Beam End Reaction Table 1

[jseng9]

How do engineers create a beam end reaction table that provides a design load (LRFD) for each beam depth: W12, W14, W16, etc.?

Would like to create one of these. My firm only uses the AISC tables but I think this is conservative.

Thanks!

 

[r13]

I've never done that before, but I think the beam capacity can be established filter through 2 criteria - end connection and deflection.

 

[phamENG]

By using the AISC tables I'm guessing you mean 50% of the UDL for the beam span? Yes, that is usually overly conservative though it can be shown to be very unconservative under abnormal loading that isn't uniform.

The best way to do it - design the building and figure out your reactions. Then use those reactions in your table. Assigning the same load to all beams of the same depth may make sense for some projects, but not always. If you have a W18x35 in one place and a W18x234 in another, do you really want to try to get the W18x35 connection to be able to resist the same thing as the W18x234? This is obviously an extreme example, but it's applicable to smaller differences, too. Besides, using the actual reactions can result in a cost savings for the owner. There are exceptions - buildings that are likely to be modified in the future (roofs of shopping centers, for instance) where maxing out connection capacity makes sense. But I think those are the exception and not the rule.

Setting up those standard tables is good for business - they speed up document production and you can get more jobs done faster. But sometimes you need to take a closer look and make sure your "typical" detail/table/schedule really makes sense for the specific and unique project on your desk.

 

[dik]

Something like the attached?

Check it before you use it...


Dik

 

[jseng9]

Something like the attached

Yes exactly. Just not sure how you created that. And it makes sense that all tables need to be checked.

 

[dik]

Just use a vlookup to a sorted AISC section property table... and a list to the section 'names'. The logic is on the sheet. Have upgraded it to accommodate other section shapes... see earlier questions in the E-T spreadsheet forum... got some useful help from others.

Dik

 

[BAretired]

When I remembered to do it, I put the reaction on the framing plan. Often I didn't bother because the dead and live loads were specified in a general note. Unusual connections, when present, were usually detailed on the drawings. When detailing was to be by the fabricator, forces were shown.

BA

 

[dik]

BART: Pretty much the same here.

Dik

 

[r13]

I think the OP wants to make a table, the same as AISC provided, typical to all projects that using those beam sections in a simply supported situation. It will be time consuming to construct the table, but could be worthwhile for the long run, if dealing the same type of projects with the same range of beam sections.

 

[271828]

I'd recommend doing it specifically for each project. Go through your beam designs and find the maximum reaction for all of the non-huge W16 beams and put that in the table. Same with the other depths. Indicate that the table applies unless noted otherwise, and put weird large reactions on the plans.

Sorry for the following two paragraphs, because nobody likes unsolicited advice, but I can't help myself.

As an EOR, I designed quite a few steel-framed buildings with complicated framing and fast-track schedules. With zero exceptions, we put the reactions on the plans. Adding the reactions was so little effort that it didn't register as a part of the work flow. I can get "W16x26 R=30 kips" on the drawings about as fast as I can get "W16x26" on there. The difference in required time is literally a few seconds.

I've been doing delegated design of connections for a while now, and we spend a ridiculously large percentage of the time sorting out problems caused when the EOR did not provide all reactions, and instead said to design for half the maximum total uniform load. (OP, I realize this isn't what you're asking about.) I wish there was an effective way to plead with the EOR community to stop doing this. AISC has been trying for years, so presumably there isn't one.

 

[dik]

That's what my spreadsheet does... and you can cut and paste for Beam B01 to Beam whatever... the front end data is done by variable, so cut and paste works. Too many beams and too many spans for an easy table... I've used this sheet for years...
Dik

 

[BAretired]

I agree with 271828 up to a point. Do it for each project but put actual reactions on plan, consistent with design loads, not weird large reactions. That is just as bad as specifying that all connections be designed for half the maximum uniform load.

I see no merit in using a table, better to specify the beam size and reactions at the plan location where they occur. There could be a few exceptions which would be more readily found on plan than a schedule.

BA

 

[human909]

Forgive my ignorance but what is a beam end reaction table?

Also does it have much of a role for those who use structural software to do most of the calculations anyway?

 

[271828]

I see no merit in using a table, better to specify the beam size and reactions at the plan location where they occur. There could be a few exceptions which would be more readily found on plan than a schedule.

I should've been clearer. This is what I think also. IF he insisted on a table, then I'd recommend doing it as in my first paragraph.

Another thought regarding the use of tables. Years ago, I was designing an addition and was extensively referring to a set of existing drawings that didn't indicate any sizes on the plan. All composite beams were B1, B2, B3, and so on, and there was a schedule in the section sheets. This was awful. If I see a 30 ft beam with "W16x26 (30 studs) R = 30 kips" I have a pretty good idea whether that makes sense or not. If I see B27, I have no clue. This speaks to the superiority of having the information right there on a beam.

On my last connection design job, the EOR used the maximum total uniform load approach. I found three beams that had reactions landing close to the support. Quick calcs indicated the reaction was probably higher than half the MTUL. I sent an RFI and the reactions were quite a bit higher than half the MTUL. If the EOR was looking at the beam and writing reactions on the plan, he would've caught this. Instead, he was relying on the MTUL to save him.

 

[BAretired]

That's what my spreadsheet does... and you can cut and paste for Beam B01 to Beam whatever... the front end data is done by variable, so cut and paste works. Too many beams and too many spans for an easy table... I've used this sheet for years...

Why is it necessary or desirable to put all that information on a drawing? The fabricator needs to know only two things, namely that B01 is W6x9 with a maximum reaction of 6.3 kips. Any of the other properties he can look up in his handbook. Is there some reason why the beam specified in Imperial has span defined in Metric and vice versa?

I think that is just cluttering the drawing up with a lot of unnecessary information which is needed by nobody. And if revisions come up, as they always do, you have to go through the whole bloody table to correct it. I prefer simplicity.

BA

 

[dik]

BART... the only information that goes on the drawing is the reaction. The rest of the info is for my info... or if I'm checking someone else's information. The yellow 'boxes' are the only input data... the rest is 'free'. I've had some projects where I may have 30 beams on the same sheet... and print it off as a *.pdf file that goes into the folder.


Dik

 

[BAretired]

Ah, sorry dik, I thought it all went on the drawing.

BA

 

[dik]

Not a problem...

Dik