Engineering Research Center Development of a Diaphragm Seismic Design Methodology (DSDM) for Precast Concrete Structures Robert Fleischman, Ge Wan and Anuja Kamat, 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.

Engineering Research Center UIUC Structural Engineering Conference April Background History Outline of Presentation Design Challenges Research Approach Industry Interaction Year 1 Activities

Engineering Research Center UIUC Structural Engineering Conference April Problem Statement  The precast concrete industry has mounted a sustained effort to develop seismic-resistant lateral force resisting elements. NSF PRESSS program

Engineering Research Center UIUC Structural Engineering Conference April Problem Statement  However, the poor performance of precast concrete diaphragms in recent earthquakes underscores the importance of examining the entire precast structural system Northridge earthquake

Engineering Research Center UIUC Structural Engineering Conference April PCI Solicitation and Award  Multi-university research team: University of Arizona (UA), University of California at San Diego (UCSD), Lehigh University (LU).  In October 2002, PCI distributed an RFP for the development of a comprehensive seismic design methodology for floor diaphragms in precast concrete buildings.

Engineering Research Center UIUC Structural Engineering Conference April Producer Members Blakeslee Prestress, Inc. High Concrete Structures Precast/Prestressed Concrete Manufacturers Association of California Spancrete, Inc. Tindall-Virginia Ivy Steel & Wire Metromont Prestress

Engineering Research Center UIUC Structural Engineering Conference April DSDM Task Group PCI, IAP * * Participated in proposal stage only. DSDM Consortium NSF-Funded Research

Engineering Research Center UIUC Structural Engineering Conference April 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

Engineering Research Center UIUC Structural Engineering Conference April Design Challenges Background History Outline of Presentation Research Approach Industry Interaction Year 1 Activities

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

Engineering Research Center UIUC Structural Engineering Conference April Fpx Precast diaphragms possess several characteristics that make a DSDM challenging: Challenges in Developing a DSDM Jointed Diaphragms Discretely connected units Complex Force Paths Long floor spans

Engineering Research Center UIUC Structural Engineering Conference April Background History Outline of Presentation Design Challenges Research Approach Industry Interaction Year 1 Activities Research Approach

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

Engineering Research Center UIUC Structural Engineering Conference April Background History Outline of Presentation Design Challenges Research Approach Industry Interaction Year 1 Activities Industry Interaction

Engineering Research Center UIUC Structural Engineering Conference April 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 Paul Johal Research Director PCI Joe Maffei Engineering Consultant Rutherford & Chekene Engineers Susie Nakaki President The Nakaki Bashaw Group, Inc. Doug Sutton Professor Purdue University Harry Gleich Vice President Metromont Prestress

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

Engineering Research Center UIUC Structural Engineering Conference April Seismic Design Sites Candidates sites selected by DSDM TG Moderate High Near Field Soft Soil

Engineering Research Center UIUC Structural Engineering Conference April PS#1: Moderate Seismic Zone (Knoxville) Prototype Structure Design Design CodeIBC 2003 S s 0.58 S Soil Site ClassC F a 1.17 F v 1.65 S ms = F a  S s 0.68 S m1 = F v  S S DS = 2/3  S ms 0.45 S D1 = 2/3  S m EW Shear WallsR=5,  0 =2.5, C d =4.5 NS Light Framed WallsR=4.5,  0 =2.5, C d =4 Seismic Design CategoryC Cs0.09 Cs,min Cs,max Base shear1470 kips Vertical distribution Diaphragm design Chord Steel Shear Reinf Collectors

Engineering Research Center UIUC Structural Engineering Conference April An effective seismic design methodology for precast concrete diaphragms: Research Deliverable  Accurate Design Forces  Method for Estimating Internal Forces  Stiffness Calculations  Limits on Diaphragm Flexibility  Knowledge of Detail Capacities  Structural Integrity Detailing

Engineering Research Center UIUC Structural Engineering Conference April Strength (kips) Diaphragm ConnectionsErection Stability ABCDE Shear Tension Detailing Procedures  Relative strengths

Engineering Research Center UIUC Structural Engineering Conference April 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)

Engineering Research Center UIUC Structural Engineering Conference April Characteristics of Diaphragm Details  Secondary Details: Prototype Structure #

Engineering Research Center UIUC Structural Engineering Conference April Sensitivity Study: Effect of Ramp & Lite Wall Forces on the Ramp Lite Walls Flat Ramp A-A A A (1)(2)(3)(4)(5)

Engineering Research Center UIUC Structural Engineering Conference April Sensitivity Study: Effect of Ramp & Lite Wall Connection Tension Forces at the Lite Wall (max of each pair) ( 1 ) ( 2 ) ( 3 ) ( 4 )( 5 )

Engineering Research Center UIUC Structural Engineering Conference April Background History Outline of Presentation Design Challenges Research Approach Industry Interaction Year 1 Activities

Engineering Research Center UIUC Structural Engineering Conference April Integration and Flow of Activities a 3a 4 Diaphragm Characteristic 1 2

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

Engineering Research Center UIUC Structural Engineering Conference April cover plate JVI, Concrete Technology Co., Dayton; Venuti, Pinchiera, et.al. Lehigh Database Monotonic Shear Response

Engineering Research Center UIUC Structural Engineering Conference April Combined Forces on Connectors Ratio of shear to tension in the web reinforcement.

Engineering Research Center UIUC Structural Engineering Conference April Combined Force Tests Effect of Tension, Cycling on Shear Response (Pinchiera et al 98) Monotonic Shear with Tension Cyclic vs. Monotonic Shear

Engineering Research Center UIUC Structural Engineering Conference April Connector Element Calibration Comparison w/ Pinchiera’s test results U-Wisc Mad (1998) Angled bars T V

Engineering Research Center UIUC Structural Engineering Conference April Diaphragm Sensitivity Studies Nonlinear Pushover Analysis Internal Beam – Typical connection bb VV

Engineering Research Center UIUC Structural Engineering Conference April Diaphragm Sensitivity Studies Individual Connector Response Response of the inner connection Internal Beam – Typical connection

Engineering Research Center UIUC Structural Engineering Conference April Diaphragm Sensitivity Studies Joint Performance Internal Beam – Typical connection

Engineering Research Center UIUC Structural Engineering Conference April Shear, tension status of connections at Failure Web-conn  v :Web-conn  T : Chord yields Diaphragm Sensitivity Studies Diaphragm Performance Internal Beam – Typical connection

Engineering Research Center UIUC Structural Engineering Conference April Parametric Study on Shear Reinforcement Overstrength Determine the relative strength of shear reinforcement w.r.t. chord reinforcement for good performance. Primary objective:

Engineering Research Center UIUC Structural Engineering Conference April Parametric Study on Shear Overstrength Description of the Diaphragm : 60’ 180’ 10’ s s s s/2 s s s s s s s Chord steel

Engineering Research Center UIUC Structural Engineering Conference April Parametric Study on Shear Overstrength V des =1/2F px nVnnVn nV ult Actual flexural yield of diaphragm: M y Contribution of shear reinforcement M b =A s f y d MyMy Diaphragm design force level M des =1/8F px L MbMb Diaphragm shear strength 1/2F px V Diaphragm Pushover Curve Diaphragm lateral displacement Diaphragm flexural strength F px L 1/8F px L M

Engineering Research Center UIUC Structural Engineering Conference April Parametric Study on Shear Overstrength Possible Targets for Shear Overstrength Diaphragm lateral displacement Diaphragm force Maximum demand in a MCE Maximum demand in a DBE Column drift limit Diaphragm design strength (F px ) Ultimate flexural strength (Chord failure) Actual flexural yield of diaphragm 1 st tension failure of connector

Engineering Research Center UIUC Structural Engineering Conference April Pushover curves for diaphragms with different  v (High seismic) No Confinement-Unlimited Tension Capacity

Engineering Research Center UIUC Structural Engineering Conference April Load-deflection histories of individual connectors: (  v =2.06) Deflected shape (a) Connector in high shear region (a) (b) Connector in high tension region (b) (c) Connector subjected to combined forces (c) No Confinement-Unlimited Tension Capacity

Engineering Research Center UIUC Structural Engineering Conference April Parametric Study on Shear Overstrength Parameters to be varied (Phase I): Directly varying parameters:  Shear overstrength (  v )  Shear reinforcement tension deformation capacity (  t,max )  Confinement transverse to the joint L-D relationship of flange-to-flange connector in tension (Pincheira et al)  t,max =0.3 ”  t,max =0.5 ”  t,max = 

Engineering Research Center UIUC Structural Engineering Conference April Comparison of diaphragm pushover curves (  t,max =  and  t,max =0.3”) No Confinement-Limited Tension Capacity

Engineering Research Center UIUC Structural Engineering Conference April Unlimited tension ductility (  t,max =  )  t,chord = 0.56” Scale = 50 Comparison of deflected shapes at same diaphragm displacement  t,chord = 1.51” Scale = 50 Limited tension ductility (  t,max =0.3”) No Confinement-Limited Tension Capacity

Engineering Research Center UIUC Structural Engineering Conference April Integration and Flow of Activities a 3a 4 Diaphragm Characteristic 1

Engineering Research Center UIUC Structural Engineering Conference April  The three actuator load frame built at LU possesses the ability to provide proportional and non-proportional shear and tension loading. Project Year 1: Lehigh University (LU) Tests Loading protocol Test setup

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

Engineering Research Center UIUC Structural Engineering Conference April Lehigh Phase I tests LU test “B” LU test “A” LU test “D” LU test “C” LU test “E” (wwf) LU test “F”

Engineering Research Center UIUC Structural Engineering Conference April Project Year 1: Lehigh University (LU) Tests Tests Result from Shear Displacement only Strength in other tests

Engineering Research Center UIUC Structural Engineering Conference April Integration and Flow of Activities a 3a 4 Diaphragm Characteristic 3

Engineering Research Center UIUC Structural Engineering Conference April Project Year 1: UCSD Shaking Table Test Current configuration of specimen  1:2 scale model  3-story specimen to include 3 floor systems:  Untopped DT  Topped DT  Hollow Core

Engineering Research Center UIUC Structural Engineering Conference April Thank you!