Seismic behavior of precast piers on high speed railway...
Transcript of Seismic behavior of precast piers on high speed railway...
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.
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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
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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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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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100% Asl
50% Asl
Moment
capacityStrain concentration Joint Opening
Monolithic Scenario Idealized Precast Scenario
VS.
Assembly Procedure
Precast Joint Reinforcement Design:
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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
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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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Fo
rce (
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Lateral Drift (%)
Collapse
Yielding_cot1.8
Fu+ = 205.48 kN
Fu- = 171.44 kN
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orce (
kN
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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
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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
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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
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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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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!