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Hi, We're working on a project where we're way under the water table. We have a 24" pressure slab. The negative reaction at some columns is over 500 kips. Should this load be included in the column design? (The load in the columns is enough to counteract this) Thanks, Matt

That's very interesting. I have almost an identical situation and I'm trying to figure out what I want to do. What did you end up doing? -Matt, EIT

Thank you for all the input. I think that I'm going to size my beam so that it's 4" shallower than my exterior pile caps (my piles are embedded 4" into cap) and have the top of the beam be flush with the top of the pile cap. I will design top steel reinforcing using a simple strut and tie model...

Hokie, I tend to agree with you. There are plenty of examples for common strut and ties applications (e.g., deep beams, corbels, etc.) but not really any for pile cap strap beams. For the d-region (which I agree with you is really only the cantilevered portion), do I require the minimum...

I'm not sure if the beam would have continuous uniform support. It seems to me like it would behave more like a deep cantilever with concentrated loads... I feel like a strut and tie approach would be applicable. I can't really find any resources for this anywhere. It would be easy to just say...

Hi, Does anyone know of any good resources for this? I feel like this is different than a traditional strap footing. Thanks, Matt, EIT

The interior column is an appreciable distance away and I see your point. There exists other criteria for deep beams though, such as if a concentrated load is applied very close to the support allowing compression struts to form... I feel like my situation falls into this category.

Warose, Thanks for the reply. I have designed traditional strap footings like you have said and I have a pretty good feel for that type of structure. The project I'm working on now is an 8 story concrete building in NYC. It's in the east village so the soil is bad and the bedrock is...

Hi, How does a strap beam for a pile cap differ from a traditional strap beam for spread footings? Since I have a short, deep cantilever, do I need to design using the 'strut and tie' method? What would I use for the width of my struts/nodes if this is the case? Also, would I have to adhere to...

Hi, How does a strap beam for a pile cap differ from a traditional strap beam for spread footings? Since I have a short, deep cantilever, do I need to design using the 'strut and tie' method? What would I use for the width of my struts/nodes if this is the case? Also, would I have to adhere to...

Thank you for the response; extremely helpful. I just have a few follow-up questions though regarding the ACI 318-11 code 21.9.5.2 about effective flange widths for special structural walls. Does this apply to ordinary reinforced concrete shear walls? There seems to be very little requirements...

If I have an arbitrary shear wall shape (e.g., an h-shape) or something similar to that where I have wall segments branching off, are there any limitations on the reinforcement design? I'm designing my wall as an ordinary reinforced concrete wall. I will apply positive and negative moments about...

Hi, I have a situation where a small portion of my beam is a d region, which has governed my design. This required additional reinforcing such as longitudinal shear reinforcing. Once I'm out of the d region, can I terminate some of this "special" reinforcement? Please see attached sketch.

Dadomago75, when you say M33 for piers, I don't see M33, did you mean a different parameter?

Thanks for all the advice. Bookowski, very good article. Also, the article referenced in your article is very good as well: " A very good resource for an in depth discussion of the backstay effect and recommendations for modeling is Modeling and Acceptance Criteria for Seismic Design and...

also, bookowski, I have thought about your opinion before you posted it, and i tend to agree with you. However, I feel like if I'm trying to think of the wall behavior in the most realistic way, wouldn't the first floor slab put a force on the wall... and then would the slab on grade put another...

Thanks for the input. This question is not aimed towards a specific project, but yet a reoccurring situation I run into. Typically, most of my projects are 5-10 story concrete buildings with 8" slabs. Also, what if I had a shear wall in the same plane as the peripheral foundation wall, would...

Hi, If I have a shear wall spread footing located in the center of my building, with a large overturning moment, should I design my footing for gravity loads only, or gravity loads + overturning/shear? Some have told me that the first floor slab takes lateral forces to the peripheral foundation...

Hi, Our office just landed a project for a 13-story load-bearing masonry wall building. My boss told me to find a good software program to use for masonry analysis/design. We'll probably use the software for gravity and lateral loading. Can anyone recommend a good software program? Thanks!