seismic behavior of an existing concrete structure: assessment … · 2019-06-27 · ing. luca...
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Seismic behavior of an existing concrete structure: Assessment of
the reinforcement effect with a Pushover Analysis
24. CADFEM ANSYS SIMULATION CONFERENCE
Hochschule für Technik - RapperswilIng. Luca Bremen - Dr. Ing. Stefano Campana
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Table of content
19.06.2019 2CADFEM ANSYS Simulation Conference Rapperswil
• The speakers
• The Company
• Context of the problem
• Modeling in Ansys Mechanical
• Results
• Conclusions
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
The speakers
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• Luca Bremen, born in Lausanne in 1985, grown up in Ticino
• MSc EPFL in Civil Engineer in 2010– Master Thesis elaborated using ANSYS CFX
• Lombardi SA Ingegneri consulenti 2011-2013– Structural and Geotechincal Analysis
• Freelance Activity, 2015– Assessment of the Wind last acting on a tower building (ANSYS CFX)
• Passera & Associati SA, since 2016– Structural and Geotechnical Analysis (ANSYS Mechanical)
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
The speakers
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• Stefano Campana, born in Lugano in 1982, grown up in Ticino
• MSc EPFL in Civil Engineer in 2008
• PhD at the Structural Concrete Laboratory IBETON EPFL in 2012– PhD Thesis: «Éléments en béton armé sôumis à une combinaison de
flexion, effort tranchant et forces de déviation»
• Since 2013: Member Of Direction at Studio d’Ingegneria Passera & Associati SA and teacher of concrete structures atSUPSI
• Since 2017: Director of Studio d’Ingegneria Passera & Associati SA
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
The Company
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• Civil Engineering Office
• Domain fo activity– Structural Engineering
– Infrastructures
– Geotechnical Studies
– Environmental
– Hydraulic
• For additional information:– www.passing.ch
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Context of the problem
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• Current stantards impose that every construction undergoinga renovation must have its seismic safety verified. (SIA 269)– Seismic requirements were developed by the Swiss Norm SIA only
during the second half of 1900
– Lots of building are vulnerable because of the absence of a seismicconception
Existing structure - RS Analysis
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Context of the problem
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• Important notice: All values were changed due to Confidentiality Requirements by the client.
• Main characteristics of the building– Bearing structure composed by reinforced concrete frames
– Height: 18.50 m
– Width: 10 m
– Length: 18m
• Additional Masses of 60 t per floor
• Its characteristics suggest a Soft Storey Failure type
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Context of the problem
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Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Context of the problem
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• Seismic zone Z1 (SIA 261, Annex F)– Ground acceleration: 0.6 m/s2
– Foundation class: C
– Maximal acceleration on the Response Spectrum: 2.5 m/s2
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Context of the problem
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• The first seismic response was calculated through a ResponseSpectrum Analysis– Resistance of the weakest column only reached 24% of the acting
forces
– An important reinforcement was necessary in both directions, outersteel frames were proposed
– Along the transversal direction OK, along the longitudinal the impact on the façades is important
• The architect asked for a deepening of the seismic analysis in order to develop a better aesthetic solution
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Modeling
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• Beam 188 Elements
• Non-linear Moment-Curvature behavior of the columnsdefined through a bending test
• Model submitted to gravitational acceleration and an increasing horizontal acceleration
• Large deflection activated in order to identify instability failuremechanisms
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Modeling
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Existing structure Reinforced structure
Reinforcementb = 1 mOn the plane of the existing frame
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Modeling
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Existing cross section
500 mm x 850 mm
4x φ 30mm per side
Reinforcement cross section
1000 mm x 500 mm
6x φ 26mm per side
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Modeling
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• Assessment of the Moment Curvature relation– Through a 4 point bending test
– Beam was modeled using a layered section, reinforcement is smearedalong the section
– Non-linear Characteristics:
• Concrete: Drucker-Prager, Softening
• Steel: Bilinear Hardening
Existing structure Reinforcement
Steel class Type I (SIA 162 - 1956) B500B
Design Yielding stress 205 435
Concrete Class ~ C25/30 C30/37
Design uniaxial Compressive Strength 16 20
Design uniaxial Tensile Strength 2 2
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Results
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• Bending test
0
200'000
400'000
600'000
800'000
1'000'000
1'200'000
1'400'000
Mo
men
t [N
m]
Curvature [-]
Moment – Curvature (N = 0 kN)
Reinforced column RC - Hand calculated Existing column EC - Hand calculated
With concrete softening and steel hardening
No concrete softening and no steelhardening
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Results
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• Bending test – Concrete
– Reinforcement Steel
Minimum principal stress Maximum principal stress
Maximum principal stress
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Results
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• Structure
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Spec
tral
Acc
eler
atio
n [
m/s
2 ]
Displacement at the top [m]
ADRS Spectrums and Capacity Curves
SIA 261 ADRS Spectrum Local ADRS Spectrum Existing structure Reinforced structure
Soft storey collapse
Local instability collapse
Sufficient deformability and resistance of the structure
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Results
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• Existing structure– Soft storey collapse of the ground floor
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Results
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• Reinforced structure– Local instability of the lateral column
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Additional verifications
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• Shear forces
– Existing columns: VEd = 170 kN φ12mm@150mm
– Reinforcement: VEd = 780 kN φ14mm@100mm
• Local Stability of the bearing reinforcement bars
• Verification of the horizontal transfer of the seismic loads– Crossbeams
– Slabs
• Control of the foundation– Resistance and stiffness
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Conclusions
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• The current situation is better than the one showed by the response spectrum analysis
• Instability problems are difficult to assess throughconventional Response Spectrum Analysis– Caution with external reinforcement!
• A reinforcement of a single concrete column can provideenough resistance in order to fulfill the SIA 269/8 requirements
• The reinforcement has to be designed considering its plasticdeformation capacity in order to reduce the seismic loads
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Conclusions
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Reinforced structure - RS Analysis
Existing structure - RS Analysis
Reinforced structure - PushoverAnalysis
Existing structure - Pushover Analysis
Ing. Luca Bremen - Dr. Ing. Stefano Campana – Seismic behavior of an existing concrete structure: Assessment of the reinforcement effect with a Pushover Analysis
Thank you for yourattention!
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