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RE: Concrete Filled HSS Section

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It’s not a situation where a base plate can be used.  It is a vertical HSS section embedded in a concrete trench.  The HSS section does not extend to the bottom of the trench, therefore there is still a moment component to be transferred at the bottom of the HSS section into the remaining concrete section (trench) which is below the HSS section.  The HSS will be filled with concrete and a length of reinforcing placed in the concrete within the HSS section.  I agree there are no “warm and fuzzies”, and don’t really agree with this solution.  I am just reviewing possibilities at this time and making comments.



From: Gerard Madden, SE [mailto:gmse4603(--nospam--at)]
Sent: Wednesday, May 28, 2008 8:37 AM
To: seaint(--nospam--at)
Subject: Re: Concrete Filled HSS Section


I second these comments...


On Wed, May 28, 2008 at 7:19 AM, Scott Maxwell <smaxwell(--nospam--at)> wrote:

Why going to all that effort?  What not just design the base plate appropriately for the moment and the anchor rods to properly handle the moment at the base of the HSS like you would typically do for a rotationally resistent base at the base of a steel moment frame?  You are more than likely going to get a better moment connection/rotational resistance than what you are talking about.  Frankly, what you describe does not give me too many "warm fuzzies".  Even beyond the bond issue, you are not going to get much moment capacity as your moment arm for a rebar in the center of the concrete will not be that great, unless you have a rather massive HSS section.





Adrian, MI

-----Original Message-----
From: Joseph R. Grill [mailto:jrgrill(--nospam--at)]
Sent: Wednesday, May 28, 2008 9:44 AM
To: seaint(--nospam--at)
Subject: Concrete Filled HSS Section

I'm looking at a proposed design where an HSS section is filled with concrete.  At the center of the concrete section a length of rebar will be placed for the height of the section.  One end of the filled HSS section will have to transfer moment from the filled section into a concrete base.  The idea, I'm guessing is that the rebar in the center of the HSS section, (which extends into the concrete base) will transfer the required moment into the concrete base.  I guess it is possible, however, I have a question. The rebar, that extends into the filled HSS will be in tension.  What embedment length into the column will be required.  I think it would be the standard tension development length, but what length of concrete fill would be required to bond the concrete fill to the HSS section.  I've looked at the AISC specs for this type of member, but I don't see any mention of this.