Seismic Design Methodology for Precast Concrete Floor Diaphragms

Seismic Design Methodology for Precast Concrete Floor

Diaphragms

Research to Practice WebinarApril 23, 2012

Sponsored by the Earthquake Engineering Research Institute (EERI) and the Network for Earthquake Engineering

Simulation (NEES)

Dr. Ned M. Cleland, P.E Dr. Robert B. Fleischman Dr. S.K. Ghosh, P.E. Blue Ridge Design, Inc University of Arizona SKG Associates

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April 23 2012PCI/NSF/CPFPART 1:2 of 34

OutlineOutline

Introduce PCI/NSF/CPF DSDM Research Effort Review Key Behaviors of Precast

Diaphragms and Design Philosophy Adopted Summarize DSDM Research Project Findings Present Precast Diaphragm Design

Procedure Cover Precast Diaphragm Design Example Discuss Codification Efforts

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Diaphragm Action

Diaphragm action is intended to carry seismic forces horizontally in the floor slab to walls and frames…

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Precast floors can be vulnerable due to the need to transfer forces at discrete locations across floor joints between precast panels

Dry Chord Connection

Dry Chord Connection

Web Connection

Slug

Faceplate

Anchorage Bars

Panel-To-Panel Web Connection

Field Topped Pre-Topped

Web Connection

Precast Diaphragm Details

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Precast Diaphragm Past Performance

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DSDM Project

Objective: Develop an industry endorsed seismic design methodology for precast concrete diaphragms.

Scope: Untopped and topped composite precast floor diaphragms.

Project Co-funders: CPF, PCI and NSF

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DSDM Consortium

Producer Members

University of CaliforniaSan Diego

Jose’ Restrepo, PI

Producer Members

Lehigh UniversityClay Naito, PI

Richard Sause, Co-PI

Industry Advisory Panel

Industry LiaisonS. K. Ghosh, Co-PI

University of ArizonaRobert FleischmanConsortium Leader

DSDM Task Group

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DSDM Task Group

S.K.GhoshDSDM Task Group Chair

President, S. K. Ghosh Associates

R. BeckerVice President

Spancrete Industries, Inc.

N. ClelandPresident

Blue Ridge Design, Inc.

Tom D’ArcyPresident

Consulting Engineers Group

N. HawkinsProfessor Emeritus

Univ. of Illinois

Paul JohalResearch Director

PCI

Joe MaffeiEngineering ConsultantRutherford & Chekene

Engineers

Susie NakakiPresident

The Nakaki Bashaw Group, Inc.

Doug SuttonProfessor

Purdue University

Harry GleichVice President

Metromont Prestress

Dave DieterVice-President

MidState Precasters

Industry Task Group

Chuck MagnesioVice-President

JVI, IncDichuan Zhang, Ge Wan, Michael Mielke, Alicia

Mullenbach, Univ. of Arizona

Liling Cao, Rui Ren, Wesley Peter, Lehigh Univ.

Matt Schoettler and Andrea Belleri, UCSD

Graduate Researchers

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An aspect of diaphragm behavior not elucidated in the codes is the relationship of the design forces used in equivalent lateral force (ELF) procedures to the inertial forces that may actually develop in floors during a seismic event.

Diaphragm Forces

Fleischman and Farrow, Eq. Eng & Struc. Dyn, 2001

Diaphragm peak inertial forces may significantly exceed current design values

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The presence of large inertial forces can be critical in precast floor systems:

Current Design Code

In combination with complex load paths in floor systems, can lead to inelastic diaphragm action.

Inelastic deformation demands in precast diaphragms will tend to concentrate in the joints between precast units, and only at certain joints.

These demands can exceed the deformation capacity of reinforcing details developed without this consideration, leading to a nonductile diaphragm failure.

High diaphragm flexibility due to the inherently less stiff jointed system, in long floor spans where precast is used effectively, could lead to excessive drift of gravity system columns

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eFpx

Elastic Design Option (EDO)

Maximum Force Demand

Diaphragm force

Diaphragm lateral displacement

forceforce

L

d

L

d

VV

MMCurrent design force Fpx

Possible Nonductile Response

(MCE)Amplified

design force

Diaphragm Design Approach

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DBE force demand

DFpx

Elastic design optionDiaphragm force


Current designFpx

MCE ductility demand

DSDM Design Philosophy

Basic Design Option (BDO)

Amplified design force

force

Capacity Design

Shear Failure

Chord Failure

vDFpx

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Elastic design optionDiaphragm force


Current design force Fpx

rFpx


Reduced Design Option (RDO)

Yields in DBEWithin allowable deformation limits in MCE

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EDODiaphragm force


Current design force Fpx

RDO

LDE MDEHDE

Connector Classification

BDO


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DSDM Research Flow

Diaphragm Level (UA)

Capacity Design Factors.

Internal Force Paths

Structure Level (UCSD)

Diaphragm seismic force

Diaphragm flexibility limits

FpxFpxFpx

FE Pushover Analysis 3D FE Dynamic Analysis

MDOF Dynamic Analysis

Detail Level (LU)

Characteristics of diaphragm details

Connection classification

Full-Scale Detail Tests

Scaled Shake Table Test

Hybrid Testing of Joints

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Precast Diaphragm Connector Testing

Classify connectors:

Low Defo (LDE)

Mod Defo (MDE)

High Defo (HDE)

Connection Details Evaluation

Previous Test Results Evaluation

Experimental

Analytical

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-80

-40

0

40

-0.2 0 0.2 0.4 0.6 0.8

dt (in)

T (kips)

Test

Model

Modeling of Chord Connector

=0.7

T Td

t

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Modeling of JVI Connector

dv

V V

Cyclic response

-20

-10

0

10

20

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

dv (in)

V(k

ips)

TEST

-20

-10

0

10

20

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

Model

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Modeling of Ductile Mesh

V, dv

-50

-25

0

25

50

-1.5 -1 -0.5 0 0.5 1 1.5

dv(in)

V (

kips

)

Test

-50

-25

0

25

50

-1.5 -1 -0.5 0 0.5 1 1.5

Model

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Discrete FE models

Diaphragm Analytical Modelling

Ramp Cavity

Transverse inertial load Precast units

Nonlinear coupled springs and contact elements

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Prototype Structure #1: Parking Garage

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PDH Test

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PDH Test Results: Flexure

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

-0. 0002 -0. 0001 0 0. 0001 0. 0002

rot

M (k

-in)

TestPredi ct

-8000

-6000

-4000

-2000

0

2000

4000

6000

-0. 0002 0 0. 0002 0. 0004 0. 0006 0. 0008

rot

M (k

-in)

TestPredi ct

-8000

-6000

-4000

-2000

0

2000

4000

6000

8000

-0. 0015 -0. 001 -0. 0005 0 0. 0005

rot

M (k

-in)

TestPredi ct

-6000

-4000

-2000

0

2000

4000

6000

-0. 0005 0 0. 0005 0. 001 0. 0015

rot

M (k

-in)

TestPredi ct

-10000

-8000

-6000

-4000

-2000

0

2000

4000

6000

8000

-0. 004 -0. 003 -0. 002 -0. 001 0 0. 001

rot

M (k

-in)

Predi ctTest

CH Service CH DBE CH MCE

CH Bi-dir DBE BK MCEJoint Flexural

Response

M

M

Weld Fracture

Minor Cracking

Major Cracking/Crushing

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Shaking Table Structure

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Test Comparison: Knoxville

Knoxville DBEδ

- 0. 8

- 0. 6

- 0. 4

- 0. 2

0

0. 2

0. 4

0. 6

0. 8

4 5 6 7 8 9

Ti me (s)

D(in

)

TestPredi ct i on

Diaphragm midspan roof drift

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Phase III: Design Methodology Development

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Modeling of Evaluation Structure

Precast units: Plane stress element

Chord connector: Nonlinear springs

Shear connector: Nonlinear springs

Symmetryboundary

Column: 3D beam element

Spandrel: 2D beam element

Connector Elements

Moment frame 3D beam element

Shear wall3D shell element

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Suite of Ground Motions

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

0 10 20 30 40

Time (s)

A (

g)

BK1BK2BK3BK4BK5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0 10 20 30 40 50

Time (s)

A (

g)

KN1

KN2

KN3

KN4

KN5

0

0.2

0.4

0.6

0.8

1

0 0.4 0.8 1.2T (s)

Sa (g)

MeanDesignN-6N-4N-2

Tflx

Trig

SDC E

SDC C

0

0.5

1

1.5

2

2.5

3

0 0.4 0.8 1.2

T (s)

Sa (g)

DesignMeanN=6N=4N=2

Trig,SW

Trig,FR

Tflx,SW

Tflx,FR

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-0.2 0 0.2 0.4 0.6-600

-400

-200

0

200

400

600

Opening (in)

T (

k)

Ψ = 1.0Ψ = 1.5Ψ = 2.0Ψ = 2.5

Trial Design Factors

Chord connector

SDC E AR=3

T, δ

T

δ

Diaphragm Force Amplification Factor

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Design Methodology Verification: Prototype Structures

Lbeam=48' L'=204' 48'

L=300'

60'

d=60'

60'

a=180'

25'8'

Lite wall

Shear wall

b=12'

Ramp Span Transverse

Longitudinal

North

South

RampLanding

Joint #: 1 2 3 4 5 6 7 8 9 10 11 12

West South

North East

16'

10'-6"

10'-6"

10'-6"

47'-6"

204'

4-Story Parking Structure

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230'

147'

170'

South

North

West East

24.5'

24.5'

20'30'Joint # 1 2 3 4 5 6 7 8 9 10 11

30' 20' 20' 20' 20' 30'30' 30' 30'

230'

15'

106'

13'

15'

13'

13'

13'

13'

13'

13'

Design Methodology Verification: Prototype Structures

8-Story Office Building

Seismic Design Methodology for Precast Concrete Floor Diaphragms

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