Structural Tie-Down Apparatus

Abstract

Top plate tie-down arrangements are used for securing the roof of a structure against uplift and overturning forces caused by high winds, earthquakes, and the like by anchoring the top plate of a wall to a foundation slab. An anchor bolt for use in a top plate tie-down arrangement has an internally threaded head for capturing the sill plate and holding it against the slab. The bolt also has a self-tapping thread on its bottom end that allows it to be threaded into a hole drilled through the sill plate and into the slab.

1 . A method of attaching a top plate of a wall to a slab disposed beneath the wall, the method comprising the steps of:
 a) providing a selected number of anchor bolts, each bolt extending from a respective tip to a respective head end, each bolt comprising an externally threaded portion extending from the respective tip towards the respective head end by an embedment length, each bolt having a respective internally threaded portion extending from the respective head end toward the respective tip by a coupling length, each bolt comprising a respective head at the head end thereof, each head having a plurality of drive facets;   b) drilling a selected number of holes into the slab, each of the holes extending into the slab by more than the embedment length;   c) inserting each of the selected number of anchor bolts through a respective throughhole in a sill plate and into a respective hole in the slab;   d) turning each anchor bolt, by means of a drive tool engaging the respective plurality of drive facets thereof until the sill plate is captured between the respective bolt head and the slab,   e) threadably connecting a lower end of each of the selected number of vertical tensile fasteners to the internally threaded portion of a respective bolt head, each of the vertical tensile fasteners comprising an attachment means adjacent an upper end thereof, each of the attachment means attaching the respective vertical tensile fastener to the top plate.   
     
     
         2 . The method of  claim 1  wherein each of the anchor bolts has an anchor bolt diameter and each hole extends into the slab by at least one anchor bolt diameter more than the embedment length. 
     
     
         3 . The method of  claim 1  wherein the sill is captured between the respective bolt head and the slab by means of a respective washer-like portion of the respective bolt head, the respective washer-like portion extending laterally outward from an axis of the respective bolt beyond the respective plurality of facets. 
     
     
         4 . A top plate tie down apparatus connecting a top plate of a wall to a concrete foundation, the wall extending upward from a sill plate disposed on the concrete foundation, the sill plate having a plurality of throughholes therethrough, the apparatus comprising:
 a selected number of anchors, each anchor having a respective portion threadably engaging the foundation beneath the wall along an embedment length, each anchor having a respective internally threaded upper portion, each of the anchors having a respective head at the upper end thereof, each head holding the sill plate against the slab;   the selected number of vertical tensile fasteners, each of the vertical tensile fasteners connected to the top plate, each of the vertical tensile fasteners further comprising a respective lower threaded portion at a respective lower end thereof, each of the lower threaded portions threaded into a respective internally threaded upper portion of a respective one of the anchors.   
     
     
         5 . The apparatus of  claim 4  wherein the length of each of the respective threaded portions of the vertical tensile fasteners is equal to a length of each of the internally threaded portions of the anchors. 
     
     
         6 . The apparatus of  claim 4  wherein the anchor threadably engages the foundation by means of a self-tapping lead thread comprising a helical land having a high helix angle, the lead thread further comprising a helical dust relief groove formed in a body of the anchor.