3 pre-stressed concrete, Pre-stressed concrete -6 – Campbell Scientific ST350 Strain Transducer for Structural Testing User Manual
Page 20
Section 5. Mounting of Sensor to Various Surfaces
-
When a transducer is attached to an extension it is significantly more
vulnerable to damage. A five gallon bucket is a good way to
transport multiple gages while extensions are installed. Put the
extension downward into the bucket and loop the cable over the
transducer to help prevent cable tangles.
5.2.3 Pre-stressed Concrete
1. Examples:
Bridges, building components (columns, joists, floor systems, etc),
foundations, piles.
2. Methods for attaching ST350:
a. Tab/ Glue: See above.
b. Threaded Studs: 1/4"-20 x 3-1/4” Powers Fasteners Power-Stud or
similar
-
Locate the gaging point on the structure
-
Using a concrete drill, drill 1/4” holes about 1.00” deep, ensure to
not drill into pre-stressing tendons.
-
Place two to three washers on the studs and thread on a bolt about
half way down the stud. These washers will act as spacers to
account for the height of the tab on the transducer end. Slide a
3/8” deep wall socket over the stud and hold it against the nut.
Pound in the stud by hitting the end of the socket; this will help
prevent bending the stud.
-
Tighten the washers against the concrete by twisting the nut with
an open end wrench. It is important to set the studs before
attaching the extension to prevent damaging the gage. Once
secure, leave the nut on the bolt to hold the washers in place.
-
Remove the washers and nut from the stud.
-
Slide the transducer end over studs.
-
While holding the transducer assembly in place, screw nuts on the
studs and tighten with an end wrench.
3. Installation method for best measurements:
Glue is sufficient for transducers that are only going to be installed for a
day or two. If the transducers are going to be left in place for an extended
period of time, threaded studs are required.
4. Pitfalls to avoid during installation:
-
Know the locations of the pre-stressing strands. Locate the drilled
holes between the strands to prevent damage to the strand.
5-6