drag strut connector added below existing roof deck

[ps31]

I need to add a drag strut connector to an existing beam perpendicular to existing steel roof joists at an interior condition below existing decking. The question is how to fit the drag strut connector below the deck and weld it with out removing the deck. Ideas are a flexible shape like a Z shape or an angle welded to the flange of the beam.

 

[a2mfk]

Though its pretty clear, a sketch always helps.

Are you trying to drag the shear from the beam into another element, or from the deck into the drag strut?

 

[ps31]

From the deck into the drag strut. The building suffered a partial roof collapse (100ft x 100ft for a 300 x 300 foot square building). The remaining building is L shaped. The challenge is to take what was an interior wall and make it a shear wall. I have added wind bracing cables to the columns. Now I need to drag the shear from the deck to the beams at the newly braced frame without removing the existing deck.

 

[dhengr]

Ps31:
Cables are very elastic due to their shape and manuf’r. make-up, they stretch a lot when loaded, they may not make the best wind bracing elements btwn. columns. 1" round bars with turnbuckles might be better. Without roof framing plans, showing beams, joists and where your are taking the load from and to you leave us to guess what will work. I wouldn’t use an unsymmetrical shape for whatever complications that implies. Since it runs perpendicular to the joist, it can be spiced, and any length you can thread through the joists. Hang it from the joists, for support of self weight, and below their top chords and to miss the diagonal webs. The trick is the connection to the beam when the strut is a few inches below the bm. flg., and that eccentricity.

Alternatively, since you force us to guess.... I would convert the deck loads to shear flows at the beam, drill a hole in the deck, hang a funnel under said hole, with a garden hose to the bottom of the funnel; then you can take shear anyplace you wish without worrying about the surrounding structural elements interfering.

 

[BAretired]

Provide a sketch, please.

BA

 

[DaveAtkins]

First, I suggest you check the existing joist seats--can they transfer the diaphragm force to the beam through the seats? Joist seats do have rollover capacity.

DaveAtkins

 

[trainguy]

ps31,

You probably know this, but you're going to have to check the beam's connections for the "new" axial forces it now has to transmit into the bracing system.

Also, whenever I've designed diaphragms and bracing systems, we used to provide a full length connections of the deck into the support structure without counting on joist seat rollover capacity.

dh - can you clarify about funnels and garden hoses?

tg

 

[a2mfk]

I think its a super nerdy shear flow joke? I like it!

If only it were that easy, like plumbing.

 

[BAretired]

What's to clarify? The shear flows down the funnel into the hose and can be directed anywhere, right dhengr?

BA

 

[dhengr]

BA... Exactly, and ‘ Nuff said. This may be my shortest post ever.

 

[trainguy]

dh, ba,

But doesn't that depend on the viscosity of the shear...?

That joke was shear genius...

tg

 

[dhengr]

TG:
I think you mean sheer, not shear, but I’ll accept the genius part... thank you, thank you, I can’t get my hat on anymore. This was going to be my second shortest post ever, then I got carried away....

As is usual, the OP’ers. often don’t give enough info. to really address the problem; sketches, viscosities, etc., maybe my solution wouldn’t work in real cold climates, although you could put an electric heat blanket on the roof to adjust the viscosity, and if done correctly, and in the right pattern, that in itself might control the shear flow in the direction you actually wanted it to go, and save the need for a long hose. BA understood immediately, because over the years we have both been asked to fix someone else’s shot bulls on a structure, and sometimes you have to be very creative to do that.

Then, you introduce viscosity, and now you’re getting super technical, actually, the shear flow I was talking about is measured in lbs./inch, still it usually flows, whereas you are now talking about poises, stokes or Saybolt seconds and the conversion btwn. the two systems is damn near as difficult for us structural engineers, as mass and weight in dynamics problems, and the slug and N and kg’s and all that stuff, and consistent units. Maybe you should stick with trains; if you stay away from hydraulic snubbers and draft gears, viscosity doesn’t really come into play. Although some of my railcars had both of these and intentional hydraulic systems, for lifting and shifting, as part of the car design.

In a slightly different vein, I would really like to be able to communicate with some of you outside this forum, directly by e-mail or phone. I understand that the people-who-be at this forum frown on e-mails, etc. in posts, and I understand their reasons. But, is there any way, through a third party web site or some such, that you could transmit your e-mail or phone number without it showing up here. I think I actually gave you my e-mail in an earlier post, but you never revisited that thread. I can talk a hell of a lot faster than I can type, and we can ask questions in mid-sentence instead of three days later, when we don’t understand something you are saying. I once asked about private messaging btwn. members and they said they tried that once and didn’t like the results. After all, we take a chance every time we click on an attachment or an e-mail we don’t recognize.