This is my M.S Degree PPT

1. Seismic behavior of renovated RC frame structure after
a column removal and retrofitted by post-tensioning
WAHAB ABDUL GHAFAR （阿加法）
M.S.in Structural Engineering
Student ID: M2015089
Advisor: Associate Prof. Fangfang Wei
College Of Civil And Transportation Engineering
28 October 2019

2. Introduction
Presentation outline
Experimental program
Numerical simulation and parametric
analysis
Conclusions
Aim and Objectives
Problem Statement
Methodology

3. Problem Statement
 With the development of society and improvement of the economy, many existing
buildings in densely populated cities cannot meet the structural function requirements
such as the need for more extensive space for the public..
 A feasible and economical approach to expanding the living area is removing
columns and masonry walls from existing framed structures and strengthening the
adjacent columns and the beams above removed columns or walls. So far, different
methods of column removal and strengthening have developed in engineering practice.
 There are a variety of different methods available to renovate and strengthen the
existing buildings, including fiber reinforced polymer composites, externally bonded
steel, external or internal post-tensioning methods, and section enlargement.

4. Retrofitted RC frame
28 October 2019
Introduction
Isotropic view Elevation View
1. First, a middle column was removed from the original existing RC frame structure.
2. Retrofitted and strengthened the beams above the removed column by post-tensioning.
3. Retrofitted and strengthened the two adjacent columns by casting a new layer of reinforced concrete.

5. 28 October 2019
Aim and Objectives
Aim
 The aim of this study is to investigate the seismic behavior of a renovated RC frame structure after a column is
removed from the existing RC frame structure and the beam above the removed column strengthened by post-
tensioning method and retrofitted the two adjacent columns by concrete jacketing.
objectives
 To show experimentally the seismic behavior of existing RC frame and renovated frames;
 To investigate numerically the seismic behavior of existing RC frame and renovated frames;
 Validate the numerical models through comparison of hysteresis curve and envelope curve with available
experimental data.
 To conduct a parametric study to investigate the retrofitted beam column sensitive and insensitive parameter
impacts.

6. 28 October 2019
Methodology
Experimental
program
Design of
prototype
frame
Numerical
simulation using
Open-Sees
Parametric
analysis

7. 28 October 2019
Experimental program
 A total of two specimens RC Frame Structures are designed and built according to the seismic design
code of China (GB500011) [29].
 The first specimen is constructed to represent the original existing RC frame (OF) and the second one
is built to serve the renovated RC frame (PF).

8. 28 October 2019
Experimental program
Fig 3-1 The Original Frame Dimensions and reinforcement details
Fig 3-2 The OF Cross section Dimensions and reinforcement details
 A two-story-two-bay RC framed structure was taken from a six-story existing structure then analysed and designed by
using SAP2000 and fabricated at scale 1/3

9. 28 October 2019
2. Renovated RC Frame by Post-Tensioning (PF)
Experimental program
For post-tensioning beam, Post-tensioned tendon which had 1x7 wire twisted steel strand is used.
The ultimate strength is 1860(N/mm2) ,and the yield stress is 1580(N/mm2) .
Fig 3-3 Pre-Stressed Frame Dimensions and reinforcement details
Fig 3-4 The PF Cross section Dimensions and reinforcement details.
15.2

10. 28 October 2019
Table 3-1 Material properties
Experimental program
Steel bar
Diameter
(mm）
Yield strength
(MPa）
Ultimate strength
(MPa）
 6 490.1 677.02
 10 478.5 652.73
 14 467.9 629.42
 20 453.2 638.83
Concrete C30 Compressive strength fcu （MPa） 31.1
ConcreteC40 compressive strength fcu （MPa） 41.1

11. 28 October 2019
Experimental program
Actuator
Loading cell
beam
Horizontal rods
Ground beamStrong floor
Anchor
bolts
Loading
beam
Prestressed
rods
Test Setup and Loading
The cyclic test set-up for the frame specimens shown in Figure 3-7. The frame consisted of a horizontal loading system, two
vertical loading systems, and boundary restraints.
Fig 3-9 Cyclic loading pattern
Fig 3-7 Cyclic loading test set-up for frame specimens

12. 28 October 2019
Experimental Results
1. The OF Specimen
Fig 3-23 Skeleton curveFig 3-21 OF hysteresis curve
-120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
Force(kN)
Displacement (mm)
-120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
Force(kN)
Displacement (mm)
Fig 3-10 Column -beam joint cracks concrete crushed
0 10 20 30 40 50 60 70 80 90 100 110
0
2
4
6
8
10
12
Stiffness(kN/mm)
Diceplacement (mm) 0 10 20 30 40 50 60 70 80 90 100 110 120
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Energydissipation(kN.mm)
Displacement (mm)
Fig 3-17 Energy dissipation capacity
Fig 3-16 Stiffness degradation curves

13. 28 October 2019
2. The PF specimen
Experimental Results
Fig 3-22 PF hysteresis curve Fig 3-24 Skeleton curve
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
Force(kN)
Displacement (mm)
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
Force(kN)
Diceplacement (mm)
Fig 3-13 Right column second floor concrete crushed rebar buckling
Fig 3-12 Cracks in the middle column and Post-tensioning beam
0 10 20 30 40 50 60 70 80
0
2
4
6
8
10
12
14
16
18
20
22
24
Stiffness(kN/mm)
Diceplacement (mm) 0 10 20 30 40 50 60 70 80
0
1000
2000
3000
4000
5000
6000
7000
8000
Energydissipation(kN.mm)
Displacement (mm)
Fig 3-17 Energy dissipation capacityFig 3-16 Stiffness degradation curves

14. 28 October 2019
ID Yield displacement y /（mm） Ultimate displacement u /
（mm）
Ductility
ratio
Level of
ductility
OF 19.29 102.11 5.29 High
PF 10.45 62.16 5.94 High
Experimental Results
The OF and PF Ductility Capacity
Table 3-2 Essential parameters from the observed cyclic loading
yuu  /

15. 28 October 2019
Numerical simulation
Introduction
The finite-element (FE) method widely recognized as a powerful tool is used to model and simulate a response to static
and dynamic loads of structures. In recent years, commercial and uncommercial FEM software packages have been
developed which provides reliable tools to model and analyze structures under linear and nonlinear response of loads.
Overview of Open-Sees
Open System for Earthquake Engineering Simulation (Open-Sees) is a structural analysis software. This program was
developed by Pacific Earthquake Engineering Research Center (PEER) McKenna and Fenves (2002).
Fig 4-1 Principal objects in Open-Sees

16. 28 October 2019
RC Frame Modeling in Open-Sees
The nonlinear behavior of the RC beam and columns was modeled by utilizing the fiber model elements. The columns
and beams are represented by the Force Base Beam-Column(FBBC) elements. The cross sections are defined using fiber
discretization with distinct fibers for steel reinforcement. Each element has five integration points. Concrete material that
includes unconfined (cover) and confined (core) concrete is modeled using the Concrete02 material model and steel material
used Steel02 .
Numerical simulation
Fig 4-3 OF modeling scheme in Open-Sees

17. 28 October 2019
Post-tensioning beam Modeling in OpenSees
Numerical simulation
Fig 4-11 PF modeling scheme in Open-Sees
SFC 5, 6, 7 FBBCE
FCS 8, 9 FBBCE
Elements 1, 2 FBBCE SFC
PSFC 3, 4 FBBCE Post-stressing tendons simulated by truss element 3, 4 FBBCE
Post- stressing tendon
Steel Rebar Confined Concrete
Unconfined Concrete
Post-stressing tendon
OpenSees Concrete02 uniaxial material model Steel02 Material -- Giuffré-Menegotto-Pinto Model
Fig 4-8 Stress-strain relationship for confined and unconfined
concrete kent and park
Fig 4-10 Constitutive relationship of pre-stressing tendons

18. 28 October 2019
Numerical Results and validation
-120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
Experimental
Numerical
Force(kN)
Displacement (mm)
Fig 4-12 Hysteresis comparison of analytical and experimental results of OF
1. The OF Specimen
0 10 20 30 40 50 60 70 80 90 100 110 120
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Experimental
Numerical
Energydissipation(kN.mm)
Displacement (mm)
Fig 4-18 Energy dissipation capacity
0 10 20 30 40 50 60 70 80 90 100 110
0
2
4
6
8
10
12
Stiffness(kN/mm)
Diceplacement (mm)
Experimental
Numerical
Fig 4-17 Stiffness degradation
0 10 20 30 40 50 60 70 80 90 100 110 120
0
10
20
30
40
50
60
70
80
90
100
110
120
Force(kN)
Displacement (mm)
Experimental
Numerical
Fig 4-16 Envelope curves comparison of numerical and experimental

19. 28 October 2019
Numerical Results and validation
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
Experimental
Numerical
Force(KN)
Displacement (mm)
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
Experimental
Numerical
Force(KN)
Displacement (mm)
0 10 20 30 40 50 60 70 80
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Experimental
Numerical (Truss)
Numerical (PSFC)
Force(kN)
Displacement (mm)
Fig 4-14 Hysteresis comparison of analytical and experimental results of PF PSFC and truss
2. The PF specimen
0 10 20 30 40 50 60 70 80
0
2
4
6
8
10
12
14
16
18
20
22
24
Stiffness(kN/mm)
Diceplacement (mm)
Experimental
Numerical
0 10 20 30 40 50 60 70 80
0
1000
2000
3000
4000
5000
6000
7000
8000
Experimental
Numerical
Energydissipation(kN.mm)
Displacement (mm)
Fig 4-16 Envelope curves comparison of numerical and experimental
Fig 4-18 Energy dissipation capacityFig 4-17 Stiffness degradation
PSFC
PF with Truss Element

20. 28 October 2019
Parametric analysis
Specimen
designation
Columns axial load
ratio (%)
Retrofitted
beam
reinforcement
ratio (%)
Retrofitted
columns
reinforcement
ratio (%)
Retrofitted
beam
post-
tensioning
tendons
ratio (%)
Retrofitted
beam cross-
section
Retrofitted
columns
cross-section
depth
(mm)
width
(mm)
depth
(mm)
width
(mm)left middle right
NPF 0.097 0.16 0.097 1.16 1.3 0.23 400 300 350 350
NPF1 0.16 0.252 0.16 1.16 1.3 0.23 400 300 350 350
NPF2 0.097 0.16 0.097 1.96 1.3 0.23 400 300 350 350
NPF3 0.097 0.16 0.097 1.16 2.3 0.23 400 300 350 350
NPF4 0.097 0.16 0.097 1.16 1.3 0.46 400 300 350 350
NPF5 0.097 0.16 0.097 1.16 1.3 0.23 450 350 350 350
NPF6 0.097 0.16 0.097 1.16 1.3 0.23 300 250 350 350
NPF7 0.097 0.16 0.097 1.16 1.3 0.23 400 300
400
400
NPF8 0.097 0.16 0.097 1.16 1.3 0.23 400 300 300 300
Table 4-1 Important parameters for parametric analysis

21. 28 October 2019
Parametric analysis
The retrofitted method applied
between…
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
160
NPF
NPF1
Force(kN)
Displacement (mm)
0 5 10 15 20 25 30 35 40
0
50
100
150
200
250
300
350
400
450
500
550
600
Totalappliedload(kN)
Mid-span deflection (mm)
NPF
NPF1
1. Axial load ratio impact
Fig 4-20 Proposed retrofitting RC frame on the different floor (unit: mm).
Fig 4-21 Hysteresis curves

22. 28 October 2019
Parametric analysis
2. Retrofitted beam reinforcement ratio impact
3. Retrofitted columns reinforcement ratio impact
4. Retrofitted post-tensioning beam tendons ratio impact
0 10 20 30 40 50 60 70 80
0
20
40
60
80
100
120
140
160
Force(kN)
Displacement (mm)
NPF
NPF2
NPF3
NPF4
0 2 4 6 8 10 12 14 16 18 20
0
50
100
150
200
250
300
350
400
Totalappliedload(kN)
Mid-span deflection (mm)
NPF
NPF2
NPF3
NPF4
Fig 4-25 Envelope curves Fig 4-33 Mid-span deflection of Post-tensioned beam

23. 28 October 2019
Parametric analysis
5. Retrofitted beam cross-section impacts
6. Retrofitted columns cross-section impacts
Fig 4-32 Envelope curves Fig 4-33 Mid-span deflection of Post-tensioned beam
0 10 20 30 40 50 60 70 80
0
20
40
60
80
100
120
140
160
Force(kN)
Displacement (mm)
NPF
NPF5
NPF6
NPF7
NPF8
0 5 10 15 20 25 30
0
50
100
150
200
250
300
350
400
Totalappliedload(kN)
Mid-span deflection (mm)
NPF
NPF5
NPF6
NPF7
NPF8

24. 28 October 2019
Conclusion
1. In this study, a post-tensioning method and concrete jacketing was developed to retrofit and upgrade the
RC framed structure after a column removal.
2. The seismic behavior of two specimen was investigated under the cyclic loading
3. All these specimens were numerically investigated in Finite Element program Open Sees (Open System
for Earthquake Engineering Simulation) and the obtained result compared and validated with available
experimental results.
4. Parametric analysis was conducted to find out the impact of sensitive and insensitive parameters, and
the following parameter effects were determined which had more impacts on the entire structural
behavior.
5. Axial load ratio and the retrofitted beam and columns cross-section was the sensitive parameter with
significant impact. The retrofitted beam column steel rebar and tendon ratio was rarely sensitive
parameters in this study .

25. 28 October 2019
Thank you
谢谢