# Product Technical Guides : US-EN Post-Installed Rebar Guide - Page 34

Post-Installed Reinforcing Bar Guide
6.0 WHAT ’ S THE BACK STORY ?
Example : Column structural joint ( compare with example provided in 2.6.4 )
Requirement : Establish the embedment requirement for postinstalled structural joint for a new column to be cast on an existing grade beam 15-in . wide by 30-in . deep with 4 ksi concrete and A615 Gr . 60 reinforcing . The new column is 15 x 15-inch square with ASTM A615 Gr . 60 # 7 column bars ( see Figure 17 ). The column must resist moment and shear arising from wind loading . d 1
T
Note : Additional checks for the adequacy of the model may be required . For further information , see Hamad , B ., et al . " Evaluation of Bond Strength of Bonded-In or Post- Installed Reinforcement ," ACI Structural Journal V . 103 , No . 2 , pp . 207-218 [ 8 ].
6.7 DESIGN OF SHEAR DOWELS
According to shear friction theory as adopted by ACI 318 , reinforcing bars that cross a shear plane serve to clamp the two faces of the shear interface together , enabling shear transfer through friction acting over the interface surface area . Although often referred to as dowels , the reinforcing bars that cross the shear interface are not assumed to resist shear forces through dowel action ; shear friction presumes that the reinforcing acts in tension only .
 z 1R st EQ EQ N s = T / sin w s so - SN N
 s c
w z 0 d b c
 Detail so - SN A c N Figure 51 — Strut-and-tie model for column to grade beam connection .
Determine the bond length based on the geometry of the compression strut required to develop the bar ( see Figure 51 ):
N s
=
T sinθ
T = ϕ ‧ A s ‧ f y
= 0.9 x 2 x 0.60 x 60000 = 64800 lbs f ce
= 0.85 x β s x β c x f ' c
= 0.85 x 0.75 x 1.0 x 4000 = 2550 psi ACI 318-19 Section 23.4.3 ϕ c
= 0.65 Assume a strut angle θ of 60 degrees :
N s
60000
W s
= = = 3.0 t x ϕ c x f ce 15 x 0.65 x 2040 x sin60 0 l st
=
W s cos60 0
= 6.0 in
Hanson , 1960 Matlock , 1976 Vesa , 1978 Bass et al ., 1989
Figure 52 — The main mechanisms of shear transfer along a reinforced concrete interface : dowel action and aggregate interlock , from [ 21 ].
However , recent work by Palieraki , et al . [ 16 ] has demonstrated that the static and cyclic strengths of the shear friction interface can accurately be described as the sum of friction and dowel action mechanisms . This approach also permits the determination of shear force transfer for reduced dowel embedment depths .
Mishima et al ., 1995 Soudki et al ., 1995 Mounir Kamel , 1996 Soudki et al ., 1996 Randl , 1997 Choi et al ., 1999 Choi et al ., 1999 ( 2 ) Valluvan et al ., 1999 Kono & Tanaka , 2000 Kono et al ., 2001 Kahn & Mitchell , 2002 Papanicolaou & Triantafillou , 2002 Nakano & Matsuzaki , 2004 Saari et al ., 2004 Banta , 2005 Dimitriadou et al ., 2005
Menkulasi & Roberts-Wollmann , 2005 Wallerfeisz , 2006 Hattori & Yamamoto , 2007 Scott , 2010 Wang et al ., 2010 Harries et al ., 2012 Shirai et al ., 2012 Palieraki , 2014 Shaw & Sneed , 2014 Mazizah & Izni , 2015 Alkatan , 2016 Sneed et al ., 2016 Trost , 2016 Xiao et al ., 2016 Palieraki et al ., 2017 Williams et al ., 2017 Costa et al ., 2018 Palieraki et al ., 2019 Virtzileou et al ., 2020
T u , exp
( psi )
T u , equ ( 1 )
( N / mm 2 ) 0 5 10 15 20
2900 20
2175
1450
725
 0 0 0 725 1450 2175 2900 T u , equ ( 1 ) ( psi )
15
10
5
T u , exp
( N / mm 2 ) l st l st
7.5 l d
= Z 0
+ = Z
2 1R x tanθ + ≈ 12 x tan60 + = 24 in . 2
2
Figure 53 — Prediction of static interface shear plotted against test results .
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