Post-Installed Reinforcing Bar Guide
2.0 HOW ARE THEY DESIGNED ? 2.1 DESIGN REQUIREMENTS
Design of post-installed reinforcing bar connections requires that the type , size , spacing and quantity be established for the connection . This is typically based on either direct calculation of section forces or a requirement to match existing reinforcement . Density and sizing of dowels for shear transfer between new overlays on existing structural elements such as slabs and walls may be based on other considerations .
Additional design considerations may include :
• loading type ( sustained , seismic , shock )
• fire requirements
• corrosion resistance
• detailing requirements based on element type ( integrity reinforcement , etc .)
2.2 JOBSITE CONSTRAINTS
Prior to designing a post-installed reinforcing bar connection , identification of the jobsite constraints is vital . Key parameters that should be accounted for in the design may include :
• existing reinforcement layout as given in drawings and confirmed on site using detection equipment ( see Section 3.1 ).
• required proximity of new to existing reinforcing to satisfy
• conditions for non-contact lap splices , etc .
• drilling method ( hammer drill , core drill , Hilti Hollow Drill Bit )
• orientation of connection ( downhole , overhead , etc .)
• ambient air and concrete temperatures at time of installation
• type and condition of the concrete e . g . cracked , carbonized
• access and geometrical constraints
2.3 REQUIRED BOND LENGTH
In general , the required bar embedment is based on the development length and splice provisions of the code 8 . Where geometrical or other practical constraints dictate , alternate procedures may be appropriate to establish bond length . The size of the bar and required bond length may also guide the type of adhesive system to be used . Adhesives with longer working time ( e . g ., Hilti HIT-RE 500 V3 ) are usually more appropriate for large diameter bars in combination with deep holes , whereby for small and medium bar diameters and shorter holes , systems with accelerated cure ( e . g ., Hilti hybrid adhesive HIT-HY 200 V3 ) can increase efficiency . These considerations may be affected by the anticipated job site conditions ( e . g ., access and ambient air and concrete temperatures ). project documentation . In addition , the specifications and details may include :
• adhesive system
• bar type and size
• required bar embedment
• hole diameters and drilling method ( s )
• requirements for preparation / roughening of existing concrete surface
• instruction on inviolability of existing reinforcement and embedded items as required
• requirements on training / certification of installers as required
• inspection / proof loading requirements
2.5 SYSTEM SPECIFICATION
Specifications should correlate to the design assumptions and the specific job site requirements addressed in the project documentation . Substitutions based on a simple specification of bond stress may not be sufficient to ensure proper execution of the work .
2.6 DESIGN EXAMPLES
The following design examples , based on the provisions of ACI 318-19 9 , are intended for illustration purposes only .
2.6.1 DESIGN EXAMPLE — SHEAR DOWEL
Requirement : Design dowels used to connect a new , unexposed 10-inch thick shotcrete ( pneumatically-placed ) shear wall to an existing concrete wall ( Figure 9 ).
( E ) wall
( N ) drilled-in dowels
( N ) shotcrete wall
2.4 CONNECTION DETAILING
The location of post-installed reinforcing bars with respect to existing reinforcement should be clearly indicated in the
8 ) See e . g ., ACI 318-19 25.4 & 25.5 . 9 ) Similar equations and procedures may be found in CSA A23.3-19 .
Figure 9 — Section through wall .