Any tips / sources for warehouse design / bid?

[AaronMcD]

We are asked to bid 140k sqft of warehouse space, 2 buildings, 2 stories each. Normally do residential and hospitality. Any tips on how to bid, and online sources or personal tips for design? (seismic area)

Anyone have special design considerations that might not be intuitive? Mainly things like how to deal with the huge diaphragm (e.g. do you break it into subdiaphragms? Is there a length limit between lines of seismic resistance?) or foundation (foundation ties? cross footings or in-slab ties? Loads to design ties for?).

Our usual projects do not have much optimization. Where would you consider going over minimum sizes? Any typical construction methods and/or details?

Any typical construction methods that may not be obvious? All steel, vs concrete or tilt up first floor? Hot roll vs OWSJ at roof? (interior columns, 30 ft spans)

Kind of a broad open-ended question, I know. I can probably find all the info on design eventually, but any head start is appreciated. First step is bid.

http://www.hellodwell.design

 

[AaronMcD]

Good point about factored loads. I doubt a warehouse sees 32 psf roof live load.

So with PEMBs, do they just angle the purlins to match the slope and design for the out of plane loading?

http://www.hellodwell.design

 

[canwesteng]

Shouldn't you check that it remains elastic under SLS loading? S16 is explicit for that when designing beams with different sized flanges. In elastic design, for symmetric wide flange sections, the load factors essentially make sure that it is impossible to yield under SLS conditions so no need to check.

 

[phamENG]

Pretty much. It can be done with joists, too, but there's plenty of detailing to be done and I understand erection is a nightmare trying to keep them from rolling over. So the labor costs shoot up when you try that (I almost did once when I was a new EIT...my boss made sure I knew not to draw it like that again...)

 

[dik]

pham... I have no idea of why it's not used more. I'm a strong advocate of the use of it, but have never pushed it on engineers I've worked with. On the big project above... I picked it up, quite by accident. I dropped into NORR to see if the architect that worked on the Cornwall centre was back from Nepal. He was the architect on the Tribhuvan Airport in Kathmandu. He was expected back in a couple of months, but the engineering manager asked if I wanted to do a project for them... yup was a 40' clear height... The dept manager was the only one at the firm that could seal... so, had to teach him plastic design. After the project was complete, I had nearly 1000 budget hours left over, and the steel quantity was more than 4 psf less than what they had esimated. I don't think the engineering manager used plastic design beyond that project.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

The only restriction that occasionally pops up is that the section has to be a Class 1... and sections can vary between Class 1 and Class 2 depending on the yield strength. In the last several years I only consider 350MPa for yield since most rolled steel is that anyway.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

With PEMBs they try to develop a shape that matches the elastic moment diagram. If it exactly matches, then the entire structure goes plastic on overload... no redistribution.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

dik - Inertia. It seems the majority of engineers in the States are still using ASD, and many of them aren't even aware that it's not Allowable Stress Design anymore. The slight of hand that AISC pulled when they combined the ASD and LRFD specs is the only reason they use any kind of strength design at all.

 

[AaronMcD]

Concrete is only LRFD.
Wood is all ASD.
Steel was LRFD when I learned it in college maybe 15 years ago. All the older guys still like ASD. I don't know what the big deal is. The procedure is almost the same anyway.

http://www.hellodwell.design

 

[dik]

I remember using graphic solutions for plastic design, and Arnold Crosier showing me how to do a 'straight edge' parabola... good old days.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Back in '65, we never took ASD other than for historic purposes. It was all Ultimate Strength Design (Limit States). We were the first year that did limit states...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

Aaron - I'd say concrete only evolved from working stress to LRFD because ACI changed the code and phased working stress out. If they were side by side I'd be willing to bet most would still use working stress. A prime example is wood. There's certainly LRFD wood design in the NDS, but nearly everyone ignores it in favor of ASD (me included!).

I was taught LRFD in school but I got to my first job in building design, designed a small building using LRFD, and my boss said "What is this!? I can't check this...do it again the right way!" (He was referring to ASD...)

 

[mtu1972]

My school was behind those referenced above. Took my first design classes in 1971. Steel was Allowable Stress Design and concrete was both Working Stress and LRFD as the Professor stated that they weren’t sure LRFD would be used by everyone.

First job, the boss did the concrete with WS to compare with my LRFD results. He was OK with my results and let me continue doing concrete design that way.

When steel went to USD, I did make the switch, but it always ticked me off that we then had different sets of Load Factors. At least that has now been resolved.

My career has been primarily in the upper Midwest (MI, MN, and WI) and our soil capacities were typically Allowable bearing pressures, so we have to calculate the loads to the foundations in ASD.

gjc

 

[dik]

If you get used to it... you can have the DL and LL and easily convert to working stress.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

Steel was LRFD when I learned it in college maybe 15 years ago. All the older guys still like ASD. I don't know what the big deal is. The procedure is almost the same anyway.

I'm 58 and I suppose considered an old guy.
I use ASD for steel simply as a way to save time. Gotta use service loads anyway to check deflection so might as well use them for the demand as well. I typically only do small structures so the material savings are not significant and serviceability seems to control most of my designs.