Note : Tables 90 and 95 in Sec . 3.2.3 , and Tables 84 and 89 in Sec . 3.2.4 provide suggested embedment depths , edge distances , and spacing values for the development of Grade 60 reinforcing bars . Bond strengths have not been reduced for seismic loading and a bar overstrength factor of 125 % of nominal yield has been applied in the determination of the values provided . Bond strengths include reductions for sustained tension loading as provided in the applicable evaluation reports ; however , no additional reduction in accordance with ACI 318 17.3.1.2 has been included . Where bars are used to resist sustained tension loading , increases in the tabulated embedment values may be appropriate . Consult Hilti Technical Services for further information .
Ca
( N ) drilled-in starter bars
( E ) Slab on grade
Condition I : thin member , light or no reinforcing
( N ) drilled-in starter bars
DEVELOPMENT OF POST-INSTALLED WALL / COLUMN STARTER BARS IN A LINEAR ARRAY BASED ON ACI 318 CHAPTER 17 AND CSA A23.3 ANNEX D ANCHORAGE PROVISIONS
Note : This procedure is not addressed in ACI 318 or in CSA A23.3 . For additional information see 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 . As addressed in this study , 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 .
In Tables 91 through 93 and 96 through 98 in Sec . 3.2.3 , and Tables 85 through 87 and 90 through 92 in Sec . 3.2.4 , the expressions presented in the study have been expanded to include the effects of set spacing of starter bars in a linear array at set spacings . To produce these tables A Nc is defined by ACI 318 , 17.4.2.1 and Fig . R17.4.2.1 ( CSA A23.3 D . 6.2.1 and Fig . D . 7 ). A Na is defined by ACI 318 , 17.4.5.1 and Fig . R17.4.5.1 ( CSA A23.3 D . 6.5.1 and Fig . D . 11 ). A Nco and A Nao are defined by Equations ( 17.4.2.1c ) and ( 17.4.5.1c ) ( CSA Equations ( D . 5 ) and ( D . 22 )), respectively . Inclusion of these terms permits the effects of edge distance to be considered on the concrete breakout and bond strengths . Using the relationships above , the equations below for h ef for both breakout and bond can be found , the larger of which is taken as the final embedment depth .
N steel , m
= n bars
A b
( 1.25 ƒ y )
( )
N breakout , m
= A Nc ф c k c , uncr ƒ ' c h ef , breakout
1.5
A Nco
Ca ( E ) mat foundation
N bond , m
= A Na ф b τ k , uncr πd b h ef , bond
ANao
whereby the concrete breakout and bond strengths with reduction factors applied are each set equal to the assumed bar yield strength and the resulting expressions are solved for
h ef as follows : As governed by multiple-bar breakout strength :
( ) h ef , breakout
= 1 A n A ( 1 . 25 ƒ ) 2 / 3
Nco bars b y
ф c
A Nc k c , uncr ƒ ' c
Condition II : thick member , heavily reinforcing Considerations for determination of minimum edge distance with minimum c a intended to preclude edge effects . Note : The term ( A Nco
/ A Nc ) depends on h ef .
For this reason , the calculation of h ef using the equation above may require iteration .
28 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