Sagging prefab wood Girder Truss on custom home under construction 3

[AELLC]

I am the EOR for said house. When the concrete roof tile was stacked on, a girder sagged badly, probably big mistake by truss co.

They sent me a repair method for my approval, but to me it looks bogus. This just happened late today, and I will study it more closely tomorrow.

My question- who is responsible for what here?

 

[AELLC]

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.

 

[AELLC]

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.

 

[structuralsteelhead]

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

 

[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.

 

[AELLC]

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.

 

[structuralsteelhead]

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

 

[JedClampett]

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.

 

[AELLC]

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.

 

[AELLC]

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.

 

[XR250]

@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.

 

[AELLC]

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.

 

[AELLC]

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.

 

[CELinOttawa]

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.

 

[AELLC]

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

 

[AELLC]

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.

 

[AELLC]

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


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.

 

[somewhatofanerd]

Another software success story.

 

[CELinOttawa]

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

 

[SLTA]

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

 

[AELLC]

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