Development of a Seismic Design Methodology for Precast Floor Diaphragms

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Development of a Seismic Design Methodology for
Precast Floor Diaphragms An Overview

• Robert Fleischman, UA
• Clay Naito and Richard Sause, LU
• Jose Restrepo and Andre Filiatrault, UCSD
• S.K. Ghosh, S.K. Ghosh Associates, Inc.

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History

• PCI RD Committee distributed a Request for
  Proposal (RFP) in October 2002.

• Arizona-Lehigh-UCSD Consortium awarded grant from
  PCI for 200,000 in December 2002.

• PCI and University Consortium created
• Diaphragm Seismic Design Methodology (DSDM) Task
  Group
• Industry Advisory Panel
• Producer Member Partners (91,000 in specimen
  donations)

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History (cont)

• Proposal submitted to National Science Foundation
  (NSF) Grant Opportunities for Academic Liaison
  with Industry (GOALI) Program February 7, 2003.

• DSDM Consortium awarded GOALI grant from NSF for
  467,406 in August 2003.

• Initial DSDM Research Meeting held at PCI
  Headquarters, Chicago August 6, 2003.

• Official Start Date - October 2003 3 year
  duration

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DSDM Consortium
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Research Objective

• Develop a Seismic Design Methodology for Precast
  Concrete Diaphragms

• Design Force Patterns
• Internal Force Calculations
• Reinforcement Capacities
• Stiffness Calculations
• Flexibility Limits
• Structural Integrity Details

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Scope of Research

• To be jointly determined by DSDM Task Group and
  University Consortium, based on need and
  resources

• Topped and Pretopped Diaphragms
• Hollow Core and Double Tees Precast Units

• Low to High Seismic Zones
• Wall and Frame Structural Systems

• Existing and Promising Reinforcement Details
• Panel Joints, Beam Interfaces, Wall/Frame
  Anchorages, Topping/Precast Unit Bond

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Research Approach
Integrated Analysis and Experimentation
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DSDM Task Group

• Help to guide the physical scope
• Selection of prototype structures and candidate
  details
• Involvement with transformation of research
  results into an appropriate design methodology

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DSDM Task Group Activities

• Oversight
• Review and approve research program
• Regularly evaluate research direction

• Physical scope
• Select portfolio of prototype structures
• Select set of reinforcement details existing,
  promising
• Design of prototype structures

• Interface to design practice
• Evaluate existing code
• Gain consensus on approach to design methodology
• Transfer of research into practice and codes

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Industry Advisory Panel

• Organized to provide broad industry input to the
  project
• Includes precast producers, designers, and
  academics
• Facilitate aligning of research with existing and
  future efforts
• Participate semi-annually at Committee Days and
  PCI National Convention

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Producer Members

• Blakeslee Prestress, Inc.
• High Concrete Structures
• Precast/Prestressed Concrete Manufacturers
  Association of California
• Spancrete, Inc.
• Tindall-Virginia

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DSDM Research Project
Research Meeting 1
Three initial tasks were identified in RM1 as
keys to guiding the scope of the research

1. A general consensus on the form and intent of the
   design methodology
2. A portfolio of prototype structures
3. A set of reinforcing detail candidates

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Objectives
DSDM Research Meeting 1

1. Establish consensus on a design philosophy to
   guide research

• Role of Elastic Diaphragm Design and Need for
  Detailing for Ductility in High, Moderate, Low
  Seismic Zones
• Role of Web Reinforcement compliance vs.
  ductility
• Applicability of construction methods composite,
  non-composite, pretopped

• Applicability of Design/Analysis Methods Beam
  Analogy, Strut Tie Stringer-Panel
• Hollow Core details, emerging techniques and
  emphasis

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Diaphragm Design Methodology

• Template for Design Procedure

Overstrength Factors (W)

• For certain conditions, an overstrength factor is
  needed for elastic diaphragm response in the
  design earthquake
• Tradeoff exists between W and the ductility and
  drift demand in a severe seismic event

PROPOSED APPROACH Calibrate W through research.
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Diaphragm Design Methodology
Template for Design Procedure

• Classify diaphragms to give the designer
  flexibility to choose between a higher design
  force or special details.

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Diaphragm Design Methodology
Template for Design Procedure

• Prescribe different overstrength depending on
  zone, span and choice of reinforcing details

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Diaphragm Design Methodology
Template for Design Procedure

• Qualification standards/prequalify reinforcing
  details for use with the appropriate diaphragm
  classification

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Objectives
DSDM Research Meeting 1

1. Develop Portfolio of Prototype Structures to
   guide research on precast diaphragms

• Realistic designs for study
• Different classes of structures to explore
  diaphragm response
• A template for selecting test specimens
• A common benchmark to
• evaluate different details
• integrate research between the academic
  institutions
• evaluate economic and construction factors (IAP)
• Trial structures to formulate the design
  methodology

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Prototype Structure Portfolio
The Prototype Structure Portfolio should include
designs that are representative of

• Both typical but also challenging construction
• Double tee and Hollow core precast units
• Topped and Untopped floor systems
• Low and High Seismic Zone designs
• Construction practice across the country
• Wall and frame lateral systems of interior and
  exterior layout, and varying heights
• Various floor plans including squat, long and
  irregular

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Prototype Structure Candidates
Candidate 1 East coast parking structure

• 3-bay parking structure
• central ramp
• 300 x 181
• 12x60 DTs untopped
• pour strip over precast beams

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Prototype Structure Candidates
East coast parking structure (cont)

• Internal precast walls along the ramp

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Prototype Structure Candidates
Candidate 2 West Coast Office Building

• 3 story
• 163x136
• Interior shear walls Perimeter frames
• 4x27 HC
• Interior beams

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Prototype Structure Candidates
Candidate 3 West Coast Residential

• 5 story, 91 x 253 plan
• 4 x 15-25 HC
• Masonry Bearing wall

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Prototype Structure Candidates
Candidate 4 West Coast Parking Structure

• 9-story 2-bay
• 220 x 122 plan
• 10x60 DT
• Internal precast beam

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Prototype Structure Candidates
Candidate 5 West Coast Hotel

• 8 story structure 70'x220 in plan
• Shear walls in the short direction
• Moment frames in the long direction
• Post-tensioned flat plate investigate a precast
  alternative

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Prototype Precast Structures

• Candidates for Portfolio

Coverage of Parameters
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Objectives
DSDM Research Meeting 1

1. Establish candidate reinforcing details for use
   in analytical and experimental research

• Determine candidates based on existing research
  and industry feedback

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Feedback from Industry

• Double-Tee Panel-to-Panel Connections
• DC4 JVI Connector
• DC3 Topping with Connectors
• DC7 Bent Rebar Connector
• DC8-A Plate and Rebar Connector
• DC8-D1, DC8-B (Bent ) Stud Type with Inclined
  Plate
• DC9-A, 9-B,10, 11-A, 11-B Welded Cover Plate Type

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Feedback from Industry
Hollow-core Panel-to-Panel Connections

• HC1 Grouted shear key
• HC2 Slab edge serration below shear key
• HC3 Reinforced steel across longitudinal
  joints
• HC4 Embedded Steel plates with a welded steel
  plate cover across longitudinal joints

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Upcoming Research Activities

• UA Trial Analyses of Prototype Diaphragms
• Basic behavior
• Identify Critical Regions
• Approximate performance requirements
• LU Phase 1 Detail Tests
• Design and Fabricate Test Setup
• Commence Phase 1 Test
• UCSD Structural Level Examinations
• Design Shake Table Experiment
• Investigate Dynamic Performance of Prototype
  Structures

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We are grateful to PCI, producer members, and the
industry participants for their strong support of
this research. We look forward to a fruitful
research project culminating in a new seismic
design methodology for precast diaphragms.