Lateral load resistance of slab on metal deck
Lateral load resistance of slab on metal deck
(OP)
I am involved in the design of a 5" total depth concrete slab on 1 1/2" metal decking. I am designing the slab on deck and someone else is desiging the steel framing. My questions are regarding the lateral load resistance of the floor. The floor is being designed for 10% of the DL of the floor system. If the 5" total depth of concrete (although only 3.5 inches will be effective in resisting shear) can resist the end shear due to the lateral loads, do the deck connections (fastener pattern and sidelap screws) to the steel need to be designed for this same load? I'm unsure if the shear will actually be transferred to the deck since it's being used a form deck during construction. I spoke to the person designing the steel framing, and he also designed for this lateral load, providing continuous bracing around the perimeter to take out the lateral loads. I was always under the impression that the concrete (if designed to do so, which it most likely could since it's rigid) resists the lateral load and the steel is designed from gravity load and no bracing would be required. What I'm understanding here is that he expects the lateral load to be transferred from the concrete to the deck and from the deck to the steel through the puddle welds in the 36/7 pattern I designed. Is this really the case? I didn't think so. I never thought the steel saw that much of the lateral load.
Another issue is the bracing of the top flange again LTB. If the connection between the metal deck and steel framing is based on the lateral shear capacity, and not the unbraced lengths of the beam, how do you know how much lateral force is required to prevent the beam from LTB? I know of Appendix 6 is the 13th ed. of AISC. Is the criteria you would use?
Another issue is the bracing of the top flange again LTB. If the connection between the metal deck and steel framing is based on the lateral shear capacity, and not the unbraced lengths of the beam, how do you know how much lateral force is required to prevent the beam from LTB? I know of Appendix 6 is the 13th ed. of AISC. Is the criteria you would use?






RE: Lateral load resistance of slab on metal deck
RE: Lateral load resistance of slab on metal deck
Mike McCann
MMC Engineering
RE: Lateral load resistance of slab on metal deck
RE: Lateral load resistance of slab on metal deck
into braced bays? There are some issues here with this floor. The design is for a new floor in a power
plant. They are not wanting to use the typical method of puddle welds to attach the deck to the steel because they do not have a process to do so. The power plant industry is much more stringent on this type of thing so I have to go along with it. I am also hesitant to use TEK screws as I need a 36/7 pattern and dont want to drill so many holes through the beams and girders. My boss has suggested using headed studs in a non-composite manner. The steel
framing is already designed and there is not enough time nor funds to redesign it due to the schedule of the
project. One issue with adding headed studs would be that the slab and beams would act at least partially
compsitely since studs are installed, right? Also, some general questions: if the slab is non-composite, how is the shear transferred from the concrete to the deck, friction? What capacity would I use for the shear studs? Could I just calculate the stud capacity per AISC ASD 9? The max shear loads at the ends of the slab is 447 plf. Assuming studs at 24" o.c., each stud will have a shear load of 900 lbs on it. This obviously will have a large design margin, but I have to do a calcualtion for this. Additionally, I would probably provide studs uniformly everywhere to reduce the possibility of construction error and the studs being installed in the wrong locations.
RE: Lateral load resistance of slab on metal deck
Dik
RE: Lateral load resistance of slab on metal deck
It is a safety issue too, you need the deck attached in all areas to function as the form for concrete and walking surface. I have never used anything but puddle welds or shear studs when attaching the deck to the floor steel. If the flanges are not too thick, I guess you could use tek screws but seems like a tough day for whomever is using the drill. For your special situation, I would agree with using shear studs everywhere but you should look to make sure they can take any gravity load induced shear in the locations you also need them for lateral.