Detailing with concrete

[GalileoG]

My experience has been with structural steel, though lately I have been designing reinforce concrete elements (beams and columns.) Soon, I will be working on the design of a three storey reinforced concrete building but realized how little I know about concrete detailing/connections.

For two beams spanning into a column on opposite directions, how would you detail the connection to act as simply supported and how would you detail the connection to act as a moment frame? Are there are free references online that could be of assistance in my quest to understand concrete detailing?

Clansman

 

[jike]

Because of the monolithic nature of poured in place concrete, the connections are usually rigid between elements and not pinned. An exception might be an expansion joint where a beam or a slab might be bearing on a bracket.

I suggest you that you discuss this with the engineer that mentors you. Also check out the ACI detailing manual, CRSI, other similar projects that your company or others have done.

 

[youngstructural]

As Jike has alluded to, it is essentially impossible to have this as a pinned connection... You might be able to safely assume pin in your analysis, but more likely than not you need to consider the effects of fixity.

Essentially this means that you will be attracting additional axial load onto the column below (from the T-cantilever effect) as well as reducing the positive moment in the beams.

There are a number of excellent texts, but if you're starting from cratch, the best IMHO would be "Reinforced Concrete Structures" by Park & Paulay. Hasn't been updated (that I know of) since 1975 and is still the authoritative text on the subject.

I stand ready to be corrected, but will be VERY surprised if I am.

Regards,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[NS4U]

look up structural integrity reinforcement in the code... this would be a case where that would need to be applied

 

[asixth]

I wouldn't assume the beams are simply supported.

The deflections will be excessive, the positive moment will be excessive and the negative moment will be under designed.

 

[abusementpark]

If you want to take the conservative, easy (yet simple) way out, you could determine area steel required based on simple supports and provide that at top and bottom. That would cover any negative moment. Deflection will be negligible if you consider the joint to be rigid. I have heard of some people rarely checking deflection for general concrete construction. I am not championing this mindset, just pointing it out.

 

[edwin17th17]

i feel your pain man.. dont know much about concrete either.. my advice is to get a lot of books regarding concrete.. CRSI, ACI, etc..
dang am planning to take up nursing sometime..
am done being an engineer.. =)

 

[civilperson]

Simple supports have 300% more positive flexural moment strength required at the center than fixed end supports with the same loading need at the center of the beam. Use the correct beam formulas for sizing reinforcement and develope the reinforcement beyond the inflection point or beyond the location of necessary flexural strength. Keep splices out of congested regions, (such as column connections).

 

[GalileoG]

Civilperson, how far beyond the inflection point do you extend the bars?

 

[JAE]

Clansman, if you are designing under ACI 318, there is a diagram in that code in chapter 12 that identifies where you should extend top bars past the inflection point.

 

[rheim]

Clansman,

I found the following books very helpful for the design and detailing of concrete buildings:
1. Simplified Design (Iyad M. Alsamsam/Mahmoud E. Kamara), published by Portland Cement Association
2. Essential Requirements for Reinforced Concrete Buildings, published by ACI International
3. Placing Reinforcing Bars by Concrete Reinforcing Steel Institute
All are very practical, not overloaded with theory. The third one is actually written for iron workers and gives you a good grip on the practical side of the construction process
Hope this helps