Precured Shapes for
Near Surface Mounted (NSM) Application
Pre-cured NSM rod/shape
systems can generally be used as an alternative for reinforcing concrete
and masonry structures similar to surface laminates. NSM Rods/shapes
provide a more discrete solution to strengthening structures in that they
generally are inserted into the masonry or concrete structure via slot or
saw cuts. Generally, shapes can vary in size depending on application but
typically are provided in round and rectangular cross-sections. The shapes
are manufactured in the system supplier’s facility and shipped to the job
site. The shapes generally feature a surface treatment to facilitate bond
between the FRP and adhesive or grout. An epoxy adhesive or cementitious
grout is used to bond the precured rods in the groove cut into the surface
Adhesive selection is critical in that the adhesive provides for the
proper transfer of load between the wall and the cured reinforcement. A
cosmetic surface can then be added to completely hide the strengthening
system. Since the products are embedded into the substrate and bonded on
three sides of the FRP shape, development lengths for NSM strengthening
may be shorter. NSM rods/shapes may also be anchored into adjacent
members and the opportunity of upgrading elements in their negative moment
region is opened-up, as the FRP shape is not exposed to potential
mechanical damage typical of floor or deck systems. FRP rods/shapes using
the NSM technique does not require extensive surface preparation and
installation time may be less than other systems. The American Concrete
Institute Committee 440 is presently reviewing modifications to
ACI440.2R-02 to document design methodologies for FRP/NSM strengthening.
Installation/Application
After assessment of
the condition of the existing structure and design by a competent
professional, installation of the NSM FRP strengthening is performed
according to the following general guide:
-
Cut
Groove –
Using a diamond blade saw or grinder, a groove 1.5 times the bar diameter
(in the case of a rectangular FRP shape, 1.5 times the depth and 3 times
the thickness) is cut as prescribed. The use of two diamond blades on the
saw arbor may be necessary.
-
Prepare Groove –
The groove is masked
with masking tape or similar product to prevent excess adhesive from
marring the surface. The groove is thoroughly cleaned using a vacuum
and/or compressed air.
-
Apply Adhesive –
Structural adhesive
gel or grout is filled in the groove. Care should be taken to avoid
entrapped air voids.
-
Place FRP rod/shape Into Groove –
After the adhesive
has been applied into the groove, the rod is placed and pressed into the
groove to insure proper location of the rod/shape.
-
Finish –
After the FRP rod/shape is seated into the groove, the adhesive is
smoothed and any additional adhesive is added. General clean up and
removal of the masking.
QuickLink to Products
Edge Structural Composites, Inc.
Gordon Composites, Inc.
Hexcel Schwebel Civil Engineering and
Construction Systems, Inc.
Hughes Brothers, Inc.
Saint-Gobain Technical Fabrics
Sika Corporation
TechFab, LLC
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