Built up section question

[7202cdz]

I will design a simple support beam to support linear load. In stock W24x84 beam will be used. The moment and deflection are overstressed (limit). The beam shear capacity is adequate. I will add double angles to form a built up section like truss in order to increase section modulus and section moment inertia (space under beam is ok and this is our prefer option). I am wondering how to design the web members. Is it same as standard truss and the web members shall take all the shear force?
Please see attached sketch and please someone provide me help on this issue. Thanks

 

[BAretired]

A more efficient way to increase the flexural capacity of the W24x84 is to add a steel plate to both top and bottom flange. In that way, you would still be fully utilizing the strength of the stocked beam. Of course, if the beam is too shallow for the span, you should use a deeper section, perhaps a truss. If you use a truss, forget about using the beam as a top chord.

BA

 

[dhengr]

7202cdz:
And, you still resist giving us some of the particulars on the problem, like span length, total depth of the truss, and actual loadings. These would be easy to show on your sketch. Is this new construction or is the W24 in place already, and now, to be reinforced. If your sketch is in proper proportion, the span is about 80', the truss is about 5' deep, and the panel points are about 5' o/c, why not show this. You would be surprised at how important that type of info. is for an experienced engineer who is asked to comment on your problem. They need that info. to make judgements about the feasability of the concept, and what might control its design, etc. They look at your sketch and wonder how you are going connect the verts. and diags. to the bot. flg. of the W24, they sure can’t go through it as your sketch shows, although I suppose your thought process probably was that you wanted their work point to be at the center of the W24.

If you have really read the responses for their full meaning, I’m a bit surprised that you haven’t picked up on the fact that most of the experienced engineers here think your approach to the problem is a little bit crazy, not impossible. A very inefficient use of material and overly complicated for what we think you are trying to do. Another useful piece of info. would be why you are forced to use the W24 for the top chord. Our initial reaction is that that is a difficult way to handle a simple problem. Probably the best way to use the W24, would be to split it, as someone suggested and use the WT’s as top and bot. chords for a truss you design and fit-up the normal way. Although, the W24 may not yield the best sized WT’s.

 

[paddingtongreen]

I think the OP is constrained to use material on hand, I've been there, it's not a good place to be.

dhengr, the transition from material to labor being the more expensive part of the cost had started in the early fifties when I started working. To be honest, I think there is more than a touch of culture involved. The USA goes big, unnecessarily in some cases where the UK the culture is less bombastic (I don't mean bombastic unkindly, I just can't come up with a better word). I did start out with a mix of work on refinery design, drawing from small access platforms to 1000 ton cat cracker structures, I enjoyed those, they were riveted girders, very pretty.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin