Yes, if you have a concrete wall above the footing then there is no reason to use the third bar in the top of the footing. Also true if you have horizontal bars in the masonry, but typically, we use horizontal masonry type reinforcing only. I haven't had any issues from a footing since I...
Kootk, The wall above the footing is typically masonry - usually a brick veneer with a 8" block backup. It is not integral with the slab. In the past I have seen engineers place two bars either 3" clear from the bottom or 2" clear from the top - since it is temperature reinforcing it is okay...
A few years ago my engineering firm starting placing longitudinal reinforcing for non-load bearing wall footings in two layers - two bars in the bottom of the footing, and one bar in the top. I am referring to footings that are typically about 24" wide by about 12" thick, and technically are...
Does anyone have advice on selecting a grade for old lumber that was sawmilled before the current grading system? I am looking at engineering a renovation of a 100 year old building, constructed with lumber which is obviously a better grade than #2 SYP. Are there experts who can evaluate the...
The Sinak products look impressive, but they do not seem to be for interior slabs that will receive a floor finish. I know that wet curing is really the best way to go, but still wondering if that is the most commonly specified method for interior slabs. Most of the General Contractors in my...
I noticed that MasterSpec doesn't allow a spray cure compound for floor slabs to receive a floor covering, i.e. a form of wet cure is required. I know that dissipating spray curing compounds sometimes do not dissipate if they are not exposed to light and foot traffic, but they still seem to be...
Definitely use control joints or you will end up with shrinkage cracks in the block. Brick will expand over time, but the cmu will shrink. I have seen many jobs where the control joints were omitted, and the cmu formed shrinkage cracks.
...a website called engineeringtoolbox.com. Their example is for a car crash, and for a human falling from a table. The formula is F = 1/2 x m x (V*2)/S, where S is the deflection or distance over which the force is absorbed. I calculate F = 1/2 x 15 lbs/32.174 x 132 x 132/S = 4061 lbs/S. To...
Thanks WARose. The slowdown distance may be a misnomer, since it came from a physics text where the example was a car crash test. I think it is the deflection, since the unit is in feet or inches. I'll check out Blodgett - that's a great book.
Mike20793, thanks for the Texas Tech...
I am designing a safe room for tornado loads and wondered how other engineers are calculating the force due to 2x4 missile impact. I think the appropriate formula is F = 1/2 x m x V x V / S, where S is the slowdown distance. The appropriate mass seems to be 15 lbs / 32.174 = 0.47 slugs, and...
I'm trying to figure out what has caused this crack pattern in a precast stadium beam. The cracks do not look like tension or shear cracks - maybe they are just shrinkage. The beam is about 3 feet deep and 14" wide. The predominant pattern is 3 or 4 longitudinal, with some random vertical...
Turn down the exterior edges of the slab so that they extend below the frost line is the best way when you are in an area with a relatively shallow frost depth.
Spats, I have calculated this design many times, and it sounds like you probably have too. I count on a certain amount of the slab working with my footing - usually at least a 3' cantilever from the footing, but maybe more, depending on how the slab is reinforced. I also count on a certain...
PEinc, yes, the way I have always calculated in the past is to use 1.5 x sliding force < (0.45 x DL). Or to use another value for friction factor based on the type of soil actually used. smvk3, sorry I jumped in without fully understanding your question. I think applying 0.6 to the DL to...
SMVK3, this is one reason why I don't like to get the coefficient of friction as provided by the geotech. If you design a retaining wall for 0.3, and then apply a factor of safety of 1.5 against sliding, you will end up with a very very conservative design. I asked this same question once of...
Be careful with the welding procedure. Your original sketch looks like a no-throat fillet weld. Maybe a bent plate in the shape of the two angles would work better, and eliminate the welding.
I'm curious as to the different ways to hire a special inspection firm. Many of our clients prefer to hire a qualified favorite firm and just pay their hourly costs on a monthly basis, but some clients prefer to have a "fixed fee." I have found that a fixed fee is nearly impossible to arrange...
