimately, via girder trusses(s). Should have been easy to do.

JAE called it. User error. Tough to explain to homeowner when the girder fails,....."Oh, software didn't 'snap'!"

This whole discussion dredges up one of my pet peeves. When I do calculations I always try to think of the next guy. I try to make them tell a story, moving from the big stuff to the littler stuff to the details. I might not always succeed, but that's always my intent.
And then I get on occasion a wood truss submittal. They all use the same standard software. I know it's a cut throat commodity driven business, but why are the calculations so indecipherable? Small print, tough to follow, a lousy sketch, etc. It looks like they're still using a DOS based system. For pity's sake, can't they make a legible calculation with loads shown, load directions, reactions not buried in some text, stresses, utilization ratios, something that makes sense to the next guy????? Stuff that went out with HP 41C's printing out strips of heat sensitive paper for calculations.
The best I can do is to check the reactions and see if they're close to the loads denoted on the drawings. And at that, usually a phone call is required.
Open Web Steel joists are equally bad, so I now just call out the sizes I want and don't ask for calculations.

Jed,

They all use different versions of 3 or maybe 4 different softwares. Some are more legible than others.

The truss mfr that did this job has a really messy and dilapidated assembly area.

I am slowly being able to decipher the truss hieroglyphics in their calcs.

One pet peeve is the 15 CYA footnotes, include cautions and warnings to the EOR then they make no effort whatsoever to supply me with the calcs.

The repair detail wasn't so bad after all, but I caught one major omission in their calcs - there was no calculation to transfer the load of the supported trusses evenly to each of the 5 plies of the girder, and what they had was inadequate.

Plus a few very small nits and picks.

@AELLC;

I am rarely asked to do shop drawing review on residential structures.
As far as the moment of inertia, it is likely only calc'ed using the top and bottom chord areas and their separation.

For this particular client we are going to have a note on the drawings from now on - I spent all day wrangling this yesterday, starting at 4:30 AM.

They totally ignored a note saying the original girder shall be 3-ply 2x8 bottom chord minimum. I calculate this based on the type of truss hangers nailed to the bottom chord and keeping the girder bottom chord bearing stress within allowable.

I didn't use to do all that but we had a huge to-do w/ the Bldg Dept and now it is computed by Excel, so it isn't too much extra effort.

The deflection ended up being top chord and bottom chord for MoI, plus increase by 15% for shear deformation. The girder calculation by the truss mfr came out to exactly top chord and bottom chord, without the 15%.

So I suggested that they add 2 more inches to their repair girder, there was no room to do that thanks to the existing elect conduit they had to bypass. grrrr.

Quote (You don't have to design the fix...they do as a delegated engineering function. )

I ended up having to help them design their own fix... saw no other way to resolve the matter, and the house was almost finished construction - they probably were afraid the home owners would drop by for a look-see and discover something was not good, then that would have been a major fiasco.

Quote:

I ended up having to help them design their own fix...

SEND THEM A BILL.

You have every right to do so as a Professional, and should be compensated for the work you undertake.

I should send them a bill for mental anguish, $1500.

If the home owners had dropped by and seen the ceiling board pulled off, all the trusses shored, and the wall board torn off where the new posts go for the repair girder , then THEY would have mental anguish too. hehe.

Quote (So many of these pre-fab'd wood trusses are punched out by local "techs" who then send the print-outs to some PE in a far away land who seals them.)

JAE, how could that be - someone offshore has a PE stamp? How did they get it? Usually it is a local Civil Eng. PE

Quote (It isn't the software - it is the user of the software.)

The explanation I got from "anonymous" - the tech draws the truss layout, very similar to ACAD. He neglects to "snap" the end of the 44' common trusses @ 24" oc to the girder - maybe they were 2" off, but looked connected on his computer monitor.

Now the truss calculation software "had no idea" of all that load on the girder. Now supposed he was careless, hung over, lack of sleep - he didn't notice anything unusual.

Another software success story.

@somewhatofanerd- LOL. I HATE using other people's software... Black box of other people's work for which you are responsible anyone?

"Far away land" doesn't necessarily mean off-shore; often in CA for a job in NC, but the have the required stamp.

Yes you would think that a huge expensive truss design software would have a load and reaction auditing, self-check feature.

I was being a bit melodramatic with "far away land". Some states in the US are simply La La Land to me.

A few years ago, I had to disapprove a cold-formed steel truss submittal 4 times before they gave me trusses that met all of the design criteria.

I thought this repair was a done deal last Saturday.

Yesterday, I kept getting calls from the truss mfr. Still not done. At least, they are now offering to pay me for my time, so now they are my new best buddies.

The funny thing is that you never talk to an actual engineer at the truss companies. Just their "Designers" and other job titles that get thrown around. To have some fun call the truss company and ask to speak to whomever's seal is on the job. Good luck with that.

There are no engineers at the actual facility, and the guy /ga who stamps the calcs is usually doing that for more than one truss mfr. Yup.

When I ask, they always give me the contact info for the satellite engineer. When contacted, the engineer seem sto be more than happy to help.