COMPREHENSIVE SERIES OF TESTS ON SEISMIC ... - PEER

peer.berkeley.edu

COMPREHENSIVE SERIES OF TESTS ON SEISMIC ... - PEER

COMPREHENSIVE SERIES OF TESTS ON SEISMIC PERFORMANCE OF

REINFORCED CONCRETE BEAM-COLUMN JOINTS


Background

• RC beam-column joint safety in seismic design

• joint shear strength design

• potential of joint shear resistance were evaluated by

lot of tests empirically

• specimens with beams and columns heavily

reinforced have been tested to assess the potential

• No comprehensive data set is available for actual

strength and post-yielding behavior of joints with

realistic range of reinforcement ratio in the beams and

the columns


Test Program

• Planed such that a dependable data set of RC interior

beam-column joint subassemblages should be obtained

• Lateral capacity and post yielding behavior are discussed

• Test parameters; including combinations of 3 factors

(1) amount of longitudinal reinforcement (3 levels)

(2) ratio of the flexural strength of the beams to the

flexural strength of the columns framing into a joint, (3

to 4 levels)

(3) ratio of the depth of the beam to the depth of the

column. (2 levels)


Conclusions

• Current seismic provisions for RC beam-column

joints are deficient, because they can not secure

the lateral strength of moment resisting frames

predicted by the flexural theory of RC sections

• Hence a large number of existing moment

resisting frame reinforced concrete structures

may be more vulnerable than we expect.

• Serious consideration on this test results should

be addressed by structural engineers,

researchers and code writers.


Loading Setup

Load cell

Oil Jack

Load cell

Specimens

Specimen A01

PC rod

Pin joint


Loading Setup



Load Cell

PC rod

Load Cell




Loading direction

Specimens

1/400

PC rod



3.0

2.0

1.0

0.0

-1.0

0.5Qc

-2.0

-3.0

1/200

1/100 2

1/50 2

1/33 2

1 2 3 4 5 6 7 8 9

Load Cycle


Strong floor


Loading Setup



Load Cell

PC rod

Load Cell




Loading direction

Specimens

1/400

PC rod



3.0

2.0

1.0

0.0

-1.0

0.5Qc

-2.0

-3.0

1/200

1/100 2

1/50 2

1/33 2

1 2 3 4 5 6 7 8 9

Load Cycle


Strong floor


Specimens

Loading point

700

Hoops or Stirrups

-D6@50 (SD295A)

240

Column

240

700

240

Column

240

700

Hoops or Stirrups

-D6@50 (SD295A)

340

Column

240

700

J oint Hoops

Two sets

-D6 (SD295A)

240

Beam

240

unit in mm

700 700

700

J oint Hoops

Two sets

-D6 (SD295A)

Beam

700

240 120

C01 C03

unit in mm

700 700

240

J oint Hoops

Two sets

-D6 (SD295A)

(a) Series B (b) Series C (c) Series D

170

700 700

Beam

240

unit in mm

11 4 11

in total 31 specimens in FY2008


Three Major Test Parameters

(1) Amount of longitudinal reinforcement,

p t

: 0.98% - 3.98%

(2) Ratio of the flexural strength of the beams to the

flexural strength of the columns framing into a joint,

M uc

M ub

: 72% - 268%

(3) ratio of the depth of the beam to the depth of

the column.

b b

b c

: 1.0 and 0.5


Common Parameters

• Normal strength deformed steel bars

• Concrete strength = 30 MPa

• Beam width and column width = 240 mm

• Joint shear reinforcement = 2 sets of D6

rectangular hoop

• Column axial load = 0 kN


Typical Test Result

80

60

40

Yielding of longitudinal bars in beams and columns

100

700

100 580

4-D13(SD345)

4-D13(SD345)

240

240

36 168 36

240

beams

&

columns

4-D13 SD345

pt=1.04%

4-D13 SD345

pt=1.04%

story shear kN

20

0

-20

240

-40

700

north beam

joint hoops

2sets -D6(SD295)

p w =0.32%

south beam

column hoops & stirrps

-D6@50(SD295)

-60

100

100

unit in mm

700 700 100

-80

-0.03 -0.02 -0.01 0.00 0.01 0.02 0.03

story drift ratio


Story shear-story drift relationships

100

100

150

100

Story shear , kN

75

50

25

0

-25

-50

-75

-100

100

-3.0

-2.0

-1.0

B01

0.0 1.0 2.0 3.0

75

50

25

0

-25

-50

-75

-100

100

-3.0

-2.0

-1.0

B02

0.0 1.0 2.0 3.0

100

50

0

-50

-100

-150

100

-3.0

-2.0

-1.0

B03

0.0 1.0 2.0 3.0

75

50

25

0

-25

-50

-75

-100

100

-3.0

-2.0

-1.0

B04

0.0 1.0 2.0 3.0

75

75

75

75

Story shear , kN

50

25

0

-25

-50

50

25

0

-25

-50

50

25

0

-25

-50

50

25

0

-25

-50

-75

-100

150

-3.0

-2.0

-1.0

B05

0.0 1.0 2.0 3.0

-75

-100

150

-3.0

-2.0

-1.0

B06

0.0 1.0 2.0 3.0

-75

-100

-3.0

-75

B07

B08

-100

-2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

100

100

Story shear , kN

50

0

-50

-100

-150

-3.0

-2.0

50

0

-50

-100

B09

B10

-150

-1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at face)

Yielding of longitudinal bar in column (at diatonal crack)

Maximum story shear

Series B

(a) Series A


Story shear-story drift relationships

Story shear , kN

100

75

50

25

0

-25

-50

-75

-100

100

-3.0

-2.0

-1.0

100

Longitudianal bar horizontal and

75

100

75

50

50

vertical, both of them

50

yielded in joints

25

25

0

0

0

-25

-50

-25

-50

-50

-100

-75

-75

B01

B02

B03

-100

-150

-100

0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0

100

100

100

150

100

-2.0

-1.0

B04

0.0 1.0 2.0 3.0

75

75

75

75

Story shear , kN

50

25

0

-25

-50

50

25

0

-25

-50

50

25

0

-25

-50

50

25

0

-25

-50

-75

-100

150

-3.0

-2.0

-1.0

B05

0.0 1.0 2.0 3.0

-75

-100

150

-3.0

-2.0

-1.0

B06

0.0 1.0 2.0 3.0

-75

-100

-3.0

-75

B07

B08

-100

-2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

100

100

Story shear , kN

50

0

-50

-100

-150

-3.0

-2.0

50

0

-50

-100

B09

B10

-150

-1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at face)

Yielding of longitudinal bar in column (at diatonal crack)

Maximum story shear

Series B

(a) Series A


Story shear-story drift relationships

Story shear , kN

Story shear , kN

100

75

50

25

0

-25

-50

-75

-100

100

75

50

25

0

-25

-50

-3.0

-2.0

-1.0

100

Longitudianal bar horizontal and

75

100

75

50

50

vertical, both of them

50

yielded in joints

25

25

0

0

0

-25

-50

-25

-50

-50

-100

Cracking

-75

B01

and crushing

B02

of concrete

-75

B03

-100

-150

-100

0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0

concentrated

100

in joints

100

100

75

75

75

50

50

50

25

25

25

0

0

0

-25

-25

-25

-50

-50

-50

150

100

-2.0

-1.0

B04

0.0 1.0 2.0 3.0

-75

-100

150

-3.0

-2.0

-1.0

B05

0.0 1.0 2.0 3.0

-75

-100

150

-3.0

-2.0

-1.0

B06

0.0 1.0 2.0 3.0

-75

-100

-3.0

-75

B07

B08

-100

-2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

100

100

Story shear , kN

50

0

-50

-100

-150

-3.0

-2.0

50

0

-50

-100

B09

B10

-150

-1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at face)

Yielding of longitudinal bar in column (at diatonal crack)

Maximum story shear

Series B

(a) Series A


Story shear-story drift relationships

Story shear , kN

Story shear , kN

100

75

50

25

0

-25

-50

-75

-100

100

75

50

25

0

-25

-50

-75

-100

150

100

-3.0

-3.0

-2.0

-2.0

-1.0

-1.0

100

Longitudianal bar horizontal and

75

100

75

50

50

vertical, both of them

50

yielded in joints

25

25

0

0

0

-25

-50

-25

-50

-50

-100

Cracking

-75

B01

and crushing

B02

of concrete

-75

B03

-100

-150

-100

0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

concentrated

100

in joints

100

100

75

75

75

50

50

50

150

25

25

25

B04

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

0

0

0

Maximum story shear observed were

-25

-25

-25

-50

-50

-50

smaller than flexural capacity of beam

-75

-75

-75

B05

B06

B07

B08

-100

-100

-100

0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

150

Story drift ratio , % Story drift ratio , %

or column in some specimens

100

100

Story shear , kN

50

0

-50

-100

-150

-3.0

-2.0

50

0

-50

-100

B09

B10

-150

-1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at face)

Yielding of longitudinal bar in column (at diatonal crack)

Maximum story shear

Series B

(a) Series A


Story shear-story drift relationships

Story shear , kN

Story shear , kN

100

75

50

25

0

-25

-50

-75

-100

100

75

50

25

0

-25

-50

-75

-100

150

100

-3.0

-3.0

-2.0

-2.0

-1.0

-1.0

100

Longitudianal bar horizontal and

75

100

75

50

50

vertical, both of them

50

yielded in joints

25

25

0

0

0

-25

-50

-25

-50

-50

-100

Cracking

-75

B01

and crushing

B02

of concrete

-75

B03

-100

-150

-100

0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

concentrated

100

in joints

100

100

75

75

75

50

50

50

150

25

25

25

B04

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

0

0

0

Maximum story shear observed were

-25

-25

-25

-50

-50

-50

smaller than flexural capacity of beam

-75

-75

-75

B05

B06

B07

B08

-100

-100

-100

0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

150

Story drift ratio , % Story drift ratio , %

or column in some specimens

100

100

Story shear , kN

50

0

-50

-100

-150

-3.0

-2.0

50

Legend :

Calcualted story shear at flexural capacity of beam

0

Yielding of joint hoop

Hysteresis behavior showed

Yielding

slip

of longitudinal

shape

bar in beam (at diagonal crack)

-50

Yielding of longitudinal bar in beam (at face)

Yielding of longitudinal bar in column (at diatonal crack)

commonly

-100

for all specimens

Maximum story shear

B09

B10

-150

-1.0 0.0 1.0 2.0 3.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Story drift ratio , % Story drift ratio , %

Series B

(a) Series A


Evaluation of Current Design Equations













Joint shear capacity

Flexural Strength

Tests


Evaluation of Current Design Equations













Joint shear capacity

Flexural Strength

Tests


Evaluation of Current Design Equations













Joint shear capacity

Flexural Strength

Tests


M uc M ub


1.0 1.5 1.3 1.2 1.0 1.4 1.8 1.0 1.0 1.0


Story shear-story drift relationships

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Specimen D01

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Specimen D02

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60


Specimen D03

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Specimen D04

80

60

40

20

0

-20

-40

-60

-80

Specimen D05

80

60

40

20

0

-20

-40

-60

-80

Specimen D06

Story shear , kN

80

60

40

20

0

-20

-40

-60

-80

-4 -3 -2 -1 0 1 2 3 4

Specimen D07

120

100

80

60

40

20

0

-20

-40

-60

-80

-100

-120

-4 -3 -2 -1 0 1 2 3 4

Specimen D08

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at column face)

Yielding of longitudinal bar in column (at diagonal crack)

Yielding of longitudinal bar in column (at beam face)

Maximum story shear

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , % Story drift ratio , %

(b)

Series DD


Story shear-story drift relationships

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Longitudianal bar horizontal and

60

60


50

50

40

40

vertical, both

30

of them yielded

30

in joints

20

20

10

10

0

0

-10

-10

-20

-20

-30

-30

-40

-40

Specimen D01

-50

Specimen D02

-50

-60

-60

Specimen D03

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Specimen D04

80

60

40

20

0

-20

-40

-60

-80

Specimen D05

80

60

40

20

0

-20

-40

-60

-80

Specimen D06

Story shear , kN

80

60

40

20

0

-20

-40

-60

-80

-4 -3 -2 -1 0 1 2 3 4

Specimen D07

120

100

80

60

40

20

0

-20

-40

-60

-80

-100

-120

-4 -3 -2 -1 0 1 2 3 4

Specimen D08

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at column face)

Yielding of longitudinal bar in column (at diagonal crack)

Yielding of longitudinal bar in column (at beam face)

Maximum story shear

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , % Story drift ratio , %

(b)

Series DD


Story shear-story drift relationships

Story shear , kN

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

Longitudianal bar horizontal and

60

60


50

50

40

40

vertical, both

30

of them yielded

30

in joints

20

20

10

10

0

0

-10

-10

-20

-20

-30

-30

-40

-40

Cracking

Specimen D01

and crushing of concrete

-50

Specimen D02

-50

-60

-60

Specimen D03

-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4

concentrated in joints

80

80

60

60

40

40

20

20

0

0

-20

-20

-40

-40

Specimen D05

Specimen D04

-60

-60

Specimen D06

-80

-80

Story shear , kN

80

60

40

20

0

-20

-40

-60

-80

-4 -3 -2 -1 0 1 2 3 4

Specimen D07

120

100

80

60

40

20

0

-20

-40

-60

-80

-100

-120

-4 -3 -2 -1 0 1 2 3 4

Specimen D08

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , %

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at column face)

Yielding of longitudinal bar in column (at diagonal crack)

Yielding of longitudinal bar in column (at beam face)

Maximum story shear

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , % Story drift ratio , %

(b)

Series DD


Story shear-story drift relationships

Story shear , kN

Story shear , kN

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

80

60

40

20

0

-20

-40

-60

-80

Longitudianal bar horizontal and

60

60


50

50

40

40

vertical, both

30

of them yielded

30

in joints

20

20

10

10

0

0

-10

-20

-30

-40

-40

Cracking

Specimen D01

and crushing of concrete

-50

Specimen D02

-50

-60

-60

Specimen D03

-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4

concentrated in joints

80

80

60

60

40

20

0

0

Maximum story shear observed were

-20

-20

-40

-40

Specimen D05

Specimen D06

smaller

Specimen D04

than

-60

flexural capacity

-60

of beam

-80

-80

-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4

or column in more specimens

Story drift ratio , %

120

100

80

Specimen D07

60

40

20

0

-20

-40

-60

-80

-100

-120

Specimen D08

-10

-20

-30

40

20

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at column face)

Yielding of longitudinal bar in column (at diagonal crack)

Yielding of longitudinal bar in column (at beam face)

Maximum story shear

-4 -3 -2 -1 0 1 2 3 4

-4 -3 -2 -1 0 1 2 3 4

Story drift ratio , % Story drift ratio , %

(b)

Series DD


Story shear-story drift relationships

Story shear , kN

Story shear , kN

Story shear , kN

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

80

60

40

20

0

-20

-40

-60

-80

Longitudianal bar horizontal and

60

60


50

50

40

40

vertical, both

30

of them yielded

30

in joints

20

20

10

10

0

0

-10

-20

-30

-40

-40

Cracking

Specimen D01

and crushing of concrete

-50

Specimen D02

-50

-60

-60

Specimen D03

-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4

concentrated in joints

80

80

60

60

40

20

0

0

Maximum story shear observed were

-20

-20

-40

-40

Specimen D05

Specimen D06

smaller

Specimen D04

than

-60

flexural capacity

-60

of beam

-80

-80

-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4

or column in more specimens

Story drift ratio , %

120

100

80

60

40

20

0

Hysteresis

-20

behavior showed slip shape

-40

-60

Specimen D07

-80

Specimen D08

commonly

-100

for all specimens

-120

-4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4

Story drift ratio , % Story drift ratio , %

-10

-20

-30

40

20

Legend :

Calcualted story shear at flexural capacity of beam

Yielding of joint hoop

Yielding of longitudinal bar in beam (at diagonal crack)

Yielding of longitudinal bar in beam (at column face)

Yielding of longitudinal bar in column (at diagonal crack)

Yielding of longitudinal bar in column (at beam face)

Maximum story shear

(b)

Series DD


Evaluation of Current Design Equations

150

Test+

Test-

Calculated (F)Flexural capacity of beam or column section

Calculated (S)Joint shear capacity : AIJ Guidelines)

Maximum attained story shear kN

125

100

75

50

25

Joint shear capacity

Flexural Strength

Tests

High Strength

Concrete

Specimens


0

D01 D02 D03 D04 D05 D06 D07 D08 D09 D10 D11 E01 E02 E03

Specimen (D-series and E-series)


Evaluation of Current Design Equations

150

Test+

Test-

Calculated (F)Flexural capacity of beam or column section

Calculated (S)Joint shear capacity : AIJ Guidelines)

Maximum attained story shear kN

125

100

75

50

25

Joint shear capacity

Flexural Strength

Tests

High Strength

Concrete

Specimens


0

D01 D02 D03 D04 D05 D06 D07 D08 D09 D10 D11 E01 E02 E03

Specimen (D-series and E-series)


Evaluation of Current Design Equations

150

Test+

Test-

Calculated (F)Flexural capacity of beam or column section

Calculated (S)Joint shear capacity : AIJ Guidelines)


Maximum attained story shear kN

125

100

Joint shear capacity

Flexural Strength

75

50

High Strength

Concrete

Tests

Specimens

25

M uc M ub 1.0 1.4 2.2 0.7 1.0 1.3 1.7 1.0 1.0 1.0 1.4 1.0 1.0 1.0

0

D01 D02 D03 D04 D05 D06 D07 D08 D09 D10 D11 E01 E02 E03

Specimen (D-series and E-series)


Mechanical Reinforcement Ratio and Strength

M uc M ub = 1.0

Nominal joint shear strength

Flexural strength of section

Normalized maximum moment* 1

0.30

0.25

0.20

0.15

0.10

0.05

M j

b b D b 2 f c

Calculated (F)

Series B

B03

B01 B02

Calculated (S)

0.00

0.0 0.1 0.2

Mechanical reinforcement ratio

0.3

a t f y

b b D b f c

Normalized maximum moment

0.40

0.30

0.20

0.10

0.00

0.0

M j

b b D b 2 f c

0.1

Series D

Calculated (F)

D01

0.2

D05

0.3

Mechanical reinforcement ratio

Calculated (S)

D08

0.4

a t f y

b b D b f c


Flexural Strengths Ratio

M j

bD 2 f c

Normalized moment* 3

0.20

0.15

0.10

0.05

B01

(Beam vs. Column)

B04

Calculated (F)

column

M uc

* 1 * 2

Series B

M ub

0.20

0.15

0.10

0.05

Calculated (F)

column

B02

B05

M uc

B06

Series B

M ub

Calculated (S)

Calculated (F)

beam

M j

bD 2 f c

Normalized moment

0.00

0.5

0.40

0.30

0.20

0.10

1.0 1.5

Flexural strength ratio

Series D

D02

D01

0.00

2.0 2.5 0.5 1.0 1.5 2.0

M* 1 uc M* 2

ub Flexural Strength ratio

Muc M ub

0.40

M ub

M uc

D03

0.30

0.20

0.10

D04

D05

D06

M uc

D07

Series D

M ub

2.5

Calculated (S)

Calculated (F)

beam

0.00

0.5

1.0

1.5

2.0

2.5

0.00

0.5

1.0

1.5

2.0

2.5

Flexural strength ratio

Flexural strength ratio

M uc M ub

M uc M ub


Summary of Test Results


Summary of Test Results

• Maximum story shear of some specimens are smaller 5% to

30% than the story shear calculated by the flexural strength

of the beam or the column


Summary of Test Results

• Maximum story shear of some specimens are smaller 5% to

30% than the story shear calculated by the flexural strength

of the beam or the column

• Those joints are conformed to current seismic provision, i.e.

they have safety margin of the nominal joint shear strength

by 0% to 50%.


Summary of Test Results

• Maximum story shear of some specimens are smaller 5% to

30% than the story shear calculated by the flexural strength

of the beam or the column

• Those joints are conformed to current seismic provision, i.e.

they have safety margin of the nominal joint shear strength

by 0% to 50%.

• The extent of insufficiency in the story shear is larger

a. if the flexural strength of the column is equal or nearer

to the flexural strength of the beam, and

b. if the depth of the column is larger than that of the

beam.


Modeling of yielding of longitudinal

bars in a beam-column joint

To understand the reason why the flexural theory overestimates strengths


Modeling of yielding of longitudinal

bars in a beam-column joint


loading start


corner cracking

corner cracking

corner cracking

story shear

story drift


diagonal cracking

diagonal cracking

story shear

story drift


crack opening

crack opening

story shear

story drift


load reversals

before

yielding

crack closing

story shear

story drift


crack opening

story shear

story drift


yielding

yield

yield

story shear

story drift


unloading

story shear

story drift


load reversals

after

yielding

crack remain due to residual stain after tensile yielding

residual crack remain

story shear

story drift


yielding

yield

yield


unloading

story shear

story drift


load reversals

after

yielding

story shear

story drift


slip

crack contact

crack contact

story shear

story drift

crack contact


ultimate

yield

yield

story shear

story drift


Definition of Ultimate Moment Capacity of Joint

yield

T

yield

C

C

j

yield

T

j


Proposed Equations for Ultimate Moment Capacity of Joint

(by Shiohara et al. : Nine Parameter Model)

O

T y

T y

B

F’

D

C

T y

T y

B

j 1

C

M j

gD D

ju O 1

M ju

j 1 = 1 2 D g − T y


D

C = T y



bDβ 3 ′

M ju = 2 j 1 T y = 2 j 1 C

f c




O

T y

T y

αT y

αT y

B

F’

D

M ju

T y

C 1

T y

B

j

C 1 = T y

C 2 = αT y

C 1

gD D

O

M ju

j 2 = 1

j 2

2 D (1− g) − C

j 2

1 = 1 2 D g − C 1


⎩ bDβ 3 f c ′

αT y

j 2

αT y

M ju = 2( j 1 T y + j 2 αT y ) = 2( j 1 C 1 + j 2 C 2 )

C

D

2

C 2

j 1

1








bDβ 3 f c ′




Prediction of Maximum Story Shear

(by New Model)





Test (+)

Test (-)

CalculatedUltimate moment capacity of joint

CalculatedMoment at balanced failure of joint


90


80








flexural strenth

Current

Maximum attained notal moment kN

70

60

50

40

30

20

10

moment capacity of joint

New Model


0


B01 B04 B07 B08 B02 B05 B06 B03 B09 B10


Specimens


Prediction of Maximum Story Shear

Test+

Test-

CalculatedFlexural capacity of beam or column section

CalculatedJoint shear capacity : AIJ Guidelines)

(by New Model)

150

125

Test (+)

Test (-)

CalculatedUltimate moment capacity of joint

CalculatedMoment at balanced failure of joint

150

Maximum attained story shear kN

125

100

75

50

25

flexural strenth

Current

Maximum attained notal moment kNm

100

75

50

25

moment capacity of joint

New Model

0

0

D01D02D03D04D05D06D07D08D09D10D11 E01 E02 E03

Specimen (D-series and E-series)

D01D02D03D04D05D06D07D08D09D10 D11 E01 E02 E03

Specimen


Conclusions

• Current seismic provisions for RC beamcolumn

joints are deficient and can not secure

the lateral strength of moment resisting frames

predicted by the flexural theory of RC sections.

• The design parameters considered is not a rare

feature but is rather seen frequently in existing

reinforced concrete buildings.

• Hence a large number of existing RC moment

resisting frame structures may be more

vulnerable than we expected.


Recommendation

• Serious consideration on the impacts of

this test dataset on huge stock of RC

building in the world should be addressed

by structural engineers, researchers and

code writers.


Let’s challange !


Bin Li (2009). Experimental and numerical Investigations on the Seismic Behavior of Lightly Reinforced Concrete

Beam-column Joint. Journal of Structural Engineering, ASCE, Sept. 2009.


Bin Li (2009). Experimental and numerical Investigations on the Seismic Behavior of Lightly Reinforced Concrete

Beam-column Joint. Journal of Structural Engineering, ASCE, Sept. 2009.


Acknowledgment

• The authors acknowledge the supports by the Grant-in-aid for researches

on the building codes improvement by Ministry of Land, Infrastructure,

Transport and Tourism, Japan, awarded to a research proposal entitled

“Research on design parameters of RC reinforced concrete beam-column

joint necessary for ductile behavior of building structures (PI: Hitoshi

Shiohara),” FY2008.


100

580

240

100

240

700

80

4-D13(SD345)

4-D13(SD345)

240

36 168 36

beams

&

columns

4-D13 SD345

pt=1.04%

4-D13 SD345

pt=1.04%

240

Yielding of longitudinal bars in beams and columns

700

100

60

joint hoops

2sets -D6(SD295)

p w =0.32%

40

north beam

south beam

column hoops & stirrps

-D6@50(SD295)

unit in mm

story shear kN

100

20

0

-20

-40

700 700 100

-60

-80

-0.03 -0.02 -0.01 0.00 0.01 0.02 0.03

story drift ratio


Observed Crack at 3% Story Drift


Observed Crack at 3% Story Drift

A

B

C

D

Story drift = 3%


Observed Crack at 3% Story Drift

A

B

A

B

C

D

C

D

Story drift = 3%

Story drift = - 3%


loading


loading


corner cracking

story shear

story drift


corner cracking

story shear

story drift


diagonal cracking

story shear

story drift


diagonal cracking

story shear

story drift


load reversals


load reversals


crack opening

story shear

story drift


crack opening

story shear

story drift


yielding

story shear

story drift


yielding

story shear

story drift


ultimate

story shear

story drift


ultimate

story shear

story drift

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