RAM Concept - Mat Foundations 2

[TwelveRox_12]

Hey guys, this might be a bad question, but I really want to know this. So recently I designed a raft foundation with column drop panels, my superior suggested to merge the column drop panel to become a column strip so that the overall depth of the "merged drop panel" strip can be shallower. So then now I want to design the column strip in RAM Concept, but I've used the drop cap, and make it to a really long drop cap, but the analysis failed. Anybody can give a lesson or two? Thanks.

P/s : I need to know the new depth for the column strip.

 

[structSU10]

what is the intended function of the drop cap? do you need more shear capacity? are you trying to reduce flexural steel at column strips? how are you modeling - in concept directly or as an export from structural systems?

 

[TwelveRox_12]

Hi, thanks for the reply @structSU10, the strip (drop cap) was intended for punching shear (drop panels), but superior recommended to change it into strips, we then proceed to take the highest depth of the drop panel, and thus taking the deepest drop panel along the x-axis and make it into a strip. However, there are several depth for the strips and the the difference is relatively high (first strip; 800mm, and last strip 500mm), so my superior asked me to "standardize" the depth to be all same, but we can't make the whole mat thickness to 800mm as this structure already considered over-design, if we make all into 800mm, then it would be even more massively over design, therefore I need some ways to standardize the depth so that the contracts wouldn't get confuse as to the different depths during excavation. As for my modelling, I import drawings from CAD, and then model using RAM Concept (Slab, Column..etc)..

Thanks!

Best regards,
-TR

 

[structSU10]

All you need is to know the minimum thickness for punching shear which would be based upon your worst case punching condition. You can model the slab at minimum constant thickness first, run a punching shear check, and find the worst case. From there, determine thickness at the depressed strips, and run them at least as wide as the punching shear perimeter, probably a little wider.

Alternatively, you could design the slab for constant thickness and provide shear reinforcement for the punching shear where required. It will simplify construction for your main rebar layers, and have a constant site prep, which should be able to justify the punching shear reinforcement.

 

[SethGuthrie]

For more on drop caps (which tend to be for punching shear only) and drop panels (which are also considered for flexure) in Ram Concept see this:

https://communities.bentley.com/pro..._and_design__wiki/cross-section-trimming#drop

 

[TwelveRox_12]

@structSU10 : Thanks for the recommendation!! Definitely trying out.
@SethGuthrie : Thanks, I will have a look at it.

 

[TwelveRox_12]

Hey guys, can anybody help me check? I'm constantly getting punching shear error at the edge of my raft foundation. I'm very new so I only followed the tutorial from the RAM Concept manual. Please do explain to me, too if you don't mind. Thanks!

 

[SethGuthrie]

It's often difficult to get punching shear to work when you have a heavily loaded column right on the edge of the slab. The eccentricity of the reaction to the failure plane is the biggest issue. If you can't make the slab bigger, then an edge beam might be required. For more see:

https://communities.bentley.com/pro...18.ram-concept-punching-shear-checks-faq.aspx