Composite Building Connections

[2204z]

What are the ways to add steel storey to existing reinforced concrete structure? Where to connect it. Can you rely just on expansion bolts and metal plates to connect the new steel story to concrete pedestals? Would these steel connections be as strong laterally and seismically as monolithic concrete connections in pure concrete structures? What is the usual Pro and Con? Thanks in advanced to those who can help.

 

[KootK]

Ideally you'd want to place your new steel columns directly upon the existing concrete columns. The connections almost certainly would not be as strong as continuing monolithic concrete would have been. Usually, however, the majority of your steel columns would not be used for lateral resistance. Usually, only a few discrete columns will be braced or existing shafts will be extended.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[2204z]

Ideally you'd want to place your new steel columns directly upon the existing concrete columns. The connections almost certainly would not be as strong as continuing monolithic concrete would have been. Usually, however, the majority of your steel columns would not be used for lateral resistance. Usually, only a few discrete columns will be braced or existing shafts will be extended.

For parking on steel decking as additional floor.. would the connections be able to support the entire new floor under lateral loading.. connections based only on bolts and metal plates and nuts?

Without bracings (as there is no space for braces). If seismic acceleration of the parking floor occurs, won't this shear the bolts and nuts in the metal plates?

Or is it not recommended at all to add a steel storey if there is no bracings no shear wall of any kinds in the storey that has the connections?

 

[hokie66]

Your query is difficult to answer without knowing the whole story. It is of course feasible to design a rigidly framed steel structure, in both directions, without bracing, but that is not a very economical solution, and may or may not work with your existing structure. So it is fair to say, it depends....

 

[KootK]

For parking on steel decking as additional floor.. would the connections be able to support the entire new floor under lateral loading.. connections based only on bolts and metal plates and nuts?

As Hokie said, it depends on the particulars of your situation. Similar strategies have been successful in the past but that's no guarantee that it will work here. You've identified a critical connection that will require careful design. The next step is to attempt to design that connection.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[2204z]

Ideally you'd want to place your new steel columns directly upon the existing concrete columns. The connections almost certainly would not be as strong as continuing monolithic concrete would have been. Usually, however, the majority of your steel columns would not be used for lateral resistance. Usually, only a few discrete columns will be braced or existing shafts will be extended.

Were you describing putting new steel column on one meter of concrete column? What would create stronger connections? Making the concrete column full column and only use steel beams to connect to concrete column or using steel column connected to concrete column?

 

[KootK]

Connecting new steel columns to the existing concrete may work just fine 2204z. You just need to run some numbers to verify that.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[2204z]

Connecting new steel columns to the existing concrete may work just fine 2204z. You just need to run some numbers to verify that.

But if we just complete the concrete column since we have many cement left for that and use I-beams, metal plates, expansion bolts, etc.. how would this compare to one with steel column? For seismic resistance.. would steel beams on concrete columns.. or steel beams on steel columns be better generally?

 

[hokie66]

I thought you said you were intending to add this floor to an existing structure. Adding new concrete columns would likely be more complicated than using steel.

 

[KootK]

It mostly depends on the connection between new and existing I'd think. If no provisions have been made fore extending the concrete, I would also vote for steel columns. If there's rebar projecting out of the columns, or couplers cast into the tops of the columns, then new concrete columns might be preferable.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.