DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
(OP)
We are working on a project that has tilt-up panels with Brick veneer, is for the goverment. Normally on tilt-up panels your deflection criteria is L/150, on this project they since they have brick they want to limit the defleciton to L/600, which is high for a tilt-up building, not to mention that this project is on a 130 MPH wind zone and a building category IV . This is a warehouse with typical roof metal deck and joists. The design height of the panesl go from 26' with 7' of parapet, and up to 30' high with 3' of parapet. Now, ASCE allows to use 70% of the wind load to calculate deflections, my quetion is, can I design the panel with the full wind load to calculate my steel for bending and then go back again and use the 70% wind load for deflection, since your effective moment of inertia depends on your Ma, this will make a big change in deflection






RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
The original question brings up a good point in that Ie must use an Ma value from a load - and the question is do you use full wind or 70% wind for that derivation of Ie? I would say use the 70% wind.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
In any case, as per the science of construction, one could to follow the actual status at the sections, by segments, to be taken as input in matrix analysis, and this must not be thought as some very extra complication, since (except for the hints given in ACI) one has to work starting with the acting moment, that varies with hypothesis and section.
What brings to my mind the saying of the head of one of the ACI's deflection chapter saying, well say we depend on 10 parameters, make a 5% error on each, so we can't assert our computed deflection be in 50% range of actual. I in fact also remember some people making an analysis at some corner and looking only one of the edge beams asserting some deflection; we showed them that if their computations were ok, the other beam at the corner (under 20 ft span) would have to be showing 4 inches deflection, that obviously did not.
So it comes a point where either the statistical unreliabilities (concrete) or ability to measure (actual material properties of the steel, geometrical imperfections, incorrect restraint assumptions, particularly at tests) severely impair our ability to make a proper prediction of deflections.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
i believe it is on the order of 0.61 or so.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
I have done some bricklaying and brick repair, but I cannot figure out how your archetect is planning on laying a brick wall "sideways" on a flat surface 26 feet wide (it is a tilt-up building right?) and get the mortar and bricks to lay evenly.
How does he expect to maintain a "level" row every time repeatedly when the bricklayers are working "sideways" on some flexible surface (?) or backing plate or work platform that is going to rotate? Surely he does NOT expect to build a standard brick wall horizontally. How will he attach the brick wall to the backing member - with a full layer of new mortar? An epoxy glue of some kind? How long will he need to let the bricks and mortar to dry before that can be lifted up?
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
Why would you build the brick veneer any other way than the normal way? I don't think the OP said anything about putting the brick on before erecting the panels. The masons would work from scaffolds, and the brick would be connected to the concrete backup with brick ties.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
Or maybe precast brick panels that connect directly to the tilt? I've seen these on other projects but never worked with them directly.
Just seems like there is a more economical way to do this, but I suppose in the end its not much different than CMU with brick.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
If the brick is (somehow) laid first, then is he (the architect) requiring the 1:600 deflection just to prevent distortion/cracking of the brick as it is tilted up? Makes no sense, because the distortion from lifting/tilting up a heavy brick wall is going to be almost impossible to prevent without stiffing the wall until it will resist not only wind pressure, but tanks (and cannon and bullets) pressure. 8<)
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
The point here is that it seems that someone decided to place a code restriction at the upper limit of the economical scale of prevention against cracks. Respect cracks as related to distortion, will appear in akin form irrespective of the cause is erection or lateral loading.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
They can find another way to waste the extra cash.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
The deflection limitation for brick veneer is due to lateral loading in service. There are different limitations placed on this by different codes, but L/600 is common, and certainly more easily achieved with a concrete backup than with wood or steel studs.
RE: DEFLECTION ON TILT-UP PANELS W/BRICK VENEER
Is this a a true brick veneer (thick about 3 5/8") or an adhered brick veneer (thin) that is used as a bed when the panel is cast?
In the second case, from a structural standpoint, it is a part of the panel and is controlled by the structural specifications because it moves with the concrete panel.
For an industrial/warehouse building, I would not expect to the real "Cadillac" veneer (3 5/8" thick with flexible ties) that is not connected structurally.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.