Shoring open web steel joists

[Ipetu]

There is a masonry wall that is 8.82 m high. At an elevation of 3.57 m measured from the floor elevation the masonry wall supports a series of OWSJ. The masonry wall is to be removed from the floor elevation to the underside of the joists. The joists are to be supported by a steel beam and column system. The masonry wall from elevation 3.57 m to 8.82 m is to remain in place. A photograph showing the wall to be removed and the supported OWSJ is attached. How can one temporarily shore the joists until the steel beam and columns are installed to permanently support the steel joists and the masonry wall above?

My first guess is bottom chord bearing a little ways away from the wall to be removed. However I have concerns about the dead load from the masonry wall that extends from elevation 3.57 m to 8.82 m. This will create a cantilever load on the overhanging joists.

 

[vandede427]

Cut loose the welds of the joist seat to the wall before you shore the joists.

 

[hokie66]

You need to support the wall, not the joists. The joists are supported by the wall. Don't even think about hanging the wall off the end of the joists.

 

[Ron]

Agree with hokie66...if you do as you propose, the first diagonal will buckle.

Assuming you have a tie beam beneath the joists, sawcut the masonry wall vertically, halfway between filled cells. Cut about a 12 to 16 inch width, from the beam down to the floor. Use a competent pipe shore with adjusting jack in the cut-out space. Do this one at a time for the length you want the wall removal to be. After shoring is in place on 3 or 4 foot centers, you can then remove the wall in between.

You might need to leave the tie beam in place and supplement it with a steel beam, but you'll have to carefully analyze the pipe shoring and tie beam to determine the best way to put a beam in place under the tie beam.

Unfortunately the joist shoe and the diagonals will not likely support the wall above for temporary shoring. You will likely have to beef up the diagonals and the top chord/shoe interface to accommodate any additional removal.

 

[DTGT2002]

Making up the concept here, but what if the mortar joint between two courses was sawcut out to some depth such that an angle suitable for serving a half the lintel or header could be installed as a seperate operation from either side.

Then proceed as noted by Ron, carefully removing a narrow width below the angles, tying the angles together with plates and welds as needed and installing appropriate columns.

One big question I would have is how will you provide and maintain lateral stability of the system, in construction and final use with the wall eliminated.



Best of luck.

Daniel

 

[FFENGINEER]

What about a beam above on the floor inside of the wall, supported each end, then some sort of saddle thru the floor to hang the joists why the wall is removed, a new beam put in place, then your shoring beam reomved. Thats if you have enough room to slide in a shoring beam on the second floor. this give you clear work area below, other than the two columms supporting the shoring beam.

 

[FFENGINEER]

Does the wall need to be cut above the joists? Can the existing wall hang down to the bottom of the bottom joist chord? this would allow you to sandwich the wall below the joists with some channels, and then cut the wall below the channels. The channels would support the wall, joists, etc.

 

[JAE]

I've done what FFENGINEER suggests.

You first cut vertical slots in the wall to allow installation of new tube columns - size to match the thickness of the wall.

Then, we install steel channels on either side of the wall, welded or bolted to the columns. The channels are though-bolted through the wall to each other. Keep in mind - the wall is still essentially in place at this point.

Next, begin demolishing small sections of the wall directly under the channel, perhaps 2 to 3 feet (600mm to 900mm) at a time - only 2 to 3 feet vertically as well.

As the masonry is removed, install horizontal steel plates under the channels, welded to the channel bottom flanges - this creates a "U" shaped lintel that carries the wall above.

As you progress along the spans, keep installing the plates.

Once all the wall under the channels is demolished, complete the demolition of the remaining wall below.

As others have suggested above - look out for lateral stability of the wall itself with the remaining portion of the structure.

 

[Ipetu]

FFENGINEER / JAE:

Would you be kind enough to provide a sketch to go with the explanation that JAE has posted. Also note that I have wide open access from both sides of the wall.

Thanks.

 

[BAretired]

The double channel idea seems to be the most practical way to do the job. The top of channels would need to be kept down far enough to clear the end diagonal of the joists.

BA

 

[hokie66]

JAE's way will work, but deflection could be a problem as load comes onto the channels.

The more traditional way is to needle through the wall, with the needles supported on shores. Then remove the masonry, install a steel beam on columns under the wall which can be prestressed with flat jacks to take up the dead load.

 

[paddingtongreen]

I agree with hokie. There is a case here for using full nuts as leveling nuts under the baseplate to snug the column tight to the beam.

It looks like we're back to arching.

Michael.
Timing has a lot to do with the outcome of a rain dance.