New Paradigm in Earthquaker Engineering of Bridges-Resilient, Fast, Recyclable
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Autor: Mehdi Saiid Saiidi Fecha: 2017/11
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New Paradigm in Earthquaker Engineering of Bridges-Resilient, Fast, Recyclable
- 1. 1 New Paradigm in Earthquake Engineering of Bridges- Resilient, Fast, Recyclable M. Saiid Saiidi http://wolfweb.unr.edu/homepage/saiidi/ Professor, Department of Civil and Environmental Engineering Director, Center for Advanced Technology in Bridges and Infrastructure Co-Director, ABC-UTC Research Assistants Zachary Haber, PhD, Project Engineer Genex Systems, Washington, DC Mostafa Tazarv, PhD, Asst. Prof. S. Dakota State Univ., Brookings Melissa O’Brien, MSCE, Structural Engineer Sebastian Varela, PhD, Freese & Nickols, Forth Worth, Texas Fatemeh Kavianipour, PhD, Staff Engineer, Kleinfelder, San Diego, California Brian Nakashoji, MSCE, Structural Engineer, Professional Service Industries, Washington, DC
- 2. 2 UNR EQ Engineering Lab— Largest facility in the US w/ 4 shake tables
- 3. 3 Modern Concepts in Bridges 1- Novel materials 2- Novel construction approach Novel Materials in Earthquake- Resistant Concrete Bridges • Performance during earthquake • Serviceability after earthquake New
- 4. 4 Target performance for standard bridges during earthquake: No Collapse Damaged Bridges Have to Be Closed -Ambulances and fire trucks -Other emergency response vehicles -Public transportation -Major economic impact (locally; can be regional and global)
- 5. 5 • Serviceability after earthquake: Minimize permanent drift and damage • Advanced materials/details Shape memory alloys Ductile concrete/UHPC Columns w/ built-in elastomeric pads Fiber-reinforced polymers Post-tensioning Concrete + Steel >> One Combination Advanced Materials/Details >> Over 40 Combinations Only 8 have been proof tested!
- 6. 6 Novel Columns – NCHRP 12-101 Footing FRP Jacket Reinforcing Steel Concrete Footing FRP Jacket Reinforcing Steel Concrete FRPTendon Footing FRP Jacket Reinforcing Steel Concrete SteelTendon Footing FRP Jacket Reinforcing Steel Concrete FRP Rubber Tendon Footing FRP Jacket Reinforcing Steel Concrete Steel Rubber Tendon Footing Reinforcing Steel Concrete FRP Rubber Tendon Footing Reinforcing Steel Concrete Steel Rubber Tendon Footing FRP Jacket Reinforcing SMA Concrete Coupler Footing FRP Jacket Reinforcing FRP Concrete Footing FRP Jacket Reinforcing SMA Concrete Rubber Coupler Footing FRP Jacket Reinforcing SMA Rubber Coupler FRP Tendon Concrete Footing FRP Jacket Reinforcing FRP Rubber FRP Tendon Concrete Footing FRP Jacket Reinforcing SMA Rubber Coupler Steel Tendon Concrete Footing Reinforcing Steel UHPC Footing Reinforcing Steel UHPC FRP Jacket Footing Reinforcing Steel UHPC FRPTendon Column Type 1 to 16 Evolution in SMA (Nickel Titanium) Use/Research Also military applications
- 7. 7 Shape Memory Alloy • Superelastic response • Shape memory effects • NiTi SMA developed in1962 • Cu-Al-Mn SMA being developed • Fe-based SMAs– not superelastic NiTi Bar Application • Very expensive! Approx. 90 x steel cost • Limit its use only in plastic hinges Steel NiTi Steel
- 8. 8 Combining SMA Bars with Engineered Cementitious Composites (ECC, Ductile Concrete) 1. Fiber-reinforced cementitious composite 2. Tensile strain-hardening behavior 3. Typically 2% or less fiber content by volume Combining SMA Bars with Engineered Cementitious Composites (ECC, Ductile Concrete) Polyvinyl Alcohol Fiber 0 200 400 600 800 1000 0 0.5 1 1.5 2 2.5 3 3.5 4 Strain(%) TensileStress(psi) 0 1.4 2.8 4.2 5.6 7 TensileStress(MPa) Conventional Concrete ECC
- 9. 9 SR99-RC (8% Drift) SR99-LSE (12% Drift) SR99-SSE (10% Drift) Damage at End of Testing SR99-RC Force-Displacement Hysteresis
- 10. 10 0 1 2 3 4 5 6 7 0 2 4 6 8 10 12 ResidualDrift(%) Drift (%) Measured Residual Drift Ratios SR99-RC SR99-LSE SR99-SSE Novel Construction Concept-Precast Bridges>> Accelerated Bridge Construction (ABC) • Motivation: Minimize traffic interruption • Main advantages: – Better quality bridges because of casting in plants – Reduced construction zone accidents • Main disadvantages: – Requires more precision – Connections in high seismic areas- limited test data (emerging)
- 11. 11 Why high seismic zone matters? • ABC relies on precast members that are connected in the field. Connecting Columns to Cap Beams/Footings Coupler Option Grouted sleeves Headed bar couplers Swaged Shear screw Non-Coupler Option Grouted ducts Prestressed systems Pocket connections Embedded columns Others Pins/hinges Replaceable connections Etc.
- 12. 12 Coupler (Mechanical Bar Splice) Connections Code Coupler Type Plastic Hinge AASHTO Full Mech. Connection No Caltrans Service No Ultimate No ACI Type 1 No Type 2 Yes Recent Seismic Studies of Columns w/ Couplers Grouted Couplers in Nevada, Utah, Florida Displacement ductility of 4.5 or more Headed Bar Couplers in Nevada Displacement ductility of 7- same as CIP QUESTION: Should the ban on couplers in plastic hinges be removed?
- 13. 13 Grouted ducts Prestressed Systems Non-Coupler Option Grouted ducts Prestressed systems Pocket connections Embedded columns 4 New Details Post-tensioned segmental columns wrapped with CFRP Concrete filled tube CIP columns Concrete filled tube precast columns Pipe pin
- 15. 15
- 16. 16 After Final Run (9% drift) CIP Bent Precast Bent
- 17. 17 Current ABC System Studies at UNR PI: Saiidi • Three 0.35-scale, 2-span bridge models • Two with concrete superstructure; one with steel superstructure • One concrete and the steel bridge under construction- Testing: Sept. 2017 and Jan. 2018 34 Caltrans Bridge 1 Study the performance under bidirectional earthquakes of two large-scale bridge systems incorporating ABC connections
- 18. 18 35 Bridge 1 • Deck: ts=8” ’ 5 ksi • Girders: CAWF-48 34 0.6”-dia. strands ’ 8 ksi • Columns: =4.5’ 18#14 ( 1.77%) #8@4” ( 1.61%) ’ 4 ksi • Caltrans SDC and BDS Caltrans Amendments to AASHTO LRFD AASHTO-LRFD 36 Abutment End Diaphragm Intermediate Diaphragms Deck Pockets Extended bars to splice over the pier Shear Connectors
- 19. 19 Test Day: Sept 20, 2017
- 20. 20 Deconstructible bridges w/ advanced materials Combines novel materials and ABC Objectives: Develop bridge columns that 1- Withstand strong earthquakes with no or minor damage so they are useable after earthquakes. 2- Can be disassembled and reused. 6% of CO2 emission in the world is from cement factories.
- 21. 21 Plastic Hinge Elements Longitudinal Reinforcement in PH Shape Memory Alloys (SMA) Ni-Ti Cu-Al-MN
- 22. 22 Capacity-protected column outside PH ECC; NiTi; Copper Based SMA; Rubber; CFRP Shell Rubber Pad
- 23. 23 Apparent damage in CE-R Two-Span Bridge Model
- 24. 24 Original Bridge- Test to 6% Drift After disassembly
- 25. 25 Reassembled Bridge Test to Failure (10% drift) Implementation of SMA/ECC in Showcase Bridge • Alaska Way Viaduct Replacement, Seattle, WA • Three Spans (110ft; 180ft, 110ft) • Precast Post-Tensioned Splice Tub Girder • Single Column Piers • Square Columns (5ft x 5ft) w/ Circular Core • ECC Full Length of Column
- 26. 26 Nickel-Titanium Bars • Challenges with including SMA in a contract – Cost • ASTM A706 = $1 / lb. • SMA = $87 / lb. – Schedule – 6 month delivery, not including process to head bar for mechanical splice – Mechanical splice required in hinge region HRC Couplers in Seattle Alaska Way Viaduct- CIP
- 27. 27
- 28. 28 Message • Embracing novel materials and construction concepts could transform the bridge engineering field to more resilient and durable bridges that better serve the public.