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Innovative Seismic Design Methodology for Precast Diaphragms Research

This research project focuses on developing a seismic design methodology for precast concrete diaphragms through an integrated analytical and experimental approach. The project involves a consortium of organizations working towards improving seismic design practices. Through analytical studies and experimental testing, the goal is to enhance the understanding and implementation of seismic-resistant structures.

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Innovative Seismic Design Methodology for Precast Diaphragms Research

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  1. Integrated Analytical and Experimental Approach toPrecast Concrete Diaphragm Research José I. Restrepo, UCSD Robert Fleischman, UA Clay Naito and Richard Sause, LU S.K. Ghosh, S.K. Ghosh Associates, Inc.

  2. Background • Arizona-Lehigh-UCSD Consortium awarded grant from PCI for $200,000 in December 2002. • Diaphragm Seismic Design Methodology (DSDM) Task Group Established • Producer Member Donations Identified ($91,000) • Arizona-Lehigh-UCSD Consortium awarded GOALI grant from NSF for $467,406 in August 2003 • Official Start Date - October 2003 – 3 year duration

  3. DSDM Consortium PCI, IAP DSDM Task Group

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

  5. Research Objective Develop a Seismic Design Methodology for Precast Diaphragms

  6. DSDM Task Group • Help to guide the physical scope • Selection of prototype structures in terms of lateral system types, story height, and floor plan • Involvement with transformation of research results into an appropriate design methodology S.K.Ghosh DSDM Task Group Chair President, S. K. Ghosh Associates R. Becker Vice President Spancrete Industries, Inc. N. Cleland President Blue Ridge Design, Inc. Tom D’Arcy President Consulting Engineers Group N. Hawkins Professor Emeritus Univ. of Illinois Paul Johal Research Director PCI Joe Maffei Engineering Consultant Rutherford & Chekene Engineers Susie Nakaki President The Nakaki Bashaw Group, Inc.

  7. Diaphragm Classification (DC) Designation Seismic Zones Ordinary OD A,B,C Intermediate ID B,C,D,E Special SD D,E,F DSDM Task Group Activities • Review and approve research program • Evaluate existing code • Gain consensus on design approach • Determine physical scope: • initial set of reinforcement details: existing, promising • prototype structures: systems and seismic zones • representative floor plans: layout, construction • Design of prototype structures • Periodically evaluate research direction • Transfer of research into practice and codes

  8. Research Scope 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 • Prototypes: Structural System, Seismic Zone • Representative Floor Plans • Existing and Promising Reinforcement Details • Panel Joints, Beam Interfaces, Wall/Frame Anchorages, Topping/Precast Unit Bond

  9. Design Objectives of Methodology Seismic Design Methodology for Precast Concrete Diaphragms must include: • Diaphragm Design Force Patterns • Diaphragm Internal Force Calculations • Diaphragm Stiffness Calculations • Diaphragm Reinforcement Capacities • Diaphragm Flexibility Limits • Diaphragm Structural Integrity Details

  10. Research Required to meet Design Objectives • force demands on the overall diaphragm • internal force distribution for calculating reinforcement • force combinations at sections • axial-flexure interaction in collectors • deformation patterns and local ductility demands • diaphragm-induced drift demands Research to determine the likely:

  11. Research Challenge Challenges exist in determining these values: • Inertial force demands depend on overall structural dynamics including diaphragm flexibility effects – extreme instantaneous load events are likely (Design Force Pattern) • Load paths are dependent on details and floor plan layout (Internal Force Calculation). • Gravity system drifts are related to floor span, lateral system type and diaphragm design strength (Flexibility Limits). • Given extreme load events, ductility demands are difficult to avoid in severe earthquake (Structural Integrity Details) These issues are the result of interrelated behaviors that encompass response at the detail, joint, diaphragm and structural level. Uncoupling these responses or relying on idealized (analytical) boundary conditions to extrapolate response will likely produce incorrect conclusions.

  12. UA Analyses link UCSD structure tests with LU detail tests. Research Approach: Integrated Analysis and Experimentation

  13. Research Program at UCSD • University of California, San Diego Investigators • Sponsors • PCI • PCMAC • Spancrete J. Restrepo, Ph.D. PCI Committee Days April 2003

  14. Scope of Project at UC San Diego • Analytical work for determining floor acceleration demands for the design of buildings with rigid diaphragms • Shake table experimental work to assess the System’s response

  15. Experimental Program at UC San Diego • Three-story one-quarter scale building with a 3:1 aspect diaphragm

  16. Experimental Program at UC San Diego • Each level will incorporate a representative type of precast concrete diaphragm and typical connection details used in practice • Two floors with topped diaphragms • One floor with an untopped diaphragm • Diaphragm reinforcement design TBD: • Current code • New methodology

  17. Experimental Program at UC San Diego • Building response characterization: • Initial simple and refined non-linear time-history analyses to be conducted by UCSD and UA • Testing Phase: • Quasi-static testing: to determine the diaphragm flexibility at each level • Dynamic testing: to determine the system’s dynamic response

  18. Experimental Program at UC San Diego Building Elevation and Quasi-static Testing of Diaphragm

  19. Experimental Program at UC San Diego • Shake-table dynamic testing: • To follow the test protocol successfully used for the testing of the Caltech-Curee Woodframe house • Ensemble of time-histories: • Pulse-loading • Band-limited white noise • Historic ground motions, including a near-fault record

  20. Analytical Program at the University of Arizona • Analysis will link structure/diaphragm level experiments at UCSD with joint/reinforcing detail level experiments at Lehigh. Robert B. Fleischman, Ph.D. University of Arizona

  21. Analytical Program at the University of Arizona Two-stage approach adopted in previous research will be extended: • Nonlinear static (pushover) analyses of individual diaphragms • diaphragm models will be based on data from Lehigh baseline tests and existing data • Nonlinear dynamic analysis of structures under earthquake • models of prototype structures will be based on diaphragm analyses and UCSD quasi-static tests • Together, the two stages, suggest the Lehigh MCD tests: • structure analyses provide demand levels • diaphragm analyses provide boundary conditions and critical regions • analyses verified or calibrated by shake table tests

  22. Research Program at Lehigh University • Lehigh University Investigators • Sponsors • PCI • ATLSS/PITA • High Concrete Industries • Blakeslee Prestress Inc. • Tindall-Virginia C. Naito, Ph.D., P.E. R. Sause, Ph.D., P.E. Engineering Research Center PCI Committee Days April 2003

  23. Research Program at Lehigh University • Experimental Investigation of Precast Units/Joint Reinforcement Details • Detailed Finite Element Investigation of Joint Connection Performance • Simplified Analytical Models Engineering Research Center PCI Committee Days April 2003

  24. Experimental Investigation of Precast Units/Joint Reinforcement Details Engineering Research Center PCI Committee Days April 2003

  25. Multi-Component Diaphragm (MCD)Test Fixture • Performance of the connected precast units subjected to a combination of shear, axial load, and flexure across key portions of joints between precast units Engineering Research Center PCI Committee Days April 2003

  26. Experimental Program at Lehigh University • Full-scale Components (Full-width 10ft.) • Double Tee and Hollow Core Panels • Topped and Untopped • Quasi-Static Loading • Baseline Tests • Pure shear / axial force • Monotonic and Cyclic • Single and multiple connector • Diaphragm Panel-Panel Tests • High shear and flexure regions (predetermined cyclic) • Multiple Panel Tests • High shear, tension, and flexure loading (from analysis) 1-1 Engineering Research Center PCI Committee Days April 2003

  27. Integration and Flow of Research Activities 1 4 2a 2 3a 3

  28. Proposed Research Schedule

  29. 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.

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