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RE: Moment Connections

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Refugio:
I am also looking for some reference for steel beam to concrete column
connections.
Here I have got some info regarding these special connections which I
got from net. Sorry to tell you that the figures are not available.

Regards
Ashraf 
***********************
------------------------------------------------------------------------
--------

 

RCS Frame Systems

 

Composite moment frames evolved in the United States during the late
1970's and 1980's as a variation of conventional steel moment frames in
mid- to high-rise buildings.   Later in the 1980's, similar systems were
being developed for low-rise construction in Japan.  The composite
frames typically resemble conventional steel frame construction except
that the steel columns are replaced by high strength reinforced
concrete. The primary motivation for this is a 10 to 1 cost advantage of
concrete over structural steel for resisting compressive column loads
(Griffis 1992).   Innovative construction staging operations also reduce
the cost and construction time. As shown in Fig. 1a, a typical
construction sequence utilizes small steel erection columns to advance
steel framing several floors ahead of placing reinforced concrete
columns.   Shown in Fig. 1b is an alternative precast construction
method that has been applied to low-rise buildings in Japan.  In this
scheme, the steel beam is cast integral with the column and field
spliced a short distance away from the column face. Variations to these
methods, such as utilizing the column reinforcing bar cage as the
erection column have also been developed. 

 

  

(a)
(b)

Figure 1.  Alternative construction methods for composite framing
systems (a) cast-in-place with steel erection columns, (b) precast. 

 
Beam-Column Connection - Design and Behavior
 

 Shown in Fig. 2 is a typical beam-column connection for composite
frames where the steel beam passes continuous through the joint, thereby
avoiding interruption of the beam at the column face. This eliminates
the need for welding or bolting the beam at the point of maximum moment
and, thereby, avoids fracture problems encountered in welded frames
during the 1994 Northridge and 1995 Hanshin earthquakes. The concrete
column reinforcement runs continuous through the joint and is spliced
near column mid-height.   One of the challenges in research and design
has been to develop simple yet effective details to transfer large
shears and moments between the beams and columns.

 

 

Figure 2.  Connection between Steel Beam and Reinforced Concrete Column

 

Tests have demonstrated that composite connection details of the type
shown in Fig. 2 can provide excellent strength and deformation capacity.
For example, plotted in Fig. 3 are load-deflection curves of two
composite beam-column subassemblies that exhibit stable hysteretic
behavior (Kanno and Deierlein 1998).   The plot in Fig. 3a is for a test
where inelastic effects are confined to steel beam hinging outside the
column, and the one in Fig. 3b is for a case where the beam is oversized
and remains elastic with all inelastic deformations occurring in the
joint.   While the behavior shown in Fig. 3a (beam hinging) is preferred
for seismic design, the stable response in Fig. 3b demonstrates the
inherent robustness of these connections, even when the beam is stronger
than the joint.   Design guidelines for the connections are available
(ASCE 1994, AIJ 1994) that incorporate force-transfer mechanisms similar
to those commonly employed for reinforced concrete and/or steel
connections 

 ******************************************


-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu] 
Sent: Friday, June 30, 2006 7:14 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Moment Connections

Refugio:

There has been testing on this type of connection done.  In general, the
testing has resulted in three basic mechanisms that I am aware of...

1) Face plates and "butt" plate (or two sets of face plates if the
connection is two sided) are added to the steel beam.  The "face plates"
basically look like full height stiffners and are used on the face of
the
column where the beam comes into the column and generally are the same
width as the flange of the beam.  A "butt" plate (my term) is bascially
like a cap plate that is welded to the end of the beam and coinsides
with
the back face of the column (this assumes a one sided beam connection).
These sets of plates on either face of the column plus the flanges of
hte
beam create a nice confined space within the width of the steel beam.
Within that width, compression struts will form in the concrete when the
connection is loaded with a moment.

2) Stirrups in a close spacing are used above and below the connection
to
create a compression strut system (with the stirrups being the tension
ties) that works within the concrete that is outside of the width of the
steel beam.

3) Shear in the beam web helps as the last mechanism to resist the
moment
(kind of sharing load with mechanism #1).

I will note that this type of system generally has a steel erection
column
embedded within the concrete column (i.e. a steel column that is strong
enough to resist maybe a couple floors of construction dead load, but
not
all the final load of a high rise).

And I will note that this research was for situations where the concrete
column was wider than the steel beam (generally close to twice as wide),
which appears to NOT be the case for your situation.

If you want to look up paper, then authors have been Jim Wight & Gustavo
Parra-Montesinos of U of Michigan (Gustavo took over the research that I
was doing as a PhD student with Jim Wight when I decided a PhD was not
for
me).  I don't recall the other researchers at the moment, but I know
that
some was done at Texas A&M, I believe.  If you want, then I can find out
the other sources.

Regards,

Scott
Adrian, MI


On Thu, 29 Jun 2006, refugio rochin wrote:

> Anyone have experience with Steel Beam to Concrete Moment Connections
?
> I have a W21x166 coming into a Concrete Column 12x32".  The Beam
enters the
> 12" side.
> So the beam sticks out past the sides of the column a bit.
>
> So I am trying to come up with a best way to detail this connection.
>
> 1)  I bring the beam into the column, embedded inside the column, and
> provide long dowels through both beam flanges vertically, then
restrain the
> whole system with lots of ties.  Also to contain the temperature and
> Shrinkage stresses.
>
> 2) the argument against the #1 connection, is that the difference in
> concrete and steel materials will cause alot of cracking in the
concrete.
> So the second idea is to use a huge plate, at the face of the column,
weld
> the column to the plate, and then use anchors into the column to
restrain
> the moments, spreading the load a bit farther apart.
>
> I see advantages to both systems.  The first system takes into it, the
> compression from the wall continuing above, and removes any possible
shear
> at an exterior face, bringing it vertically into the column.  Whereas
the
> second system is able to spread the load.
>
> Personally I feel more comfortable with the first system, but I would
like
> some suggestions or comments from experience.
>
> Best Regards,
> Refugio Rochin
>

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