Bond requirements of straight beam bars passing through joints of special moment framesACI-ASCE Committee 352, "Recommendations for Design of Beam- Column Connections in Monolithic Reinforced Concrete Structures (ACI 352R-02)," American Concrete Institute, Farmington Hills, MI, 2002, pp. 38.
Key reference
50
100
150
200
250
Usage License by Story, Above 21 story buildings and floor area
Buildings Total floor areas (m²)
2016
Background
TaipeiTokyo
()
()
Advantages
20
Development length requirement at
failure at an interstory drift of 3%
for Grade 420 bars and a concrete
strength of 28 to 35 MPa.
Code background
Axial Load
6 m
3.2 m + +
32/600/
729/103/
30.1/,
“BJ” failure versus “BJa” failure
25/005/
470/56/
08.1/,
13
19/004/
347/31/
78.0/,
bc
yac
nmjh
dh
ff
VV
Bond failure along beam bars in beam- column joint (BJa failures)
14
G.L
Plastic
Hinge
ch
Unlikely to repair
T1= As,topao fy
T2= As,botao fy
Horizontal shear and bond forces acting on the joint concrete
jcjo AfV int
Design codes and standards
Yield strength, max (MPa)
420 550
420 550
540 675
390 490
Eurocode 8 (2004) All - - 1.20 NS 3101 (2006) (AS/NZS 4671:2001)
300E 500E
300 500
380 600
1.25
Factor accounting for the bar stress level developed in the joint
bp
yos
b
c
u
fα
d
h
a
a
4
Relative column dimension required by different codes and recommendations (1/2)
Relative column dimension required by different codes and recommendations (2/2)
Min. Col. Dimensions required by
different codes and recommendations
Design Criteria (MPa) 420 550 690 420 550 690
AIJ Guideline (1999) 29 37 44 18 23 28
Eurocode 8 (2004) 33 42 50 21 26 31
NZS 3101 (2006) 25 32 38 18 23 27
Brooke & Ingham (2013) 26 33 40 18 23 29
Li & Leong (2014) 28 35 43 20 25 31
Proposed Eq. 22 28 34 15 19 24
Kelly et al. (2014) 19 28 37 14 19 26
ACI 352R-02 20 26 33 20 26 33
Note: Reference beam-column joint with a column axial load of
0.2A ′; bottom-to-top reinforcement ratio of 0.75; equal diameters for
top and bottom bars.
y
b
c
f
f
d
h
(SI unit)
Kelly, D.; Lepage, A.; Mar, D.; Restrepo, J.; Sanders, J.; and Taylor, A., "Use of
High-Strength Reinforcement for Earthquake-Resistant Concrete Structures,"
Tenth US National Conference on Earthquake Engineering, Anchorage, Alaska,
2014.
Lee, H.-J., Chen, H.-C., Tsai, T.-C., (2016), “Minimum column depth for
acceptable bond performance of straight beam bars in beam-column joints,” The
18th Japan-Korea-Taiwan Joint Seminar on Earthquake Engineering for Building
Structures (SEEBUS 2016), Tainan, Taiwan, December 2-3, 2016.
RC
• 357 test data published in Japan, US, NZ, and Taiwan
• Unified database for normal-strength and high-strength RC
• Beam-column joints without trans. beams/slabs, eccentricity
Column bar versusyf cf
strength ratio for the 202 interior joints assembled
by Lee and Hwang (2013)
,
• Bar not less than 400 MPa
• A minimum of two cycles at the limiting drift ratio
• BJ or BJa failure
the limiting drift cycle(>3.5% 2nd or 3rd)
1

2 α =1.80 α = 1.56 α =1.83 α = 1.58 α = 1.87 α = 1.61
280 28 25 21 32 27 39 34 350 35 22 20 28 25 35 30 420 42 20 20 26 22 32 27 490 49 20 20 24 21 29 25 560 56 20 20 22 20 28 24 630 63 20 20 21 20 26 22 700 70 20 20 20 20 25 21 770 77 20 20 20 20 23 20 840 84 20 20 20 20 22 20 900 90 20 20 20 20 22 20
1000 100 20 20 20 20 21 20
0.15 ′
Column Joints 500x600-mm Beam 6-D32 top and bot.
600x600-mm Col. 16-D32
• Development Length
• Anchorage Length
≥ 0.192
≥ 0.06
′
(c)bar size ≤ No. 11 (D36);
(d)net bearing area of head ≥ 4;
(e)normal-weight concrete;
(g)minimum clear spacing of 3 between bars.
Conditions
Exterior Beam-column Joints
under Cyclic Loading
Specimen Design and Details ′ = 70 = 734 (690) = 843 (790)
Varying shear demands and Ash,ratio




• Development Length
• Anchorage Length
()
Required
• 615 cm
J o
in t
s h
e a
r fo
rc e
Deformation or Drift
ACI Code
′ 5.3 ′
′ 4.0 ′
′ 3.2 ′
= 0.083 ′
= 0.265 ′
Case study, bj and -value per ACI 318
• Beam width bb= 24 in. • Increasing square column section from 24x24 in. to 48x48 in.
Plan view of connectionBeyond x = 32x32,
< 0.75both values drop to 12
Trans. beam
Trans. beam
Interior joint Exterior joint
Tee joint Knee joint


3/4
Case study, proposed -value
• Beam width bb= 24 in. • Increasing square column section from 24x24 in. to 48x48 in.
,
< 0.75 value drop down one category Plan view of connection
Trans. beam
Trans. beam
b
x2
x1
12(6.3) 12 Τ 4[(2014)]
Effective Joint Area
6.1
6.2
6.3
(2016) NCREE-16-002
(2016)RC NCREE-16-010
(2016) NCREE-16-012
• Brooke, N. J.; and Ingham, J. M., "Seismic Design Criteria for Reinforcement Anchorages at
Interior RC Beam-Column Joints," Journal of Structural Engineering, V. 139, No. 11. 2013,
pp. 1895-1905.
• Kang, T. H. K.; Shin, M.; Mitra, N.; and Bonacci, J. F., "Seismic Design of Reinforced
Concrete Beam-Column Joints with Headed Bars," ACI Structural Journal, V. 106, No. 6,
Nov-Dec. 2009, pp. 868-877.
• Lee, H.-J.; and Hwang, S.-J., "High-strength concrete and reinforcing steel in beam-column
connections," Structures Congress 2013, Pittsburgh, PA, 2013, pp. 1606-1615.
• Watanabe, K.; Kiyohara, T.; Tasai, A.; and Hasegawa, Y., "Deformation Capacity of High
Strength RC Exterior Beam Column Joint with Beam Main Bars Anchored Mechanically,"
Proceedings of the Japan Concrete Institute, V. 26, No. 2. 2004, pp. 481-486.
(NCREE-16-002) 62
Column unit
Lb = 6 m
Lc = 3.2 m