Authors: Davide Lavorato, Alessandro V. Bergami, Camillo Nuti, Bruno Briseghella, Junqing Xue, Angelo M. Tarantino, Giuseppe C. Marano, Silvia Santini

1. OpenSees Days Europe 2017
1st European Conference on OpenSees
Porto, Portugal, 19–20 June 2017
1
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
NUMERICAL INVESTIGATION ON THE
SEISMIC BEHAVIOR OF REPAIRED AND
RETROFITTED CHINESE BRIDGE PIERS
USING OPENSEES
Davide Lavorato1(*), Alessandro V. Bergami1, Camillo Nuti1,4, Bruno
Briseghella2, Junqing Xue2, Angelo M. Tarantino3, Giuseppe C. Marano2,
Silvia Santini1
1 Dept. of Architecture University of Roma Tre, Rome, Italy
2 College of Civil Engineering of Fuzhou University, Fuzhou, China
3 Dept. of Engineering, University of Modena and Reggio
4 Visiting Prof. of College of Civil Engineering of Fuzhou University,
Fuzhou, China
(*) davide.lavorato@uniroma3.it

2. C. Nuti University of Roma Tre (Roma, Italy)
B. Briseghella Fuzhou University (Fuzhou, China)
D. Lavorato University of Roma Tre (Roma, Italy)
A.V. Bergami University of Roma Tre (Roma, Italy)
G. Marano Fuzhou University (Fuzhou, China)
G. Monti University of Roma Uno (Roma, Italy)
A. M. Tarantino University of Modena (Modena, Italy)
Junqing Xue Fuzhou University (Fuzhou, China)
Silvia Santini University of Roma Tre (Roma, Italy)
THE RESEARCH GROUP FOR BRIDGE REPAIR AND
RETROFITTING:
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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3. 3
16th World Conference on Earthquake
16WCEE 2017, Santiago Chile, January
9th to 13th 2017
 Problem Definition
 Research Aims
 Case of Study
 Experimental tests
 Numerical analyses: monotonic vs cyclic tests
 Results and discussion
OUTLINE OF THE PRESENTATION:
Lavorato D. et al. paper davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
COMPDYN 2017
15-17 June 2017, Rhodes Island, Greece
6th International Conference on Computational
Methods in Structural Dynamics and
Earthquake Engineering
OpenSees Days Europe 2017
1st European Conference on OpenSees
Porto, Portugal, 19–20 June 2017

4. 4
 Existing RC bridge with damaged piers
after a seismic event
 Damage due to no proper transversal steel
reinforcement (modest shear strength and
ductility); no capacity design criteria
 A proposal for rapid repair and retrofitting
interventions
PROBLEM DEFINITION
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy

5.  After damaged concrete and steel rebar parts removal (Fig a)
 Each procedure (PR1, PR2) uses new shaped rebars (Fig b) connected to the original
undamaged ones by steel coupler and welding joints
TWO DIFFERENT REPAIR AND RETROFITTING
PROCEDURES (PR1 AND PR2):
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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 procedure PR1 uses self-compacting concrete (SCC) to build a concrete jacket (CJ) and
carbon Fiber Reinforced Polymer (CFRP) wrapping to assure the seismic improvements (Fig
c, d);
 procedure PR2 uses ultra-high performance fiber reinforced concrete (UHPFRC) with steel
fiber to build a CJ and to assure the seismic upgrading allowing time and cost saving (Fig c)

6. Remove damaged
parts
substitution
(long rebar
and stirrups)
Cast SCC
CFRP
Wrapping
REPAIR AND RETROFITTING SOLUTION PR1:
REPAIR AND
RETROFITTING
STEPS
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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7. REPAIR AND
RETROFITTING
STEPS
Remove damaged
parts
substitution (long
rebar ONLY)
Cast UHPC with
fiber
 time and cost saving because no stirrups and cfrp application
are necessary
REPAIR AND RETROFITTING SOLUTION PR2:
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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8. Vf
Fiber
content
VRd.UHFRC
fiber
concrete
jacket
[kN]
VRd,OC
original
pier
concrete
core
[kN]
VRd,tot
Total
[kN]
1 % 137.1
49.8
186.9
2 % 149.3 199.1
3 % 156.1 205.9
 Starting from experimental tests on materials
 Evaluating the Shear Strength contribution of the
new concrete part (VRd,UHFRC) by CNR-204/2006
 Using 2 % steel fiber ….
Vf
fcm6
[MPa]
fcm28
[MPa]
feq2
[MPa]
fFtuk
[MPa]
1 % 84 99 12.3 4.1
2 % 91 108 15.1 5.0
3 % 97 114 16.5 5.5
Table 2 – UHFRC mechanical properties:
percentage of fibers in concrete (Vf),
cylindrical compression strength after 6 days
(fcm6) and after 28 days (fcm28); equivalent
flexural strength (feq2), ultimate tensile
residual strength (fFtuk)
Crack Tip Opening
Displacement
Vrdtot (total strength) =VRd.UHFRC + VRd,OC
REPAIR AND RETROFITTING SOLUTION PR2:
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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We can guarantee the shear strength
necessary to sustain the seismic action by
capacity design (197kN)…

9. Scaled1:6
REPAIRED AND
RETROFITTED (PR1)
REPAIRED AND
RETROFITTED (PR2)
RETROFITTED ONLY
RETROFITTED ONLY
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EXPERIMENTAL RESEARCH CAMPAIGN PIER SPECIMENS RETROFITTED
ONLY (CONTROL SPECIMENS) OR REPAIRED AND RETROFITTED
THE RETROFITTED ONLY ARE OK IN CASE OF SEISMIC EXCITATION AND SO THEY ARE THE CONTROL SPECIMENS

10. retrofitted only or repaired and retrofitted by
the two procedures (PR1, PR2) at the Fuzhou
lab
266kN
The horizontal displacement history is the
one recorded during previous pseudo-
dynamic tests on bridge
So this history is representative of the one
of the pier in the bridge
EXPERIMENTAL CYCLIC TESTS ON PIER SPECIMENS
10
LAVORATO, D, NUTI, C, (2015). Pseudo-
dynamic tests on r.c. bridges repaired and
retrofitted after seismic damage. Engineering
Structures - Journal – Elsevier.

11. EXPERIMENTAL RESULTS OF THE CYCLIC TESTS ON
REPAIRED PIER SPECIMENS by PR1
VS RETROFITTED SPECIMEN ONLY
Lavorato D. et al. paper davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
REPAIRED AND
RETROFITTED (PR1)
 The maximum base shear of
the pier specimen repaired
by PR1 (R16-SCC-SR-1) is
smaller than the one of the
undamaged pier retrofitted
(P16-1) with the same CFRP
wrapping.
 This is due to the new
shaped rebar parts with a
reduced diameter and to …
what?
11

12. REPAIRED AND
RETROFITTED (PR2)
 The maximum base shear
of the pier specimen
repaired by PR2 (R16-
HSF-SR-0) is similar to the
one of the undamaged
retrofitted only (P16-2 )
 Also this specimen has
reduced rebars and so….
Why?
EXPERIMENTAL RESULTS OF THE CYCLIC TESTS ON
REPAIRED PIER SPECIMENS by PR2
VS RETROFITTED SPECIMEN ONLY
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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13. 13
NUMERICAL ANALYSES TO UNDERSTAND THE
EXPERIMENTAL BEHAVIOR OF THE TESTED
SPECIMENS… WORK IN PROGRESS FIRST RESULTS
Investigate the experimental results by FEM analyses
Using OPENSEES to build a generic fiber section with
different concrete parts and steel rebars
Evaluate section behavior by monotonic section analyses (to
understand the experimental maximum reaction)
Evaluate the cyclic behavior of the entire pier by cyclic
analysis on the pier specimen model (to understand the
seismic behavior of these specimens … WORK IN
PROGRESS
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy

14. 14
NUMERICAL FIBER SECTION ANALYSES by
OPENSEES:
The selected sections are:
 The section above the rebar connection for
the repaired and retrofitted specimens (rebar
reduction)
 The base section at pier anchorages for
retrofitted only specimens (no rebar
reduction; where the moment is greater)
The numerical axial load on each section was the experimental one
The section curvatures are increased monotonically
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy

15. Numerical analyses: section geometry
4 fiber models of 4 base sections
Ring for cover concrete or for the repaired concrete part
Central part for the confined core
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
Repaired
and retrofitted PR1
P16-1
P16-2
Retrofitted only
Repaired
and retrofitted PR2
retrofitted vs repaired and
retrofitted PR1: the only
difference is about the diameter
of the long. rebar (shaped for the
repaired specimen)
retrofitted vs repaired and
retrofitted PR2: different
diameter of the long rebar
(shaped for the repaired
specimen) and different concrete
UHFRFC for repaired zone
Retrofitted only

16. 16
Numerical analyses: material models
Concrete confined by CFRP and/or steel stirrups by Analytical
stress-strain model (Hosotani et al. )
UHPFRC by experimental curve
Steel fiber by test on rebar (shaped and not shaped)
Uniaxial Hysteretic material model OPENSEES to simply each
material behavior
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy

17. Numerical analyses: monotonic analyses results
The numerical analyses can reproduce well the maximum base
shear of the specimens measured during the experimental tests
(Fmax_exp)
 The results of these analyses are shown in Table in term of maximum moment on the
section (Mmax_num), maximum base shear (Fmax_num) of the specimen and height of
the section compression zone (zc_num).
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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Retrofitted only PR1 PR2

18. Numerical analyses: monotonic analyses results
Differences between the retrofitted only VS the repaired and
retrofitted by PR1 are essentially due to the shaped rebar
diameter reduction
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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Retrofitted only PR1

19. Numerical analyses: monotonic analyses results
The retrofitted only and the repaired and retrofitted by PR2 are
very similar even if the PR2 has shaped rebar
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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Retrofitted only PR2

20. Numerical analyses: monotonic analyses results
 The high value of the compressive strength of the UHPFRC reduces the
height zc_num of the section compression zone and increases the inner
lever arm of the section
 The increasing of the inner lever arms may contrast the decreasing of the
steel tensile resulting force due to the shaped rebar diameter reduction.
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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Retrofitted only PR2
Starting from the fiber
results we can obtain
the value of Zc_num
Zc_num

21. Numerical analyses: experimental VS numerical
results repaired and retrofitted PR1
 Cyclic test applying experimental
displacement history
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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22. Numerical analyses: numerical comparison
between PR1 and PR2
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
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 Cyclic test applying experimental
displacement history

23. OpenSees Days Europe 2017
1st European Conference on OpenSees
Porto, Portugal, 19–20 June 2017
23
Lavorato D. et al. davide.lavorato@uniroma3.it Dept. of Architecture University of Roma Tre, Rome, Italy
davide.lavorato@uniroma3.it
Thank you