Table 94 in Sec . 3.2.3 , and Table 88 in Sec . 3.2.4 provides a summary of development and splice lengths for a range of concrete strengths for HIT-HY 200 V3 and HIT-RE 500 V3 according to CSA provisions for the specific case where the confinement term ( d cs
+ K tr ) has been taken as the maximum value of 2.5d b
. Refer to Chapter 6 of the Post- Installed Reinforcing Bar Guide and ESRs for additional design information relating to development length and lap splices .
Design example — development lengths for negative reinforcement slab extension
Requirement : Establish the embedment for post-installed reinforcing bars for a slab extension as shown in the figure below .
12-in .
12-in . ( E ) Slab ( N ) Slab
A
# 6 bars ( E )
≤ min ( 6-in ., ld / 5 ) B-B
8-in . 1.5-in .
Splice length
( E ) slab
New-to-existing slab connection Step 1 : Parameters
B
B
2-in .
A-A
PLAN
Roughened surface , 1 / 4-in . amplitude
A
# 6 bars ( N ) installed with Hilti HIT-RE 500 V3 adhesive
( N ) Slab
Roughened surface , 1 / 4-in . amplitude
SECTION
Existing construction ( E ) slab , 8-inch thick , 4000 psi normal weight concrete , Gr . 60 reinforcement , # 6 bars at 12-inch on-center spacing . Note : other detailing not shown .
New construction
( N ) slab , 8-inch thick , 5000 psi normal weight concrete , Gr . 60 reinforcement , # 6 bars at 12-inch on-center spacing .
Step 2 : Determine the development length for a Class B splice
Assuming K tr is equal to zero ( i . e ., no transverse reinforcing present to restrain splitting ), with 12−inch spacing and 1.5−inch cover , c b
= ( 1.5 + 0.625 / 2 ) = 1.875 inches and
( c b
+ K tr )/ d b
= ( 1.875 + 0 )/ 0.625 = 2.5 . With ( c b
+ K tr )/ d b
≥ 2.5 and less than 12 inches of concrete in the slab member installed below existing bars , Table 89 in Sec . 3.2.4 , applies to both existing and new reinforcement . From Table 83 in Sec . 3.2.4 , the Class B splice length of a # 6 bar in 4000 psi concrete is 22 inches .
Per ACI 318 25.5.1.3 , the distance between a post-installed reinforcing bar and an existing cast-in-place reinforcing bar to which the post-installed bar is spliced shall be no greater than the lesser of 6 in . and one-fifth of the development length . For this example 22 / 5 = 4.5 in .
Step 3 : Specification
Install # 6 Gr . 60 reinforcing bars at 12 inches on center with a minimum 24-inch embedment ( 22-inch splice plus 2-inch end cover ) using Hilti HIT-RE 500 V3 as shown in the figure above . Locate post-installed bars within 4-1 / 2 in . of existing bars to be spliced . Install in accordance with Hilti Instructions for Use . Do not damage existing reinforcing . Roughen interface to 1 / 4-inch amplitude prior to placement of post-installed bars .
Note : ACI 318 and ICC Evaluation Service Reports refer to the manufacturer instructions for use as the Manufacturer ' s Published Installation Instructions ( MPII ).
DEVELOPMENT OF POST-INSTALLED REINFORCING BARS BASED ON ACI 318 CHAPTER 17 AND CSA A23.3 ANNEX D ANCHORAGE PROVISIONS
ACI 318 Chapter 17 and CSA A23.3 Annex D contain design provisions for the determination of the tensile strength of post-installed adhesive anchors in concrete , whereby the strength is taken as the minimum of the resistances corresponding to steel rupture , concrete breakout , and bond failure at the adhesive-to-concrete interface . Since the establishment of development length is based on the assumption of the attainment of a minimum strength corresponding to yield of the bar , the design equations for anchorage can also be applied to this problem . Within the May- June 2013 issue of the ACI Structural Journal , “ Recommended Procedures for Development and Splicing of Post-Installed Bonded Reinforcing Bars in Concrete Structures ” by Charney , Pal and Silva provides a methodology for establishing the bar embedment to develop the bar using the concepts of anchorage contained in ACI 318 Chapter 17 . This methodology is similarly applicable to CSA A23.3 Annex D .
Note : This procedure is not addressed in ACI 318 or in CSA A23.3 . As stated in Charney , et al ., the assumptions made to ensure bar yield are a matter of judgment and may require unique determination for specific applications and conditions . For specific cases , contact Hilti .
The use of bond values corresponding to the assumption of uncracked vs . cracked concrete for the design of reinforcing bar embedment is a matter of judgment . The ACI 318 Chapter 25 development length provisions do not explicitly consider reduction of bond corresponding to cracking of the concrete that may arise in conjunction with structure loading , shrinkage , etc . Furthermore , while the development length provisions of the code appear to consider only the nominal yield strength of the bar , it may be prudent to provide sufficient embedment to develop the actual bar yield , generally assumed to be 125 % of the nominal value . Tables 90 and 95 in Sec . 3.2.3 , and Tables 84 and 89 in Sec . 3.2.4 provide calculated embedments to develop Gr . 60 rebar based on the application of anchor
26 Anchor Fastening Technical Guide Edition 22 | 3.0 ANCHORING SYSTEMS | 3.1 ANCHOR PRINCIPLES AND DESIGN Hilti , Inc . 1-800-879-8000 | en español 1-800-879-5000 | www . hilti . com | Hilti ( Canada ) Corporation | www . hilti . ca | 1-800-363-4458