Anchor Bolts Needed for this New Construction
Some of you may think we engineers lead lives of danger and excitement, similar to race car drivers or ace pilots. Well, in reality, there are times when we have really boring tasks to attend to, in addition to the adrenalin charged excitement of our normal day to day work. As an example, consider the 3 hours I spent recently watching a young contractor clean out some 3/4” diameter holes he had drilled into a concrete foundation, and then proceed to fill those holes with epoxy grout, and finally add the threaded rods (anchor bolts) to which he would later attach standard hold down hardware. On the ho-hum scale, this task is somewhere south of watching paint dry.
Joking aside, this sort of task is necessary, though mundane. Why, you ask? Some years ago, we began using embedded anchor bolts in this way as a way to resist tension uplift forces at the ends of certain walls we designated as “shear walls.” (This was in response to new building code provisions which required explicit design of all of the forces felt by individual shear walls. Prior to that, we simply added the useful wall lengths and divided by the total earthquake or wind force on the building – simpler times!) It was only a short while before we discovered that, if the drilled holes were not properly prepared, the dust which inevitably coated the insides of the holes drastically reduced the holding power of the epoxy. This meant that the rebar and epoxy could be pulled out of the holes like a popsicle, at a much lower load than we expected. So, without the inspections, we had no assurance that the shear walls and their anchor bolts would be able to resist the loads they are designed for.
I think every profession is cursed with such tasks, which are tedious, but oh, so necessary. Even race car drivers must be sure that all the parts are working – or at least the drivers still with us….
