Updates for beam-column joints reinforced with high-strengthreinforcement

Hung-Jen LeeAssociate Professor

National Yunlin University of Science and Technology

Advantages20-story case

Moment-resisting frame joints

Interior joint

Exterior joint

Nominal joint shear strength Joint confinementDevelopment and Anchorage

Beam-column joint tests at NCREE

13 14

15 16

Steel bar stress

fs = αo fyfs'

hc

Excessive slip

db

Crushed concrete

Crushed concrete Q

θ

Typical cyclic loading response

Very pinched hysteresis loops

Very low stiffness at small drift

Degraded strength in repeated cycles

fs = αo fyfs'= καo fy

hc

db =Beam bar diameterAverage bond focres

Steel bar stress

fs = αo fyfs'= καo fy

Can HSR be properly anchored in the joint？

Design Criteria for Minimum Joint Depth ACI 318-14

20≥b

c

dh

⋅≥

MPa420 20 y

b

c fdh

ACI 352-02 26 420

55020 =

⋅≥

b

c

dh

33 420

69020 =

⋅≥

b

c

dh

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′MPa =

𝑓𝑓𝑦𝑦38.4 𝑓𝑓𝑐𝑐′

psi

We proposed

0 2 4 6 8 10 12 14Concrete compressive strength, fc

' (ksi)

0.50

0.75

1.00

1.25

1.50

1.75

2.00

Re l

a tiv

e min

. colu

mn di

men

s ion

0 10 20 30 40 50 60 70 80 90 100Concrete compressive strength, fc

' (MPa)

10

15

20

25

30

35

40

13

20

26

33

39

46

52

16

25

33

41

49

57

66

Brooke and Ingham

(2013)

Li and

Leong

(2014)

Eurocode (2004)

NZS 3101

(2006)

AIJ Guideline (1999)

ACI 352R

(2002)

hc

db

420

550

690 MPa

Steel Grade

Steel

Grade

60

80

100 ksi

As,bot / As,top=

0.75P

= 0.2Ag

fc'

Proposed

Design Criteria for Minimum Joint Depth

Q

θ

Evaluation of hysteresis loop at the 2nd or 3rd cycle of 4% drift ratio

Energy dissipation

𝑄𝑄 ≥ 0.75𝑄𝑄𝑚𝑚

𝐾𝐾𝑜𝑜 ≥ 0.05𝐾𝐾𝑖𝑖

⁄𝐸𝐸𝐷𝐷 𝐸𝐸𝑃𝑃𝑃𝑃 ≥ 0.125

ACI 374.1-05Strength

Stiffness 𝐾𝐾𝑖𝑖 𝑄𝑄𝑚𝑚

𝐸𝐸𝐷𝐷

𝐸𝐸𝑃𝑃𝑃𝑃

20 30 40 50 60 70 80 90 100 110 120Concrete

compressive strength, fc' (MPa)

10

15

20

25

30

35

40

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

Beam-Column Joints with Grade 490 beam bars

23 420

49020 =

⋅≥

b

c

dh

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′

26 data

20 40 60 80 100 120 140 160Concrete

compressive strength, fc' (MPa)

10

15

20

25

30

Beam-Column Joints with Grade 590 beam bars

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

28 420

59020 =

⋅≥

b

c

dh

13 data

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′

Beam-Column Joints with Grade 690 beam bars 15 data

20 40 60 80 100 120 140 160 180 200Concrete

compressive strength, fc' (MPa)

10

15

20

25

30

35

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

33 420

69020 =

⋅≥

b

c

dh

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′

Seismic Testing for Interior Beam-Column Joints, Lee et al. (2014) A24

𝐴𝐴𝑠𝑠,𝑏𝑏𝑜𝑜𝑏𝑏

𝐴𝐴𝑠𝑠,𝑏𝑏𝑜𝑜𝑡𝑡= 0.75

24 mm 25mm 600

==b

c

dh

𝑓𝑓𝑐𝑐′ = 100 𝑀𝑀𝑀𝑀𝑀𝑀𝑓𝑓𝑦𝑦 = 690 𝑀𝑀𝑀𝑀𝑀𝑀

Test results

Qn

-918kN

918kN

-8 -6 -4 -2 0 2 4 6 8

Story Drift

(%)

-1500

-1200

-900

-600

-300

0

300

600

900

1200

1500

Sto

r y S

hear

, Q (k

N)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Q/ Q

n3 2 1

1 2 3

μ

μBJ-typeA24

33

𝑓𝑓𝑐𝑐′ = 100(116) 𝑀𝑀𝑀𝑀𝑀𝑀

𝑓𝑓𝑦𝑦 = 690(725) 𝑀𝑀𝑀𝑀𝑀𝑀

𝑀𝑀 = 0.05𝐴𝐴𝑔𝑔𝑓𝑓𝑐𝑐′

𝛼𝛼𝑜𝑜 = 1.15

Simplified equation

24 mm 25mm 600

==b

c

dh

Provided

4%-drift cycle Performance Rating = 3 Acceptable 𝐴𝐴𝑠𝑠,𝑏𝑏𝑜𝑜𝑏𝑏

𝐴𝐴𝑠𝑠,𝑏𝑏𝑜𝑜𝑡𝑡= 0.75

0.93, =n

mjh

VV

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

≥690

3.2 100= 22

30 40 50 60 70 80 90 100 110 120Concrete

compressive strength, fc'

(MPa)

15

20

25

30

35

Min

imum

Co l

umn D

e pt h

, h c (d

b)

420 560 700 840 980 1120Concrete

compressive strength, fc

(kgf/cm2)

ℎ𝑐𝑐 ≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′𝑑𝑑𝑏𝑏 𝑀𝑀𝑎𝑎𝑑𝑑 20𝑑𝑑𝑏𝑏

Thanks for your attention

-6 -4 -2 0 2 4 6

Drift Ratio

, θ (%)

-400

-300

-200

-100

0

100

200

300

400

Stor

y Shea

r , Q

(kN

)Brooke-2006Unit-3B

Bond or anchorage failure (BJa failure)

Brooke, N. J.; Megget, L. M.; and Ingham, J. M., (2006) "Bond Performance of Interior Beam-Column Joints with High-Strength Reinforcement," ACI Structural Journal, V. 103, No. 4, Jul-Aug,

Beam hinging but no bar buckling

Unit 3B

Robust hysteresis behavior

-6 -4 -2 0 2 4 6

Drift Ratio

, θ (%)

-400

-300

-200

-100

0

100

200

300

400

Stor

y Shea

r , Q

(kN

)Brooke-2006Unit-3B 2725/675/

537/45/0.75/,

==

=′

=

bc

yac

nmjh

dhff

VV

Bond failure at 4.4% drift ratio

Bond or anchorage failure along beam bars in the joint (BJa failure)

Hwang H-J, Park H-G, Choi W-S, et al. (2014) Cyclic Loading Test for Beam-Column Connections with 600 MPa (87 ksi) Beam Flexural Reinforcing Bars. ACI Structural Journal 111 (4)

Pinching behavior

Low residual stiffness at small displacement

Unlikely to repair

2225/055/635/30/

0.79/,

==

=′

=

bc

yac

nmjh

dhff

VV

Concrete crushing at beam ends

-250

-200

-150

-100

-500

50100150200250

Stor

y Shea

r, Q

(kN

)

-6 -4 -2 0 2 4 6Story

Drift Ratio

(%)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Q / Q

y

(d) Specimen

EW0

BJa-failure

-600

-450

-300

-1500

150300450600

Stor

y Shea

r, Q

(kN

)

-6 -4 -2 0 2 4 6Story

Drift Ratio

(%)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Q / Q

y

(c) Specimen

B1BJ-failure

“BJ” failure versus “BJa” failure

2025/005/470/56/

08.1/,

==

=′

=

bc

yac

nmjh

dhff

VV

2019/004/347/31/

78.0/,

==

=′

=

bc

yac

nmjh

dhff

VV

06.0/ =′cg fAP 10.0/ =′cg fAP

Lee et al. (2017) Lee et al. (2007)

Concluding remarks

G.L

Plastic Hinge

chbd

Pinching effect

Strength and stiffness degradation, poor hysteresis behavior

Low residual stiffness at small displacement

Unlikely to repair

Bond failure

ℎ𝑐𝑐 ≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′𝑑𝑑𝑏𝑏 𝑀𝑀𝑎𝑎𝑑𝑑 20𝑑𝑑𝑏𝑏

SD685-D25 Bar tensile tests

20

Grade, Size

Yield Strength(N/mm2)

Tensile Strength(N/mm2)

Elongation(%) TS/YS Yield

Pleatau

Criteria 685~785 ≧860 ≧10 ≧1.25 ≧0.014

SD685,D25 703 907 16 1.29 0.022

SD685,D25(Retest) 713 932 15 1.31 0.0216

SD685 D25Tensile tests0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

Strain

0

150

300

450

600

750

900

1050St

ress

(N/m

m2 )

D25-SD685

fya=703 N/mm2

fya=713 N/mm2

fua=907 N/mm2

fua=932 N/mm2

0 0.005 0.01 0.015 0.02Strain

0

150

300

450

600

750

900

1050

Stre

ss (N

/mm

2 )

E=223,369 N/mm2

E=196,481 N/mm2

Beam-Column Joints with Grade 420 beam bars

15 data

20 30 40 50 60 70Concrete

compressive strength, fc' (MPa)

10

15

20

25

30

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

ℎ𝑐𝑐𝑑𝑑𝑏𝑏

≥𝑓𝑓𝑦𝑦

3.2 𝑓𝑓𝑐𝑐′