Prefabricated High-Strength Rebar Systems with High ......•High-strength rebar (up to grade 120)...
Transcript of Prefabricated High-Strength Rebar Systems with High ......•High-strength rebar (up to grade 120)...
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Prefabricated High-Strength Rebar Systems with
High-Performance Concrete for Accelerated
Construction of Nuclear Concrete Structures
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Primary Objective
Reduce field construction times and fabrication costs of reinforced concrete nuclear structures through:
1) High-strength reinforcing steel bars (rebar)
2) Prefabricated rebar assemblies, including headed anchorages
3) High-strength concrete
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Collaboration
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Yahya C. Kurama, Ph.D., P.E. Ashley P. Thrall, Ph.D. Professor Myron and Rosemary Noble Assistant Professor
Scott Sanborn, Ph.D. Senior Technical Staff Member
Matthew Van Liew, P.E. Structural Engineer
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Notre Dame Research Team
Steve Barbachyn, Postdoc
Rob Devine, Graduate Student
Max Ducey, Undergraduate Student
Madalyn Sowar, Undergraduate Student
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Scope • Explore effectiveness, code conformity, and viability
of existing high-strength materials
• Focus on shear walls (ACI 349) – most common lateral load resisting members in nuclear structures (pressure vessels not in scope)
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• Aim to reduce complexities in rebar to improve construction quality and ease of inspection
US-APWR Design Control Doc.
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Scope:
High Strength Materials
• High-strength rebar (up to grade 120) with high-strength, high durability concrete (around 15 ksi)
• Concrete strength of 5 ksi typical in current practice
• ACI 349 limits headed bars and shear reinforcement to grade 60
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FHWA
5 0
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Strain, 0.001
Darwin et al. 2015
Stre
ss,
ksi
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Scope:
Prefabricated Rebar Assemblies
• Partially prefabricated cages for nuclear structural members (e.g., thick shear walls, slabs)
• Headed bars to reduce congestion (eliminates hooked bars)
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headed rebar (HRC-USA)
CRI Steel
hooked rebar
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Most Congested (current)
Least Congested (envisioned)
Potential Benefits
Multiple layers of hooked
Grade 60 bars
Fewer layers of hooked high-
strength bars
Fewer layers of headed high-
strength bars
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Project Tasks
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1- High-Strength Materials
Analytical study on limits/benefits, to:
• Establish effects of high-strength materials on structural deformation capacities
• Establish required concrete strengths so that use of high-strength rebar does not cause poor concrete performance
• Determine reduction in steel volumes
• Inform subsequent tasks of research on ACI 349 requirements that have greatest impact on design
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2- Prefab Rebar Cages • Evaluate prefab
headed rebar cages for:
- transportability
- liftability
- modularity
• Develop field procedures
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3- Optimization, Modeling, Design • Develop optimization procedure to select materials
and prefabrication solutions for:
- minimum fabrication cost
- minimum in-situ rebar cage assembly time
• Basic (design-level) and detailed (high-fidelity) numerical modeling
• Design of prototypes
• Pre-test design and analytical predictions
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4- Experimental Evaluation
• Testing of:
1) high-strength concrete and rebar materials
2) deep beams to establish basic characteristics of shear-controlled behavior
3) stub walls for pure shear strength of joints
4) wall panels for combined shear+flexure behavior
• Validation of analytical modeling and design
• Post-test analyses to extend results
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4.1- Material Testing • ASTM tests for concrete and rebar materials
- preliminary concrete mixes and rebar samples
- materials from laboratory specimen construction
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4.2- Deep Beam Tests • Varying V/M ratios within shear span to establish
basic characteristics of shear-controlled behavior
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V V V V
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4.3- Stub Wall Tests • Shear-wall-to-foundation joints under pure shear to
establish shear friction strength
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4.4- Wall Panel Tests • Representative wall panels under moment+shear
• Includes thermal loads to explore thermal cracking
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5- Recommendations
• Design, modeling, and construction recommendations on: - Appropriate high-strength materials
- Prefabricated headed rebar assemblies
- Basic (design-level) and detailed (high-fidelity) models
- Optimization for minimum cost/construction time
- Assumptions/approximations for design and analysis
- Effective field methods for concrete/rebar placement
• Design Procedure Document
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Roles of Collaborators
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• Modeling • Simulations
Recommendations
• Limit/cost-benefit Analyses • Analytical Modeling • Prototype Design • Experimental Testing • Design Procedure Document
• Design • Practice
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Questions?
http://phsrc-nuclearwalls.nd.edu