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RE: Precast Column Base Connection

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            Mark,

                        I should have mentioned the provisions we take for foundation to precast Splice Sleeve connections to account for tolerance. There are four:

 

                        We use a sleeve that is two bar sizes larger than the bar, i. e., #11 sleeve for a #9 bar and a #14 sleeve for a #11 bar. And one probably could get a “#12 sleeve” for a #10 bar, as I understand they have a sleeve for a metric bar that is about what a #12 bar would be.

                        We provide the foundation dowel with a Wilson (used to be Sinco) sleeve around it. I used to have a favorites link for them, but I just tried it and it did not work. This allows a little horizontal adjustment, though a pretty big crowbar or a pretty big man is required to push a #11 around much. The annulus is grouted with the NMB Splice Sleeve.

                        We detail the foundation dowel to project 1’ to 2’ higher than is required, with the prescribed dimension for our survey crew to mark. Then our erection crew cuts to the mark and has a bar projecting the right height.

                        The foundation dowels are A 706 (weldable) material. This helps for bars cast too short despite being detailed overly tall.

 

                        We still end up suggesting to foundation contractors how to grout or epoxy bars in despite these steps. And I saw six bars in the end of a shear wall this summer with only part of their Wilson sleeves around them: the foundation had been poured too high, so it was chipped down and the Wilson sleeves cut off at the new (original design) top of foundation elevation. Now maybe you have an idea why our field crews do not like them. But we are not in a high seismic area like Jake. If we were, we would have done enough to make them work easily and the foundation contractors would have done enough to do them better.

 

                        When we have a lot of Splice Sleeves required in precast-to-precast joints in panels of the same shape, we will make steel formwork instead of wood so that the holes for the dowels do not enlarge when the panels are stripped each day.

 

                        And NMB understands that they have a product that is difficult to use. They have collected these stories and others from other people and provide them to their customers and they have made a bunch of tweaks a to their product over the years and provide or will tell you where to find parts that others make that can make life easier when using their products. I think that may be a run-on sentence. Erico is also helpful, but we have just gotten in the NMB habit, so I cannot speak to all of their help.

            Jim Getaz

            Winchester, Virginia