Development of a Diaphragm Seismic Design Methodology (DSDM) for Precast Concrete Structures Robert Fleischman and Ge Wan, University of Arizona Clay Naito, Richard Sause and Liling Cao, Lehigh University José Restrepo and Matt Schoettler, UC-San Diego S.K. Ghosh, S.K. Ghosh Associates, Inc.

Outline of Presentation Background History Background History Rationale for NEES-type Research Research Approach Industry Interaction Year 1 Activities

Problem Statement The precast concrete industry has mounted a sustained effort to develop seismic-resistant lateral force resisting elements. NSF PRESSS program

1994 Northridge earthquake Problem Statement However, the poor performance of precast concrete diaphragms in recent earthquakes underscores the importance of examining the entire precast structural system. 1994 Northridge earthquake

PCI Solicitation and Award In October 2002, PCI distributed an RFP for the development of a comprehensive seismic design methodology for floor diaphragms in precast concrete buildings. A multi-university research team comprised of investigators from the University of Arizona (UA), University of California at San Diego (UCSD), and Lehigh University (LU) was selected.

* Participated in proposal stage only. DSDM Consortium PCI, IAP * DSDM Task Group * Participated in proposal stage only.

Producer Members Blakeslee Prestress, Inc. High Concrete Structures Precast/Prestressed Concrete Manufacturers Association of California Spancrete, Inc. Tindall-Virginia Ivy Steel & Wire Metromont Prestress

NSF Funding Proposal submitted to National Science Foundation (NSF) in 2003. Precast Industry Contribution: $200,000 in direct funding $60,000 in travel and logistical support $75,000 for consulting services $91,000 in specimen donations Requested budget: approximately $500,000 DSDM Consortium awarded NSF grant in 2004.

Project Objective and Scope Develop a Seismic Design Methodology for Precast Concrete Diaphragms including: Topped and Pretopped Diaphragms Hollow Core and Double Tees Precast Units Low to High Seismic Zones Existing and Promising Reinforcement Details

Outline of Presentation Background History Rationale for NEES-type Research Rationale for NEES-type Research Research Approach Industry Interaction Year 1 Activities

Challenges in developing a DSDM Floor Inertial Loads Equivalent lateral force (ELF) design procedures currently in use may significantly underestimate diaphragm inertial forces. After Fleischman and Farrow, EQ Spectra 2001; also see Rodriguez and Restrepo EE & SD 2002, Eberhard and Sozen, Miranda, etc.

Discretely connected units Challenges in Developing a DSDM Jointed Diaphragms Precast diaphragms possess several characteristics that make a DSDM challenging: Complex Force Paths Long floor spans Fpx -0.6 0.6 -25 Discretely connected units

Challenges in developing a DSDM Inelastic deformations and diaphragm flexibility Deformation patterns that may cause complex internal force combinations. Large inter-story drifts away from primary LFRS elements. High localized deformation. demand in joints between precast units due to twist. After Fleischman and Farrow, EQ Spectra 2001; EE & SD 2000

Challenges in developing a DSDM The diaphragm seismic response shown is a complex interaction of : System behavior (the overall structure) Component behavior (the floor diaphragms) Section behavior (diaphragm panels and joints) Detail behavior (individual hardware/reinforcement) Previous research attempts have typically focused on only one of these particular “levels” at a time.

Previous “System-Level” Research 2D (in the plane of the floor) Finite Element (FE) models of the floor diaphragm are analyzed for capacity using nonlinear pushover techniques. The diaphragm characteristics (stiffness, strength, ductility) obtained are used to create simple structural models to obtain demands (forces, drift, ductility) under seismic loading. Diaphragm forces and force paths estimated entirely through analytical simulation The analytical simulations in turn depend heavily on tests of individual joint reinforcing details under highly idealized loading conditions.

Outline of Presentation Background History Rationale for NEES-type Research Research Approach Research Approach Industry Interaction Year 1 Activities

Integrated Analysis and Experimentation Research Approach: Integrated Analysis and Experimentation (EQ) Demand Verified By Capacity UA Analyses link UCSD structure test with LU detail tests. Load Input Model Input

Outline of Presentation Background History Rationale for NEES-type Research Research Approach Industry Interaction Industry Interaction Year 1 Activities

DSDM Task Group Set the physical scope Selection of prototype structures and representative details 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 Doug Sutton Professor Purdue University Paul Johal Research Director PCI Joe Maffei Engineering Consultant Rutherford & Chekene Engineers Susie Nakaki President The Nakaki Bashaw Group, Inc. Harry Gleich Vice President Metromont Prestress

Prototype Structures PS#1: 4-story side-by-side parking garage PS#2: 4-story helical parking garage Distributed shear walls PS#1: 4-story side-by-side parking garage Ramp Perimeter shear walls PS#5: two-way moment frame parking deck PS#3: 5-story L-wing office building Distributed cores PS#4: 4-story office building/school Central core

Seismic Design Sites Candidates sites selected by DSDM TG Moderate High Near Field Soft Soil

Prototype Structure Design PS#1: Moderate Seismic Zone (Knoxville) Vertical distribution Design Code IBC 2003 Ss 0.58 S1 0.147 Soil Site Class C Fa 1.17 Fv 1.65 Sms= Fa Ss 0.68 Sm1= Fv S1 0.24 SDS= 2/3 Sms 0.45 SD1= 2/3 Sm1 0.16 EW Shear Walls R=5, W0=2.5, Cd=4.5 NS Light Framed Walls R=4.5, W0=2.5, Cd=4 Seismic Design Category C Cs 0.09 Cs,min 0.0198 Cs,max 0.0589 Base shear 1470 kips Diaphragm design Collectors Chord Steel Shear Reinf

Representative Diaphragm Details Primary diaphragm details (web, chord, collector, wall anchorage) DT/Spandrel (PS#3) DT/IT (PS#1) IT/Wall (PS#1) Spandrel/Col. (PS#1) Secondary details (spandrels, floor beams, columns) DT chord (PS#1) DT web (PS#2) DT/Wall (PS#2) DT along Wall (PS#2)

Outline of Presentation Background History Rationale for NEES-type Research Research Approach Industry Interaction Year 1 Activities Year 1 Activities

Integration and Flow of Activities 1 2 1 4 2a 2 Diaphragm Characteristic 3a 3

Nonlinear spring and contact elements in ANSYS Analytical Program: Diaphragm FE Model Nonlinear spring and contact elements in ANSYS 2D FE model: PS#1 Properties based on test data of details Year 1: existing tests Year 2: LU test

JVI, Concrete Technology Co., Dayton; Venuti, Oliva, et.al. Lehigh Database Monotonic Shear Response cover plate JVI, Concrete Technology Co., Dayton; Venuti, Oliva, et.al.

Combined Forces on Connectors Ratio of shear to tension in the web reinforcement.

Combined Force Tests Effect of Tension and Cycling on Shear Response: (Oliva 98) Monotonic Shear with Tension Cyclic vs. Monotonic Shear

Project Year 1: Lehigh University (LU) Tests The three actuator load frame built at LU possesses the ability to provide proportional and non-proportional loading under mixed mode (displacement or force) control. Test setup Loading protocol

Representative Detail Building the Diaphragm Model Representative Detail LU test “A” Test Model Plastic link elements to match monotonic tension. Contact Element Nonlinear shear spring to supplement shear strength T V Hairpin

Connector Element Calibration Comparison w/ M. Oliva’s test results U-Wisc Mad (1998) Angled bars T V

Cyclic Shear Comparison Plate w/rebar (Oliva 1998) µ=1 µ=1.5 µ=2 T V

Project Year 1: UCSD Shaking Table Test Structural level examination: Table Outrigger Platen 1:2 to 1:3 scale model 3-story specimen to include 3 floor systems: Untopped double tee Topped double tee Hollow core

Overall Project Objective An effective seismic design methodology for precast concrete diaphragms: Accurate Design Forces Method for Estimating Internal Forces Stiffness Calculations Limits on Diaphragm Flexibility Knowledge of Detail Capacities Structural Integrity Detailing

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