Advantages of the System
The chemical epoxy anchoring system was chosen because of the following
distinct advantages it has over typical anchoring systems:
When an expansion anchor is used, the torquing required to fasten the
anchor introduces stress into the panel which may result in damage or
failure. The chemical anchor does not expand and therefore does not
produce this excessive stress in the concrete.
Placement of the chemical anchor is unaffected by wet conditions. It
may even be installed under water and the steel stud will not corrode
in the bore hole.
The epoxy bonds effectively in a diamond bit drilled hole and pullout
values of up to 55 kips (with dynamic invariance) may be obtained.
The above reasons combined with the fact that the installation of the
system is fast and simple (the epoxy components are guaranteed to be correctly
proportioned and will set in 30 minutes at 20C (68F)) made it desirable
over all other systems considered.
The advantages of this unique system also make it useful for other
applications. The resin cartridges were originally developed for use in mine
roof bolting. A mining company in Pennsylvania has found that by using the
chemical anchoring system, the time required for overcast construction in its
mine advancing operations was reduced. The resin-grouted anchor bolt is used
in combination with a spin-in bolt to assure horizontal control during
blasting and to eliminate the need for rebolting the mine roof after
blasting. Because of the strong bond developed between the bolt and the rock,
the roof bolts are insensitive to blasting damage which may ordinarily result
in the loss of bolt tension. Further, the chemical anchoring system does not
have the problems of anchor creep and rock breakage around the bearing plate
that mechanically anchored systems have.
The resin-grouted bolts may also be useful in anchoring the rails of
Overhead Electric Traveling (OET) Cranes. Typically, the crane rails are
supported by steel or concrete columns. However, an angle with stiffener
plates could be anchored to a spandrel beam to achieve the same result at a
lower cost (Figure 11). In situations where excessive crane loads would
require impractical bolting schemes, the anchors may be used in combination
with columns to substantially reduce the cost of the columns. This railing
system would be very reliable because of the anchor bolt's extremely high
pullout values and because it is unaffected by dynamic loading.
Underground steel fuel tanks subject to uplift due to hydrostatic pressure
can be anchored by using the chemical anchoring system. Holes may be drilled
through the bottom of the tank to grout the bolts into the concrete foundation
below (Fig. 12).