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  1. VTPE

    Underground Parking Structure

    We have done several underground garages and had to learn a lot through them. We are in Buffalo and have built in Boston (6 and 3 floor down), Milwaukee (4 floors down), and elsewhere. Here are a few suggestions: 1.) I would not use expansion joint unless you have unbalanced earth laods. If...
  2. VTPE

    Shear Friction: Where and When?

    See attached. A simple FBD ives the answer. Also, remember why reinforcing is there. The reinforcing and concrete have the same stress until the concrete cracks, then the reinforcing acts alone. (compatibility analysis anyone?) Once the concrete cracks, there would be no shear friction since...
  3. VTPE

    EnerCalc

    For my two cents, I found Ram Elements pretty good. Tedds is VERY limited. You can write code in tedds, but it is not in any standard programming language. Further, if a peice of informaiton changes in the middle of a calc, it is not re-sent back tot he beginning unless you direct it to. For...
  4. VTPE

    CRACKING IN POST TENSIONED BEAMS

    Is your slab tensioned too? Primary stressing perpendicular to beams with T&S stressing parallel to beams? The beam may be trying to shorten but be restrained by the slab so the system is relieving the stresses through cracks.
  5. VTPE

    Robot, Risa3d or another

    We use Ram, Risa, and Etabs for most calculations with internal spreadsheets and Tedd's for general purpose calcs. We used Staad int he past but gave up on it when we got Risa. The Ram suite is excellent for steel buildings and only OK for concrete. The way it calculates (from the top down)...
  6. VTPE

    #78 Aggregate in Concrete Mix

    Typically, you want a well graded mix to reduce the amount of cement and to provide larger stones for better strength. I would suggest that is you do allow the #78 stone, that you limit the amount of cement (say to 540 #/CY) so that you do not get excessive cracking, especially in an elevator...
  7. VTPE

    Wind Kd Factor and Drift

    I have a question on the wind load provisions of ASCE 7-05 that I thought I would pass around. Article 6.5.4.4 – Wind Directionality Factor says that Kd (=0.85 for MWFRS and C&C) , “Shall only be used with the combinations specified in section 2.3 and 2.4”. Those (2) sections are the LRFD and...
  8. VTPE

    New Steel Beam to Existing Concrete Column connection Design

    I would argue that friction connection does not provide a positive load path as the friction force is dependant on the clamping force that may relax over time. Both IBC and AISC require positive load paths.
  9. VTPE

    Veneer relieving/shelf angles

    AISC publishes a guide for single steel angles. In that it talks about bending of angles abotu axes other than the primary axes (which is what you are describing). Basically, you take the elastic deflection and multiply it by 1.86. This accounts for lateral torsional deflections of the angle...
  10. VTPE

    Low permeability, Low Shrinkage Concrete Mix

    If you have the money, you could add silica fume to the mix. Very fine pozzaloans tend to make the concrte less permeable. Also, consider using a blended (steel and poly) fiber and no WWR. This tends to make the concrete tougher.
  11. VTPE

    Structural Textbook for Architects

    I had the opprotunity to teach a structural engineering class to graduate architects focusing primarily on Concrete design, foundations, and some lateral analysis. Does anyone have a suggestion for a GOOD but SIMPLIFIED textbook. Remember, I will be teaching Architects. The idea is to give...
  12. VTPE

    Double top plate on stud wall

    That interior non bearing wall is a problem unless it is detailed correctly. If that wall takes load, the I-Joists go into reverse bending putting the bottom flange in compression. Those elements are not typically designed to be unbraced, so you could have a serios lateral torsional problem...
  13. VTPE

    Anchor Bolt Detail Question

    if you are in a seismic design category C or worse, the ACI makes it very difficult to use hooked anchors. The preferred method these days is to use straight anchors with heads or nuts. See the ACI 318 code for requirements for anchors in concrete.
  14. VTPE

    Composite Deck - Reverse Bending

    Unless you can determine that the deck is developed by its interaction with the concrete and that it has yeilded, you can not expect the deck to work as reinforcement. Even if the deck has deformations, it would be difficult to provde it is composite. Further - I think ACI has limits on the...
  15. VTPE

    concrete / shrinkage vs strength gain

    I did (2) similar garages. The first, we tied the slab into the foundation wall and spent the next year chasing cracks. The wall will be extremely rigid, even after the shrinkage is out, the slab will tend to move. If it is restrained, you will get cracking. The second garage we detailed a...
  16. VTPE

    How to work 2D problem in risa 3D

    For 2-d frame problems, restrain vertical torsion in one support. - Restrain horizontal and vertical translations in the same support. Restrain vertical and out of plane translations in the second support. Be sure not to pin both the end of the member and the support or you will have a free...
  17. VTPE

    Explain ASD vs LRFD to a dumb ME

    There are a couple of important things to realize. 1.) The ASD Manual (the Green Book) has not been updated since 1989. The specificatyion part of it has not been updated since the 70s. All current research has been conducted using limit stares design. 2.) In ASD, the factor of safety is...
  18. VTPE

    soil pressure with 0.6D+W

    Most Geotechs will be giving you NET allowable soil bearing pressure based on SERVICE loads considering depth of footing, overburden, surcharge, and size / shape of footing. That means, the bearing pressure that is allowed at the depth the footings are presumed to be placed. Consider a...
  19. VTPE

    Pumping Fiber Reinforced Concrete

    Are you using Light weight concrete? have you ahd the fiber manufacturer talk with the contractor. I had a similar situation in Boston. After we got the manufacturer involved, the pumping was smooth as silk.
  20. VTPE

    Roof Live Load Reduction

    If you read the code carefully, it states that only the loads stated in the Live Load Table are reducible. neither minimum roof live load, paritition loads, nor snow loads are listed in that table, so by the letter of the code, they are not reducible. Please note that yes, i did say partition...

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