seismic behavior of precast piers on high speed railway...
TRANSCRIPT
Seismic behavior of precast
piers on high speed railway
bridges
André Monteiro
António Arêde
Nelson Vila Pouca
2016
PhD 2016 | 2
2016 CONSTRUCT PhD Workshop
1. PhD framework:
• Main work developed on the scope of the SIPAV project.
• Challenged proposed by Mota-Engil, Betões e Prefabricados:
– Full-scale application viable for high-speed railway bridges (HSRL);
– Precast solution for fast construction;
– Reinforced concrete (RC) based layout;
– Focus on the piers for seismic behavior assessment;
HSRL Precast solution RC Piers Virtually non-existent
• State-of-art of relevant areas reviewed accordingly:
• Opportunity to address the shortcoming by aiming to apply
common precast solutions for HSRL Piers as well.
PhD 2016 | 3
2016 CONSTRUCT PhD Workshop
2. HSRL Bridge Piers:
• Common Layouts for HSRL Bridge piers:
Single Column Pier
(often with flare)
• Increased stiffness relative to equivalent motorway bridge piers.
• Strict deformation limits for HSRL running safety limit state, e.g.:
– Maximum radius for lateral deflection of 1.50 x 10-3 rad;
– Maximum longitudinal displacement of 5.00 mm;
• High seismic forces are expected.
Wall Pier
Multiple Column Pier
(Bent-type column)
Tall viaducts
Long/short viaducts
PhD 2016 | 4
2016 CONSTRUCT PhD Workshop
3. Base Structure for Study:
• Poceirão – Caia HSRL proposal for long and low height viaducts:
– Double Column RC Pier (5.00m < Hpier < 20.00m);
– Short span coupling beam (αs = 1.0);
– High stiffness columns;
Seismic design guidelines:
– Plastic hinges;
– High ductility;
• Height dependent stiffness ratios lead to difficulty in evaluating
suitable locations for inelastic
deformations.
• Possibility for high shear ductility
demand in the beams.
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Cu
rva
ture
(ra
d/m
)
H (m)
Elastic 50%Col_stiff 50%Beam_stiff MomCur_BEAM
PhD 2016 | 5
2016 CONSTRUCT PhD Workshop
4. Prototype Solutions:
• Beam reinforcement layouts based on applications for coupling
beams of shear walls:
Bi-diagonal layout (Eurocode 8 / ACI318 ).
Rhombic truss (Tegos and Penelis (1988)).
Dowel Rhombic truss (adapted from Tassios et al. (1996)).
• Precast system based on a top-down assembly (2 columns +
beam), enforcing reinforcement yielding at the joint.
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43
100% Asl
50% Asl
Moment
capacityStrain concentration Joint Opening
Monolithic Scenario Idealized Precast Scenario
VS.
Assembly Procedure
Precast Joint Reinforcement Design:
PhD 2016 | 6
2016 CONSTRUCT PhD Workshop
5. Experimental Campaign
• Test setup designed and installed in LESE accounting for:
– Constant axial loading on both columns (300 kN);
– Free rotation on column bases;
– Cyclic loading applied through shear;
Vertical Jacks Reaction Frame
Horizontal Actuator
Dywidag Ø26.5 Rods
Hinge System
Vertical Jacks
Threadbar Connection
Shear Loading Plates
Rotation Hinge
PhD 2016 | 7
2016 CONSTRUCT PhD Workshop
6. Main Observations
• Monolithic Specimens largely influenced by beam shear,
providing generally low ductility capacity.
Sliding shear
Diagonal splitting
Low ductility and energy dissipation
• Precast Specimens benefitting from the flexibility provided by the
joint, although still subjected to heavy damage.
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-4.00 -3.50 -3.00 -2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
Fo
rce (
kN
)
Lateral Drift (%)
Collapse
Yielding_cot1.8
Fu+ = 205.48 kN
Fu- = 171.44 kN
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-5.5 -4.5 -3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 4.5 5.5F
orce (
kN
)
Lateral Drift (%)
Collapse
Joint_bending
Beam_shear
Fu+ = 158.85 kN
Fu- = 147.99 kN
Large joint displacements
Heavy damage on larger drifts
Increased ductility
and energy dissipation
PhD 2016 | 8
2016 CONSTRUCT PhD Workshop
7. Numerical Modelling • 2D FEM based plane stress approach on Cast3m, with individual
constitutive characterization of:
– Concrete (Faria, R. and Oliver, J. (1993));
– Steel reinforcement (Menegotto, M. and Pinto, P. (1973));
– Bond-slip behavior (Eligehausen et al. (1982));
– Joint behavior (Snyman et al. (1991));
Monolithic specimen
Precast specimen
ε11 strains at first yielding:
σ22 stresses:
Monolithic specimen
Precast specimen
Rebar stresses:
Both specimens
PhD 2016 | 9
2016 CONSTRUCT PhD Workshop
8. Seismic Performance
• Experimental data used to calibrate global modelling tools for
seismic performance assessment:
– Viaduct modelling using 2D characterization in OpenSees;
– Lumped plasticity at the base of each pier calibrated accordingly, for Monolithic and
Precast specimens (Ibarra et al. (2005));
– IDA procedures (Vamvatsikos, D. and Cornell, C.A. (2002));
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CD
F (
DS
| I
M )
Instensity Measure, Sa1 (g)
Mono_yieldingPrecast_yieldingMono_ccrackingPrecast_ccrackingMono_collapsePrecast_collapse
DM #1 – Structural Damage
Comparison of different Damage Measures: DM #1 - Structural Damage;
DM #2 – Lateral Deflection;
DM #3 – Spectral Intensity;
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Drift (%)
Experimental_scaled
IMK_Pinched
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-5.50 -4.50 -3.50 -2.50 -1.50 -0.50 0.50 1.50 2.50 3.50 4.50 5.50
Drift (%)
Experimental_scaled
IMK_Pinched
Conclusions • A double column bent pier system was studied for
precast application;
• There is a high shear ductility demand in the beam of
the structural system, requiring unconventional
reinforcement layouts;
• Experimental evidence showed that the precast system
helps with increasing overall ductility and energy
dissipation;
• Numerical analyses confirm that the precast system is
able to globally improve the seismic performance of the
studied viaducts;
Thank you!