Long steel beam for residential deck standard practice 3

[DoubleStud]

What is the standard practice if I have a series of straight steel beam (5 columns, 4 spans) that is 50 ft total? This will be supporting a high end concrete deck with heating tube. Do I design the beams as continuous and put a connection at the inflection point? Do I design the beam as single spans and put a connection somewhere just next to the middle column? Other way? This steel beam will be visible. I don't think they want a 50 ft long beam. Typically the decks I design are not this long. If I use steel, typically I have been specifying continuous beam. Maybe I just specify the steel beams to connect to the side of the steel columns? That way I have 4 short pieces? What would you do?

 

[BridgeSmith]

You can design it as continuous, with hinges at the inflection points, or as simple spans, but it needs to be detailed and built consistent with the design. The slab obviously needs to be continuous, so I wouldn't consider any option other than continuous beams. It's still good (and for bridges standard) practice to put the splices near inflection points.

Bridge girders require splices to carry the full moment capacity of the girder, but the Live/Dead load ratios are typically fairly high, where yours probably are not, so using a web splice only may be adequate for your design.

 

[gte447f]

I prefer to design and detail as 4 separate simple spans.

 

[XR250]

Depends if they were planning on using a crane or not.
I usually ask the contractor what their preference is and can they get a 50 ft. chunk of steel on site.

 

[DoubleStud]

If 4 separate beams, how do you detail at mid columns?

 

[driftLimiter]

Column frames to top of beam and then shear tabs from beam web to column.

 

[gte447f]

For simple spans I like standard single plate shear connections.

 

[BridgeSmith]

If you design and detail it as simple spans, watch the end rotations of the beams over the interior columns to be sure the deck isn't going to crack there.

 

[Tomfh]

For a typical deck, simple spans with simple connections to the columns. For a high end deck, whatever you want.

 

[gte447f]

To BridgeSmith's point, design for deflection control and crack control in the slab are important considerations, but I don't think either necessarily rules out simply supported beam spans.

 

[RPGs]

Obviously, there are many ways to skin this cat. It appears one of your major concerns are the aesthetics since it's exposed and very high-end. On projects I've done, aesthetics are the be-all-end-all design requirement, largely irrespective of cost/complexity. Perhaps some inquiries to the architect/owner will rule out some of the options for you.

 

[StrEng007]

DoubleStud,
Do you have a sketch to go along with your OP?

 

[DoubleStud]

Here is the detail per architect. The beam will probably be steel. There is an existing drip through deck. It will now be waterproof with concrete topping.

 

[RWW0002]

I have to say, I have not seen many concrete-over-wood decks (a few but not many), and even fewer concrete over wood supported by steel. I am not sure what your joist spans are or exactly the dead load of the proposed system, but hanging that much dead load off a ledger may be difficult to make work. Existing framing below should be checked for the new dead load. I think I would be very tempted to make this a "free standing" deck if possible.

Regarding the steel beam, I agree with the comments above. Continuous or simple span will not make a huge difference as long as it is detailed accordingly and constructability is considered based on the size of the overall job.

 

[Eng16080]

My default would be 4 simply supported beams with shear tab connections to the columns. It’s simple and easy to install. If I understand correctly that the beams only span 12.5 ft, it should be easy to choose a size which has negligible deflection and end rotation.

 

[XR250]

Yea, hopefully you have a better connection to the house than is what is shown.

 

[DoubleStud]

The new ledger will be lower and wont line up with rim. So I have to put flat 2x member between studs to accept however many ledgerloks screws (or anything similar). The 2x members will be attached to studs either side with simpson angles, or maybe ill install studs below the flat 2x both sides. That’s my plan, let me know what you think.

 

[DoubleStud]

Like RPGs pointed out, aesthetic is my #1 priority. I have never seen decks in this area with steel beams hanging from the side of columns. They usually go above the columns. I am thinking about maybe just size the beam for simple supported and just connect the web about 6” from the column (no moment transfer). I feel like connecting it at the inflection point doesn’t look very pretty? Better to be closer to the post?

 

[gte447f]

Doublestud, refer to AISC manual Part 10 for beam-to-column, standard single plate shear connections.

 

[gte447f]

Frankly, I don't see the need for steel beam(s) if all the other framing is conventional wood deck framing. Also, like RWW0002 said, the combination of the various materials shown in the drawing is something I also have not seen often/ever. I would not be keen to combine concrete and wood. That said, the steel beam(s) portion looks pretty straight forward.

As an aside, the reason you more often see beams continuous over columns in residential construction, including decks, in my opinion, is because residential contractors/deck builders/landscapers are simply not very knowledgeable or experienced with typical/standard structural steel construction.