If the pedestal is significantly oversized due to geometry, I would be willing to let the reinforcing ratio go as low 0.005, treating this as an "architectural" column. The way PCA Column designs "architectural" columns by reducing the effective concrete area so that...
You should design the pedestal for the capacity of the braced frame as determined by the probable brace capacity. Assuming you do this, the pedestal can be designed conventionally because it will not require significant ductility.
How real is your live load?
In general, I prefer not to camber for more than the dead load deflection because most of the time the real live load is much less than the design live load. If the structure is cambered based on the design live load, most of the time the structure will have a...
In theory the pre-existing stress in the deck would effect the deflections because instead of the entire section of the deck reaching yield strain simultaneously (as would happen with a reinforcing bar), the plasticity will propagate across the depth of the section. Before the deck starts to...
1) Yes. It is called a "shear head" and is covered in Section 11.12.4 of ACI 318-02.
2) Yes.
3) Shear strength on the reinforced section is limited to 7 root f'c.
4) Looking at the ACI website (www.concrete.org), I do not believe that it is available for download.
I agree with VOD's comments, though from a somewhat different perspective. While your proposal would target the same probability of failure for the building during it's "life", the risk to an occupant of the building during any given time period would be increased. Since our primary...
If you're looking for more theoretical background, I've seen a fair amount of research published in this area, mostly in ASCE's Journal of Structural Engineering. You might start with their searchable database at http://www.pubs.asce.org/cedbsrch.html . One article that looked promising was...
Design Guide 6 only covers W shapes embedded in concrete. Concrete filled pipes and tubes are covered in the LRFD version of AISC's Manual of Steel Construction.
I should have also pointed out that this is not just an issue for the structural consultant. The Murray criteria is only considers footfall induced vibration. The lab equipment is also susceptible to vibrations induced from other sources like mechanical equipment. The MEP consultants will need...
1) In my experience, the vibration limits in the steel book are consistent with what a knowledgeable lab consultant or vibration consultant would give you.
2) Unless on slab-on-grade, electron microscopes are almost installed with their own vibration isolation mounts. Presumably that would also...
ACI would allow the tendons to be uniformly distributed in both directions. The problem with doing that, however, is that it will make the placement of the tendons quite complicated. When tendons are banded in one direction, the banded tendons can be laid out first, and then the distributed...
It really depends on how you have analyzed your slab. If you have analyzed it using the equivalent frame method, then your unbalanced moment in each direction is the result of taking 100% of the load in that direction. Clearly, it would be rather conservative to check punching shear combining...
The Brick Industry Association has numerous technical bulletins on their website: http://www.bia.org/ .
At least two of these discuss corrosion of ties.
You might also take a look at FEMA-353 "Recommended Specifications and Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications." It has at least a couple paragraphs discussing the use of non-fusible backing bars. There may be additional discussion in...
I find the AISC Design Guide 3 "Serviceability Design Considerations for Low-Rise Buildings" helpful in this regard. It covers allowable deformations for vertical and lateral loads, and considering a variety of non-structural systems that may be affected by those deformations. I would...
In both of the situations described I would provide some minimum reinforcing. Even though you have designed the structural element to be simply supported, the reality is that there will be some fixity until the concrete cracks to release the fixity. It would be prudent, then, to provide some...
I'll try to answer a couple of these:
0.9 x D + ??? x L + 1.3 x W
If the live load has a favorable character, it should not be included. If the live load has an unfavorable character, I would use a load factor of 1.3. (or 1.28 if you prefer.)
The 1.3 factor is just a simplification of...
The portion of ACI 318-99 that JAE referred to tells the designer to calculate an index "Q." If Q is less than 0.05 for any given story, then that story can be considered braced. Q is calculated by (Sigma Pu x Delta0) / (Vu x lc ) where:
Sigma Pu = the total vertical load at the story...
I haven't experienced this personally, but there was a good article on this in the October 1995 Issue of Modern Steel Construction. The article was by Thomas J. Langill and Tom Schlafly and was titled "Cope Cracking in Structural Steel After Galvanizing."
AISC should be able to...
