Nonlinear Finite Element Feng Xiong PhD Professor of Civil ...risedr.tongji.edu.cn/ubc/PPT/5.4/plenary 1/3 Feng XIONG-Nonlinear... · Feng Xiong PhD Professor of Civil ... Nonlinear

Feng Xiong PhD

Professor of Civil

Engineering

Sichuan University

Nonlinear Finite Element

Analysis for Precast Short

Column Connections Under

Cyclic Loading

Background and MotivationP03

Seismic Behavior Testing of Precast short columnsP04

Finite Element Analysis of Precast Short ColumnsP18

Comparing of Shear Strength Formulas of Precast Column Joint between Chinese and Japanese Codes

P37

ConclusionP39

CONTENTS

Background and Motivation

With the development of industrialized building, precast concrete

structures are currently applied since the advantages in low

costing, better quality, and quickly constructing;

The short columns with shear-span ratio less than 2.0 frequently

occur in high-rise precast concrete frame structures with

increasing of column section size;

The one concern in precast column design is the shear strength of

joints in the column bottom. Does the shear failure occur along the

joints when using wet connections, i.e. sleeve grouting connection?

In the new Chinese "Technical specification for precast concrete

structures”(JGJ 1-2014), a shear strength formula is first given. But

it is quite different from in Japanese codes

No Concrete pouring Rebar connecting Joint configuration

PSC-A-1 Cast-in-place No No joint

PSC-D-2 Cast-in-place Sleeve grouting No joint

PSC-E-3 Precast Sleeve grouting Joint with shear key

PSC-C-4 Precast Sleeve groutingJoint filled in grouting

material

PSC-B-6 Precast Sleeve grouting Joint filled in concrete

Two cast-in-place short columns and three precast short columns

were tested under cyclic loading to investigate the effects of sleeve

grouting connection and joint configurations on the behaviors of the

column。

Seismic Behavior Testing of Precast Short Columns

• Testing Objective

• Test specimens

Specimen PSC-A-1 Specimen PSC-D-2

Testing specimen elevations

Specimen PSC-E-3 Specimen PSC-C-4 Specimen PSC-B-6

Testing specimen elevations

（1）Concrete

No Concrete Age（day）Cube Strength

fcu（MPa）

Cuboid Strength

fc(MPa)

PSC-A-1

C45

42 45.24 34.39

PSC-D-2 55 46.26 35.16

PSC-E-3 31 50.07 38.06

PSC-C-4 48 45.89 34.88

PSC-B-6 35 51.08 38.82

Materials of testing specimen

（2）Steel rebar

Diameter

Yield

strength

fy(MPa)

Ultimate

strength

fst(MPa)

Elastic modulus

Es(MPa)Remarks

18(1) 432 615 191606In member PSC-D-2、PSC-E-3、

PSC-C-4、PSC-B-6

18(2) 517 657 202228 In member PSC-A-1

6 450 583 180304 Stirrups

Testing Equipment

Loading System

The design axial compression ratio of all testing specimens is 0.6.

The axial loads calculated as the measured concrete strength were

exerted as the table following；

Horizontal cyclic loading was controlled by the displacement as the

figure.

Specimen

Axial

Compression

Calculated

kN

Axial

Compression

Exerted

kN

PSC-A-1 1466 1466

PSC-D-2 1498 1498

PSC-E-3 1629 1460

PSC-C-4 1466 1466

PSC-B-6 1661 1460

Testing process and observation

• Horizontal bending cracks

occurred on the top；

• When loading at

displacement of±5.25m,

diagonal cracks occurred

in the cross shape；

• When getting to ultimate

loading, diagonal cracks

distributed in whole

column；

• When loading at

displacement of ±21mm

concrete began to crush；

• Finally loading at

displacement of±42mm,

concrete crushed and

rebar exposed，indicated

column damage.

Crack at

1.3125mm

Crack at

5.25mm

Crack at

10.5mm

to ultimate

loading

Crack at

42mm

when

damaging

Specimen PSC-A-1 (cast in place)

• Horizontal bending cracks

occurred on the top at

±1.3125mm, with the joint

at the bottom cracking；

• Similar process occurred

as the cast in place

specimen；

• Finally loading at

displacement of±42mm,

concrete crushed and

rebar exposed，but the

joint crack didn’t go

through.

Cracking

at 1.3125mm

Diagonal

cracks

occurred at

5.25mm

At 10.5mm

Got to ultimate

loading

At 42mm

Specimen

damaged

Specimen PSC-E-3 (Precast)

Testing process and observation

Hysteretic Curves

PSC-A-1 PSC-D-2 PSC-E-3

PSC-C-4 PSC-B-6 5 specimens

including cast-in-

place and precast

columns have the

similar hysteretic

behavior and energy

absorbed.

Skeleton curve

Comparing with PSC-

A-1and PSC-D-2，it is

indicated that the sleeve

has few effects on initial

stiffness . With loading

increases, the stiffness of

sleeve column (PSC-D-2)

decreases but ultimate

strength increases. There

is a longer platform at

ultimate strength to slow

down the stiffness

degrading.

PSC-A-1 vs PSC-D-2

Sleeve effects

Comparing with

PSC-E-3 and PSC-

C-4, it shows that the

specimen with shear

key has lower

strength but better

deformation and

slower stiffness

degrading than the

specimen with the

smooth joint.

PSC-E-3 vs PSC-C-4

Shear key effect

Skeleton curve

Comparing with

PSC-C-4 and PSC-B-6，it shows that the

specimen filled in high-

strength grouting

material in the joint

has higher strength but

less deformation than

the specimen filled in

concrete in the joint.

PSC-C-4 vs PSC-B-6

Grouting material effect

Skeleton curve

Ultimate Strength

No fc(MPa) Vu+(kN) Vu

-(kN) Vu+/fcbh0 Vu

-/fcbh0 Failure

PSC-A-1 34.39 472.7 -406.9 0.112 0.097 Shear

PSC-D-2 35.16 504.2 -396.1 0.117 0.092 Shear

PSC-E-3 38.06 520.6 -493.3 0.112 0.106 Shear

PSC-C-4 34.88 517.7 -438.8 0.121 0.103 Shear

PSC-B-6 38.82 520.3 -472.5 0.109 0.099 Shear

It is shown that the precast specimens have the similar

strength and failure modes as the cast-in-place

specimens.

Testing Conclusion

The rebar connected by the sleeve can insure the loading transfer, and the

sleeve has no bad effect on the columns;

The precast columns using three horizontal joint configurations have the

similar seismic behavior as the cast-in-place columns；

Since the limit specimens, the shear behavior and failure mode along the

joints can not be obtained. The test just proves that the precast column has

the behavior equal to cast-in-place column.

To investigate if the shear failure occurs along the joint for precast short

columns, numerical analysis is employed.

Finite Element Analysis of Precast Short Columns

Attaching the material property Concrete:

Damaged plastic model

Reinforcement:

Bi-linear model

• Finite element modeling

Modeling componentsas the dimension

Finite Element Modeling

划分网格，指定单元类型。

Defining interface and

assembling each component

Tie

Tie (Cast-in-place) or

Friction contact (Precast)

Embedded region

Specifying boundary condition

Encastre

Constraining Z

translation and three

rotations

Exerting loadings

Loading



Attaching the material property

Meshing and specifying element

Concrete:

three-dimensional

linear brick elements

Reinforcement:

truss elements


Finite Element Modeling

Defining interface and

assembling each component

Specifying boundary condition

Exerting loadings


Attaching the material property

Verifying the finite element model

Taking the PSC-A-1 as a example. When observing the equivalent plastic

tension strain（PEEQT），it shows the process of“bending cracks

occurring—diagonal cracks occurring—diagonal cracks developing—

damaging in shear mode”，and has a good agreement with the testing

observation。

1.3125mm 5.25mm 10.5mm 42mm

（1）Failure process and mode

The contact elements specified in the interface of joint indicates that

cracks occurred along the joints of specimens PSC-E-3、PSC-C-4、PSC-B-6, but didn’t go through the joints. It states that the damage was

not resulted by the shear sliding of the joints and agrees with the test

observation.

（2）Cracking in the joints of precast column

PSC-E-3 PSC-C-4 PSC-B-6


（3）Skeleton Curves


Since the sleeve and shear key are not

modeled In order to simplify the numerical

analysis, a few errors can be observed from

numerical results.

（4）Ultimate Strength

Specimen PSC-A-1 PSC-D-2 PSC-E-3 PSC-C-4 PSC-B-6

Testing（kN） 472.70 504.20 520.60 517.70 520.30

FE results（kN） 446.09 447.37 480.19 453.50 488.40

Relative Errors（%） 5.63 11.27 7.76 12.40 6.13

Testing（kN） -406.90 -396.10 -493.30 -438.80 -472.50

FE results（kN） -423.29 -428.69 -421.02 -411.06 -418.24

Relative errors（%） 4.03 8.23 14.65 6.32 11.48

Testing（kN） 439.80 450.15 506.95 478.25 496.40

FE results（kN） 434.67 438.03 450.60 432.28 453.32

Relative errors（%） 1.16 2.69 11.12 9.61 8.68

uV

-

uV

uV


The comparing between numerical analysis and testing results

indicates that the finite element models work well. It can be used to

stimulate the precast short columns

Parameter Analysis

To extend the test study, finite element parameter analysis is conducted.

For precast short columns the two important parameters to effect joint shear

behaviors are the axial compression ratio and shear-span ratio. By use of the

verified model, 9 numerical models are defined as the changes of axial

compression ratio and shear-span ratio.

Model shear-span

ratio

Column

height（mm）

axial

compression

ratio

Axial compression

（kN）

n0.6-1.5 1.5 1050 0.6 1290

n0.3-1.5 1.5 1050 0.3 645

n0.1-1.5 1.5 1050 0.1 215

n0.6-1.0 1.0 700 0.6 1290

n0.3-1.0 1.0 700 0.3 645

n0.1-1.0 1.0 700 0.1 215

n0.6-0.5 0.5 350 0.6 1290

n0.3-0.5 0.5 350 0.3 645

n0.1-0.5 0.5 350 0.1 215

Equivalent plastic strain

Comparing of columns

with fixed shear-span

ratio of 1.5 and

different axial

compression ratiosn0.6-1.5

n0.1-1.5

n0.3-1.5

With the decrease of axial

compression ratio, the

plastic strains increases

and implies that cracks

develop quickly and

damages occur early.

n0.6-1.5

n0.6-0.5

n0.6-1.0

With the decrease of

shear-span ratio, the

cracks occur from the

middle column and

develop diagonally in

a cross shape. But

the final failure modes

are similar and all in

the shear damage.

Equivalent plastic strain

Comparing of

columns with fixed

axial compression

ratio of 0.6 and

different shear-span

ratios

Joint states at failure stage

n0.6-1.5 n0.3-1.5 n0.1-1.5

n0.6-1.0 n0.3-1.0 n0.1-1.0

n0.6-0.5 n0.3-0.5 n0.1-0.5

• When the axial

compression ratio

changes from 0.6 to 0.3,

no sliding is observed

along the bottom joints. It

indicates that precast

columns fail as the cast-

in-place columns;

• When axial compression

ratio decreases to 0.1,

the obvious sliding

occurs along the joints.

The failure of precast

column is resulted by

Insufficient shear

strength of joints. The

failure belongs to

connection failure.

Rebar stresses at failure stage

n0.6-0.5 n0.3-0.5 n0.1-0.5

Stirrups yield but vertical rebar is in low stress

when columns damage. It indicates that the

column damage is the shear failure and dowel

action of rebar through joints doesn’t indicate.

Stirrups and rebar through the

joint yield. The column

damage comes from the shear

failure of the joint .

Hysterical Curves

When axial compression ration

decreasing to 0.1, the

deformation decreases and the

areas covered by hysterical

curve decrease. It implies that

the shear damage of joint is less

ductile than shear damage of

whole column.

With the decrease of shear-span

ratio, the stiffness increases but

plastic deformation decreases.

Under low axial compression

ratio and shear-span ratio（n0.1-

0.5），joint sliding occurs in the

first loading cycle.

Hysterical Curves

Skeleton curves

The ultimate strength decreases

with the axial compression ratio

deceasing. The ultimate

deformation under axial

compression ratio of 0.1 is more

less than that of 0.3 to 0.6

Under the same axial

compression ratio, the ultimate

strength increases and

deformation capacity

decreases with the shear-span

decreasing.

Skeleton curves

Ultimate strength

The ultimate strength deceases with the axial compression ratio

deceasing; and increases with the shear-span ratio deceasing.

Ultimate strength

Numerical analysis conclusion

The axial compression ratio is the key factor to effect the shear failure of

joints. It decides if the precast short column fails in the connection or in

the column self equal to the cast-in-place column.

For the precast short columns the shear failure will occur along the joints

when the axial compression ratio is low, i.e. 0.1. The failure is very brittle

with less deformation. Therefore when designing the precast short

columns with low axial compression ratio, it is necessary to check the

shear capacity for the joints.

The shear-span ratio affects the initial stiffness, deformation ability and

ultimate strength for precast short columns. With the decrease of shear-

span ratio, the initial stiffness and ultimate strength will enhanced, but

deformation will reduce.


• Japanese code

docuE VVV , max

2165.1 ycsddo ffAV

NVc

docuE VVV

• Chinese codeShear resistance from

friction along joint：

Shear resistance from rebar

dowel action force：

Friction coefficient：

Area of dowel rebar：

Tensile rebar is neglected。

Friction coefficient ：

0.8 for all

Area of dowel rebar：

All the rebar through the

joint is considered.

Calculating the shear strength of 9 models as the Chinese code and Japanese

code respectively （taking the same friction coefficient of 0.8）, the results are

shown in the table following：

No.

Axial

compressi

on ratio

Shear-

span ratioNumerical results(kN)

Calculations as

Japanese code(kN)

Calculations as

Chinese code(kN)

n0.1-1.5

0.1

1.5 277.03 228.46 537.54

n0.1-1.0 1.0 293.70 228.46 537.54

n0.1-0.5 0.5 345.26 228.46 537.54

n0.3-1.5

0.3

1.5 310.17 516.00 881.54

n0.3-1.0 1.0 333.49 516.00 881.54

n0.3-0.5 0.5 387.93 516.00 881.54

n0.6-1.5

0.6

1.5 339.02 1032.00 1397.54

n0.6-1.0 1.0 378.67 1032.00 1397.54

n0.6-0.5 0.5 425.26 1032.00 1397.54


When axial compression ratios are 0.3 and 0.6, the calculation results are higher than numerical

predictions for two codes. It indicates that the failure occurs in the columns. When axial

compression ratio is 0.1, Japanese code has a good agreement with numerical results.

Conclusion

The test of 5 specimens indicates that the precast columns with wet

connections have the similar strength, deformation and Energy

consumption ability as the cast-in-place columns.

Numerical analysis indicates that shear failure occurs along the joint

when axial compression is low. This damage is very brittle with less

deformation. To avoid the shear failure along the joint, the shear

strength of horizontal joints has to be checked when designing.

By comparing with Chinese code and Japanese code of precast

structures, the shear strength formula of Chinese code is

overestimate by considering both contact friction and rebar dowel

action together.

THANKS谢谢聆听

Nonlinear Finite Element Feng Xiong PhD Professor of Civil ...risedr.tongji.edu.cn/ubc/PPT/5.4/plenary 1/3 Feng XIONG-Nonlinear... · Feng Xiong PhD Professor of Civil ... Nonlinear

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