Campbell Scientific ST350 Strain Transducer for Structural Testing - Manual (Page 17)

Section 5. Mounting of Sensor to Various Surfaces
5.2.2 Reinforced Concrete
See “Instructions for Using ST350 Strain Transducer
Extensions on Reinforced Concrete Structures” in Appendix A
for extension attachment instructions and important information
regarding the use of transducer extensions. NOTE
1. Examples:
Bridges, building components (columns, joists, floor systems, etc),
foundations, piles.
2. Methods for attaching the ST350 Strain Transducer to reinforced
concrete:
a. Tab/Glue: See above.
b. Tab/Glue + Threaded Stud (1/4"-20 x 3-1/4” Powers Fasteners Power-
Stud or similar)
- Locate the gauging point on the structure and make two marks
approximately 2 feet apart along the axis of where the
transducer/extension assembly is to be mounted. It can
sometimes be difficult to align the marks on the bottom of
concrete slab structures, particularly if the structure is skewed.
Often, a series of marks are laid out on the bottom of the slab and
a chalk line is used to lay out a grid, making gage alignment very
easy. Another alternative is to use a laser chalk line to
temporarily create a line while the gage is installed.
- Temporarily hold the transducer/extension assembly up to where
it is to be mounted to ensure that there are no obstructions along
the length of the unit. Make small marks at the two mounting
points, one for the transducer end and one for the selected gage
length on the extension end (6-24inches).
- Using a concrete drill, drill a 1/4” hole at the extension end mark
about 1.75” deep. For the tab end, it is possible that the concrete
surface will need to be smoothed slightly with a grinder to ensure
that the tab is making good contact with the structure. Once
smooth, use the edge of the grinder as a cutting wheel and cut two
or three grooves at a 45°
angle to the direction of gage. Be sure to
wipe all grinder dust clear from the location using a rag or paint
brush. If possible, use compressed air (available in cans) blow
the area clean.
- Place two to three washers on the stud and thread on a bolt about
1/2 of the way down its length. 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.
Drive the stud into the concrete by pounding on the end of the
socket; this will help prevent bending the stud.
5-3