Is the AISC STEEL CONSTRUCTION MANUAL as complicated as it looks? 4

[curiousmechanical]

Hello,

I am a mechanical engineer. I have been designing industrial equipment for the past eight years. I am somewhat of a reference book junky and I recently purchased the AISC STEEL CONSTRUCTION MANUAL (14th Edition). This book seems very useful, but it also seems like it might be over my head. On occasion, I need to design service platforms for our equipment. I thought this book might help me do a better job.

So here’s my question:

Is this book something that a mechanical engineer should be able to use; with a reasonable learning curve? Or, is this book very specialized and only useful to hardcore structural engineers? Right now, I am completely clueless. I don’t know anything about LRFD, ASD, etc. Also, I am worried this book will require the reference of other AISC standards. I don’t have an AISC membership and I don’t plan to buy any more structural reference books. If this book isn’t as complicated as it looks, does anyone have any advice on how to get up to speed quickly (i.e. how to learn the basic concepts, so I can take advantage of the various tables and formulas)?

Thank you for your help everyone!

 

[JedClampett]

It's very complicated to apply the specification direct from scratch. I've been doing steel design for 35 years and the code seems to have added a lot of new slenderness and other checks. Most of us use the tables, charts or other design tools as much as we can. These have accounted for almost all the oddball rules.
ASD is Allowable Stress Design (loads without load factors) and LRFD is Load Resistance Factor Design (loads with factors depending on their predictability and likelihood). They had to include both methods to get the old hardheads (like me) to use the "new" "improved" specification.
But I would be hesitant to cut you loose to use the tables. You need ASCE 7-10 to get the load factors and combinations. And interpreting bracing and fixities can be tricky. Even beam length can be misinterpreted. It's not of matter of other AISC Standards (thank god, they're all pretty much included, except seismic), but the nuances.
It's gotten more complicated, but luckily I've grown up with it.

 

[SteelPE]

Coming from scratch I can see how it would be a daunting task starting from scratch but once you get used to it, it's really not that bad.

If you are designing platforms now what code are you using? If you are in the US and you are using steel I would hope it would be the AISC.

As JedClampett points out, most designers use tables and charts located within the book or simple spreadsheets that were created using the specification. The specification is only about 200 pages or so w/o the commentary. Most of the other pages in the book are tables and charts that were derived from the specification. Most people warn about using the tables and charts w/o knowing how to calculate the values within the charts.

If you need to use the book on a regular basis to do you work, I would suggest looking into a steel design class at a local university. There they will show you the basics of designing steel members which would make using the book that much easier.

 

[cliff234]

In lieu of taking a class in steel design, you might want to purchase a good book on structural steel design. I found several on Amazon. Make sure the book you buy is written for AISC 360-10 (the latest steel specification - the one that is in the 14th Edition Manual that you purchased). Perhaps someone can give you a specific recommendation. Structural Steel Design (5th Edition)by McCormac & Csernak looks pretty good. The four general topics that you need to learn about are, beams, columns, stability and connections. (There are other steel design topics, but those are the primary ones.)

 

[Jerehmy]

Steel Structures - Design and Behaviour by Salmon is a good book. I saw it online in a bunch of places for <50$. I have the fifth edition but I'm sure a 4th edition wouldn't be much different and a lot cheaper.

 

[JedClampett]

It's funny that you ask. I'm currently in the middle of the AISC Webinar called "Basic Steel Design - A Review of the Principles of Steel Design According to ANSI/AISC 360-10." It's eight 1 1/2 hour sessions. I can't imagine someone without a pretty sophisticated knowledge of the code sitting through this course. And this is just a refresher to bring the new aspects of the code to light.
Anyone else out there taking this course? In general I like it, but the sessions tend to get rushed, especially at the end of each one.

 

[curiousmechanical]

Thanks for the helpful responses guys!

It sounds like this is more demanding than “Machinery’s Handbook,” for example. As suggested, I will pick up an introductory structural steel design book. Unfortunately, this is a very small part of what my company does, so I doubt they would ever send me to classes.

Just so you know where I’m coming from, let me further clarify my situation. We are small OEM. Our equipment is very large and requires service platforms. Most of the time, we only create a platform layout and have an outside vendor do the detailed design and manufacturing work. However, these vendors are usually overseas (i.e. low cost) and I doubt they are familiar with AISC codes. They barely seem familiar with OSHA standards. In any event, the final product does pass the smell test (members look too heavy if anything), so we seem to leave it at that. I don’t really agree with this system, but I am low in the hierarchy and it is the way our company chooses to do things.

We have a small engineering department and we design equipment that requires a wide range of engineering skills. It’s a tough environment to work in because you never feel like you know what you are doing, but you have to find ways to make decisions and move on. I sense this is common at small companies.

In any event, my goal is to gain some basic structural design skills. Partially for personal development and partially to help me create more accurate platform layouts and help me better evaluate our vendor’s designs. Also, I have seen us take on large support structures in the past. These somewhat blur the line between mechanical and structural engineering. I believe these were analyzed with basic stress formulas and FEA (i.e. no AISC codes). Therefore, I thought some basic structural knowledge would be useful in case I get a similar project in the future.

Thanks again for discussing this topic with me.

 

[fegenbush]

I recommend Structural Steel Design (either ASD or LRFD) by McCormac. You can get used copies of past editions for about $2 on Amazon.com. The code references in them are not current, but you can get the introduction to the material that you are seeking for a competitive price and McCormac is very easy to read.

 

[DCBII]

I work in a firm that has both structural engineers and mechanical engineers. Occasionally a mechanical engineer tries to do my job and I cringe when I see their designs, mainly for the following reasons:

1- They seem to think almost everything is a moment connection.
2- They completely ignore the stability provisions in the code.
3- They don't know how to properly apply load combinations.
4- They don't use industry standard connections.
5- They don't consider vertical AND lateral load paths.
6- They are unaware of ASCE 7's existence.

A manual might help you with a few of these items, but it's not a substitute for experience. If you want to design anything structural, a good place to test your "basic" ability is on the Civil/Structural PE exam. If you can pass that, you're might be competent. If not, you shouldn't practice structural engineering at all. It's outside your area of expertise.

I've been out of college and in the field now for 7 years, designing steel the whole time (working under several experienced SE's). I took several advanced steel design courses as part of my master's degree. I wouldn't dare say I had a "basic" understanding of steel design until about 3 years ago.

 

[SLTA]

This might be a start:

http://www.learnerstv.com/Free-engineering-Video-lectures-ltv323-Page1.htm

 

[steellion]

I agree with DCBII. There is way too much to consider and way too much at risk for a non-structural engineer to design even a basic system like a platform or a catwalk. I mean, I could probably fake my way through ASHRAE by applying the formulas in the manual, but the end result would likely be something that a practicing mechanical engineer would find to be non-standard and all wrong.

 

[curiousmechanical]

Thank you for the additional responses.

I appreciate the reality check from you guys. I kind of sensed that mechanical engineers have no business designing platforms. Unfortunately, management thinks we should be able to design anything mechanical. Regardless, I’ll be sure to avoid overextending myself on future projects (even if that involves speaking up). Proper structural engineering is clearly over my head. I should have figured as much. After all, structural engineering is its own separate field.

 

[a2mfk]

Unfortunately, management thinks we should be able to design anything mechanical.

And maybe you can- mechanical that is. But I don't consider most structures to be mechanical. If my stuff is moving, I am in trouble!

The value of a modern engineer is in our high degree of specialization. How complicated could machines and structures and electrical systems be if we (engineers) all tried to do it all? Not very I figure. I call myself a structural engineer but there are numerous materials and systems that I am unfamiliar with, many things I would not be comfortable designing. Nothing to be ashamed of, we just all have our own specialties and experiences. It's the old "Jack of all trades, master of none" saying....

I would suggest finding a local structural engineer to work with when you need, one who is proficient in steel design. I have done quite a bit of this type of work for steel fabricators including equipment supports and platforms, and the fabricators don't assume any unnecessary liability and they don't have the volume for a full time SE. When some tricky aspect comes up in regards to building design or attachment, we can handle it since we have a full range of building and specialty structure design experience.

 

[Bagman2524]

I started with the 8th edition (red book). The ninth edition (green book & my favorite) didn't change a lot of the technical stuff from the 8th edition but improved the format. Like JedClampett, Never really used LRFD much when it came out and still don't like it. The 13th edition, which combined LRFD and ASD has added a lot to the technical content. IMO, mostly an effort to trim down design. In some cases it may be worth the extra engineering involved, but in some cases not. I'd prefer to the option to still use the old 9th editin.

 

[msquared48]

To me, more complicated (LRFD) just means more room for mistakes and a need for insurance. I just use ASD too.

Mike McCann
MMC Engineering

 

[AELLC]

I had been designing with steel since 1974 (back in ASD days). I adopted to LRFD but have always used ASD on occasion, and now I use ASD exclusively because I design mostly wood structures and want to keep my ASD load tallies consistent if I need an occasional steel beam or post.

I have always heard in seminars where LRFD steel design that the LRFD method for steel beams was "calibrated" to result in the same result of beam size as when using ASD (for most commonly used ratios of dead load to live load), HOWEVER the LRFD method results in much shallower and moderately lighter beam sizes, and still be safe...however deflections have to be checked carefully. Also, using LRFD results in slightly smaller column sizes.

It has always been an assumption of mine that LRFD is advantageous in designing large structures, to result in a moderate amount of cost savings due to less total tonnage of steel, and to compete with concrete because concrete design changed much earlier on to the ultimate strength (factored loads) in the 1971 ACI.

However, for designing an occasional service platform, I don't see any inherent advantage to use LRFD; and many handy Excel design spreadsheets offered free on the AISC website are in ASD.

 

[AELLC]

Sorry, I should have checked my previous post


HOWEVER the LRFD method [highlight #FFFFFF]for composite beams[/highlight] [highlight #FFFFFF][/highlight]results in much shallower and moderately lighter beam sizes

 

[msquared48]

So that means there is less additional capacity for future additions too, emparting more expense for any future changes.

Mike McCann
MMC Engineering

 

[AELLC]

Well, it depends on the situation - if you are in a company that specializes in large structure and you are competing against another firm that proposes to design the same structure in concrete, you definitely would use LRFD in your steel design.

On the other hand, I did a large governmental steel structure back in ASD days and there was no competition - we used 100 psf live everywhere to be safe if there was a remodel of a floor and there were a lot of paper storage files, etc.

Otherwise we would have used the 50 psf "office" live plus 15 psf partition.

 

[XR250]

Just about everything I design is governed by serviceability requirements - ASD all the way.