Opening at a RC Wall/Column 3

[otto_eng]

Hi Folks,

I have a 6 story height RC wall/column that is taking only minor vertical load, not a big trib. area. I need to have some holes at each bottom corner of this element to locate precast landing connectors. These holes will be grouted after the connectors are placed inside of the hole. Would that be an insufficient and sloppy check , if I could justify the width and depth of the column as the only part that is taking the vertical and not consider the parts that are disturbed ?
Any good practical resources that deals with these kind of problems in RC ? or do you guys bring out your knives and go for a strut & tie duel ?
Thanks !

 

[HTURKAK]

I would not go with strut & tie model but simply reject this solution without compromising which may endanger the strength and behavior. There should be other suitable options.
Pls provide more details to get better responds.





Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[Lomarandil]

I disagree with HTURKAK here. If you're proposing to ignore/subtract the impacted area and evaluate the narrower net section, that is certainly a viable approach. I think there will even be methods to consider the gross section without turning to S&T if merited.

 

[Agent666]

Any reason they can't just cast in these connectors with the wall panel.

Either way if the infilled concrete/grout is done along the lines of a proper structural repair and the wall reinforcement carried through I'd see no issue with it. Concrete is removed and replaced all day long in the repair industry, so if you were to infill before the next level is added or something I don't really see any issue. Not sure what form these connectors are to really comment further, imagining some sort of cast in plate?

https://engineervsheep.com

 

[otto_eng]

The proposed design involves using precast concrete for the landing and staircase, preventing connectors from being cast-in with the walls (cast-in-place) due to the precast landing installation and the limited space prohibits extending bars at connector locations.
Although stress concentrations will happen at the inner corners of the openings, my initial analysis indicates stress remains within the concrete design limits, with the option to locally upgrade to C40. My concern lies in the openings being positioned at the edges rather than the center.
Am I missing any other checks here considering both mechanics of materials and practical constraints ?

 

[HTURKAK]

Mr . loti_eng ,

I looked to the last picture and could not see the reason for holes having dimensions 270mmW X 150mm H. IMO , 150 mm X 150 mm should be OK and will be less disturbing.
I would consider the following variants ;

- CIP landing monolitic with walls and beams . Just the flights would precast,

- Cast the connector box with wall panels and use telescopic corbel (tragelement in your picture ) . RHS at the landing will be 150 mm long with open top and the solid corbel pushed thru connector box during installation.

- You did not mention the formwork system . Say jump formwork. Another solution , install RHS box outs ( bolted to the formwork ) and use rectangular solid hidden corbel , the landings would have channel shoes .

PS: I checked the nominal stresses at the rc wall seems OK but not sure for the beam shear (as far as i understand , 3 of the connections would be located )







Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[Rex Hang]

It's great that you're considering the practical aspects of your design. When dealing with openings in reinforced concrete elements, especially in cases where only a small portion of the column is carrying the vertical load, it's crucial to assess the structural integrity and redistribution of forces.

While justifying the width and depth of the column based on the part carrying the load is a reasonable approach, it's equally important to evaluate the overall structural behavior and potential redistribution of forces in adjacent regions. The disturbed zones around the openings may affect the load path and could lead to unintended consequences.

To address this, a thorough structural analysis using methods such as strut-and-tie modeling would indeed be beneficial. This approach considers the disturbed regions and helps ensure that the load paths are appropriately accounted for. It's like bringing out the knives, but in a controlled and analytical manner.

As for practical resources, publications from organizations like the American Concrete Institute (ACI) and relevant design codes can provide guidelines for handling such situations. Additionally, academic resources and case studies on similar structural modifications can offer valuable insights.

Remember, safety is paramount, and a comprehensive analysis will help ensure the structural integrity of your design. Good luck with your project!

 

[ALK2415]

@ loti_eng
you could change the seat detail to be full steel ring inside the column-wall
would not cost much and will work as integral part of the RC column-wall

 

[otto_eng]

thanks all! this is closed.