CMU Partition Top Anchors - PTA 420

[abusementpark]

I have a project with a lot of CMU walls where connections will be made to the underside of concrete construction and vertical movement in the connection is desired. For various reasons, the connection needs to be entirely made on the top surface of the CMU wall, not the sides (e.g. sandwiching angles). I understand that the PTA 420 product linked below is commonly used for these applications.

For this product, do you simply leave the last course unreinforced/ungrouted and place the anchor in the 3/8" wide vertical mortar joints (32" on center) and just pack in mortar around it? It doesn't seem like the best connection for lateral resistance as you'd be relying solely on the bond strength of the mortar, but the force per anchor is pretty low for an interior partition or even an exterior wall in a low-wind zone

https://www.h-b.com/images/submittal/09PTA420ANCHR.pdf

 

[r13]

It seems the tube is placed over the steel rod/rebar in an un-grouted cell, then fully grout/pack around the tube to form the connection.

 

[abusementpark]

This image makes me think it is placed in the mortar joint between cells.

 

[abusementpark]

This one too, but you may be right.

How would you get grout in that cell? Knockout holes in the sides I assume?

 

[r13]

Your beam should be set after the device has placed in position. It is not any different then usual case - set beam bearing plate-grout the cell-place the beam. No conflict.

I see. Because the cells are covered by the compressible medium, only the vertical seam is the space available to install the sleeve. My mistake.

Note that the beam seems only sitting on the device, not rigidly attached, for interior partitions, the lateral load due to shear friction should be quite low then. The cells to receive the two plate fastening screws/bolts should be grout solid prior to installation then.

 

[BAretired]

Seems like it would be difficult to install. If the PTA 420 HS tube is grouted into the top course of masonry before placing the steel beam, it would not be easy to connect the plate to the steel beam so that the rod fit precisely into the tube.

Usually, steel beams are placed first, then masonry. In that case, the PTA device would be in place and the masons would have to work around it, having no clear access to place grout.

BA

 

[r13]

The beam has to be installed after the masonry. I suggest consider to alter the detail as follows: grout the cell solid, then drill a larger hole and epoxy the sleeve in position, then install the compressible medium and the hold-down plate-rod assembly. If the connection between the assembly and the beam is desirable, the beam flange shall have oversized holes matching the two holes on the hold-down plate, drill and grout bolts into the grout cell below. I doubt the necessity of the connection though.

 

[BAretired]

The device is intended to be used under either steel or concrete beams or slabs. Concrete would normally be poured before constructing masonry. The PTA device would need to be installed before completing the wall, so we are faced with the same problem for the mason. How does he place the grout?

BA

 

[r13]

If the beam has to come first, he has no choice but to use the vendor's detail - place in the brick slot. But I doubt it is desirable, as patching between the compressible medium and the beam could be challenging, or leave a gap. So the beam may have to come after the wall and the device.

 

[bones206]

PTA 420 HS - PTA Series Partition Top Anchors have been developed to provide lateral shear resistance at the upper limit of masonry walls.
They permit vertical deflection of the slab above, without transferring compressive loads to the masonry wall below. PTA Series Anchors are suitable for contruction using steel or concrete. PTA Tube with expansion filler is placed over rod anchor, which has been attached to concrete or steel by any of the methods illustrated. The vertical joint is then filled with mortar, fully surrounding the tube

https://www.h-b.com/images/submittal/09PTA420ANCHR.pdf

I've spoken with H-B's staff engineers before and they were helpful. They have a pretty good handle on means and methods contractors typically use with their products. Since they don't provide load ratings or testing reports for their products, my approach has been to designate these proprietary anchors as a delegated design item with a performance spec that the vendor/contractor has to meet and substantiate with documentation.

 

[BAretired]

It seems clear that the intent is to fasten the PTA 420 anchor to the steel or concrete beam first, before building the wall. Aligning them to occur precisely at a vertical joint would be difficult. Filling the joint with mortar, fully surrounding the tube is not possible without an access opening.

It seems more likely the anchors would be spaced at a modular distance apart, say 4'-0" o/c with the intent of hitting cores in the CMU. Access openings would be needed for grouting, marring the appearance of the wall surface.


BA

 

[bones206]

Something else to consider is the new infill wall seismic code requirements in TMS 402 Appendix B -- specifically the requirement that wall boundary connectors shall not transfer in-plane forces. I believe this is a paradigm shift that has not really made it's way into industry or common practice as of yet.

 

[BAretired]

Would 3/8" diameter rods fitting loosely in plastic tubes encased in mortar, bending through a neoprene sponge, be considered adequate lateral support for a masonry wall in a seismic event? Or even a strong wind?

BA

 

[bones206]

That's why I require the contractor or mfr to prove the lateral capacity is adequate via delegated design submittal. As far as I know they do not publish any generic capacity values. In past discussions with an H-B engineer, they indicated that they can engineer heavier-duty devices for high winds.

But that is for out-of-plane forces. The code requirement I noted above is that CMU infill walls must be unrestrained in the in-plane direction. I don't mean to stray too far off topic, but I just wanted to point that requirement out, since it prohibits the use of some of the proprietary systems currently on the market. I don't know if there is an "out" for allowing in-plane restraint, unless you are specifically in a non-seismic area like Florida.