In section 9.2 of the sixth edition of PTI's Post-tensioning manual, they have a step number 5B - Calculate Post-tensioning force using "allowable average compression". I realize that this step isn't a code enforced step of the design, but more of a rule of thumb (an unwritten rule, to be...
A supervisor went to a seminar on PT Design. In the seminar, they defined something called a "Slab Band" or a "Drop Band" as a slab thickening used primarily to get more drape on your banded tendons, but was not to be designed as a beam (ie, no beam shear steel). Limitations were placed on the...
I have an elevated plaza/parking slab on a condo project we are working on. There is a daylight basement type of parking beneath the building, and an area of parking on the 1st floor slab. There is retail shops and restaurants going in on the first floor, so the owner wants to have delivery...
I have heard from some engineers that it is more economical to avoid drop caps for punching shear by adding up to some number of inches of concrete. The thinking is that a good majority of cost in concrete construction deals with the formwork materials and labor. (This seems to be similar to...
I am relatively inexperienced with concrete slab design, and had a few punching shear issues to get worked out that are outside of the cookie cutter examples found in the ACI. Note that this is my first Slab design and I am working under a supervising engineer who has a lot of experience in...
In ACI 318-02, section 18.3.3, it defines the different classifications of PT Slabs, with type U being the typical uncracked PT slab with the tension stress limit equal to 7.5 (f'c^0.5) (which is increased from the 1999 and earlier codes which put the limit at 6 (f'c^0.5)). At the bottom of...
I was looking at using a light gage top track to distribute loads to load bearing stud walls, which I have never even explored before. In looking at deep leg tracks (user defined as 600T400-68 and 600T600-68 in the programs that I have), you find out that those types of tracks have all kinds of...
We have a client who does traffic signal structures for different jurisdictions. This isn't our normal line of work, but we know how to use the AASHTO 2001 "Highway Signs, Luminaires and Traffic Signals" code, and it is just like any other type of structural design.
Anyways, the project that...
I have the latest RamSteel with the floor vibration software, the AISC Design guide 11, plus several articles written by Thomas Murray (co-author of Design Guide 11).
With all of this information at my hands, I still question whether I am using the design recommendations correctly, at least...
Trying to determine the impact force from an object falling from multiple stories . . . we will have a wood platform that we need to design so that it stops the object. To refresh everyones' memory, the average force is called "impulse" and is equal to the change in momentum divided by the time...
I have an application with whole logs being used, basically the only milling done is having the bark removed. I was wondering just how strong a log is when compared to sawn lumber. You would think that leaving the cell structure of a log alone would be stronger than the individual pieces of...
I have a steel joists and joist girder book by Vulcraft dated 2003 that I used to make decisions on a complicated joist project that I have. The winning bidder on the project is somebody other than Vulcraft, and they have some questions, which they qualify by saying "per SJI." Is my Vulcraft...
I need to support some brick veneer over the top of my roof decking, and my roof decking is sloping at 3-1/2" to 12" approximately. Can I slope the steel lintel that the brick sets on cutting each individual brick, or would the brick slide right down the slippery steel angle? The other...
There are no hard and fast rules for the deflection of a composite steel beam under the weight of wet concrete (talking about unshored construction). Just wondering what engineers have come across and apply in their designs.
Do you limit the deflection at all, even if the beam is to be...
In the 1997 UBC, Special Concentric Braced Frame connections were required to be designed for the lessor of three cases. 1) Tension Strength of brace; 2) Omega times the calculated earthquake force plus all applicable gravity loads; 3) Max force able to be transferred to the system.
Well...
We have some big cantilevered architectural canopy, where we have 1-1/2" diameter tension rods splaying out from a vertical column (similar to a cable stay bridge). Well, the rod that goes to the end of the canopy is about 31' long at a 45 degree angled slope, doing a beam deflection...
Anybody know where to find out how much of a radius different HSS shapes have at their corners. I know this depends on the thickness of the tube wall. In the welded joint tables, the flare bevel weld shows that the radius C is three times the thickness, which could be 1-1/2" for a 1/2" thick...
We have a whole series of two story steel structures (5 building total), and the architect is showing a pitched roof with hips and valleys, much like is typically found by framing with gang-nailed wood trusses.
The shape of the roof just screams light gage steel trusses, but with all kinds of...
I asked a question the other day about getting loads on a crane outriggers . . . well, now I am shoring for that crane to drive out onto the slab it is going onto, as well as shoring for the outriggers.
I haven't done a lot of shoring, so I don't know if I am missing something obvious . . . it...
We've been hired by a contractor to look at how much shoring will be required in order to drive a crane onto raised concrete slab. Its a series of one way slabs spanning between beams that are in some cases conventionally reinforced and in other cases post-tensioned. I have the outrigger loads...
