Dominic Kelly, SE · 2018-04-04 · 1964 Anchorage Alaska Earthquake Inadequate shear transfer from diaphragm to walls Warehouse 21- 884, Elmendorf AFB Photo Source: University of

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Seismic Design of Rigid Wall-Flexible Diaphragm Buildings: An Alternate Procedure FEMA P1026 (expected 3/2015)

Dominic Kelly, SE Principal Simpson Gumpertz & Heger Inc.

NEHRP/Building Seismic Safety Council Colloquim Presented February 11, 2015

“Rigid Wall – Flexible Diaphragm” (RWFD) Structures

“Big-Box” Retailers (Walmart, Target, Home Depot…)

Distribution Centers (Warehouses, Logisitics…)

Concrete or Masonry Walls Relatively Rigid In-plane

Wood or untopped Steel Deck Diaphragms Relatively Flexible In-plane

Source: The Palmer Company

Rigid Wall – Flexible Diaphragm (RWFD) Structures

Warehouses & “Big-Box” retailers

Concrete or masonry walls

Wood or steel deck diaphragm

Rigid Wall – Flexible Diaphragm (RWFD) Structures

Add a couple of representative RWFD building photos

Source: John Lawson

RWFD Behavior Diaphragm – Large Deformations (Long Period)

Shear Walls – Small Deformations (Short Period)

∆𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤

∆𝑑𝑑𝑑𝑑𝑤𝑤𝑑𝑑𝑑

∆𝐷𝐷𝑑𝑑𝑤𝑤𝑑𝑑𝑑≫ ∆𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤

From Anchorage to Napa Primarily out-of-plane wall anchorage failures Current wall anchorage force levels have not

experienced strong ground motions yet. Primarily tilt-up, but some masonry

Inventory primarily tilt-up

Primarily wood diaphragm, but some steel Inventory primarily wood

Performance of RWFD Buildings in Previous Earthquakes

RWFD Performance 1964 Anchorage Alaska Earthquake

Inadequate shear transfer from diaphragm to walls

Photo Source: University of Alaska, Fairbanks Warehouse 21-884, Elmendorf AFB (Tilt-up, steel frame, 2x wood sheathing.)

RWFD Performance 1971 San Fernando Earthquake

Inadequate wall anchorage

Photo Credit: Los Angeles City Dept of Building & Safety

1992 Landers Earthquake Inadequate wall and collector anchorage.

Photo Source: California Seismic Safety Commission

9

RWFD Performance 1994 Northridge Earthquake


Photo Source: Doc Nghiem



Photo Credit: Cascade Crest Consulting Engineers



Photo Courtesy of EERI

Evolution of Wall Anchorage Req’ts

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

Sei

smic

Coe

ffic

ient

(Str

engt

h)

UBC/IBC Edition Wall Anchorage Forces (Strength-Level)

San Fernando Loma Prieta Northridge

Wall ties & cross ties req’d. No wood crossgrain bending

Subdiaphragms

3x wood min Concentrically loaded & Special pilasters rules

Zone 4 SDS=1.0 SD1=0.6

Wood, Conc., Masonry

Steel elements

Landers

Future RWFD Performance Wall anchorage issue solved?

Inelastic response may now shift to diaphragm

New Research Initiative

Funded by FEMA

Directed by BSSC

Research conducted by

Dominic Kelly Andre Filiatrault Maria Koliou

John Lawson

New Research Initiative

Objective for Simplified Seismic Design Project: • Explore creating standalone provisions for “box”

buildings with flexible diaphragms and stiff vertical elements of the SFRS.

• Develop an alternate design approach and provisions for this type of building.

Added benefit for RWFD project: • Measured response demonstrates that the response

to earthquake ground motion is dominated by the response of the diaphragm.

• Current code provisions are based on the vertical system dominating the response.

Project Working Group 3 Initiative

17

Alternate Design Approach Develop separate TDiaph, RDiaph, ΩDiaph

For use in ASCE 7’s Equivalent Lateral Force Procedure Validate with FEMA P695

Apply a two-stage analysis procedure

Model after ASCE 7’s 12.2.3.2 Similar to podium style buildings

Alternate Design Approach

Classic Structural Response Model

Current Design Practice

Shear Wall

Diaphragm

Two-Stage Response Model

Alternate Design Procedure

R T

RDiaph TDiaph

RWall TWall

Numerical Model Development of a non-linear model

Inelastic connector response Global inelastic shear, flexure, P∆ Highly efficient

Evaluation of current practice:

50 different archetypes x 22 ground motions x 2 components x 20 seismic intensities = 44,000 IDAs

“Numerical Framework for Seismic Collapse Assessment of Rigid Wall-Flexible Diaphragm Structures” by Maria Koliou, et. al., 10NCEE

Building Archetypes Two Diaphragm Material Archetypes

Wood Structural Panel (nails)

Building Archetypes Connector Archetypes

Structural Wood Panel Common Nails (smooth finish)

Photo Credit: John Lawson

Building Archetypes Two Diaphragm Material Archetypes

Steel Decking (welds, screws, PAFs, BP)

Building Archetypes Connector Archetypes

Steel Decking Welds (spot & seam) PAFs Screws Button Punch

Photo Credits: Massarelli, 2010

Evaluation Using FEMA P695 Collection of representative archetypes

Performance

Group 1 2 3 4 5 6 7 8 9 10 11

Diaphragm Construction Wood Structural Panel Steel Deck

Seismic Design Load

Level SDC Dmax SDC Cmax SDC Dmax SDC Cmax

Building Size Large Small Large Small Large Small Large Small

Connectors Nail Nail Nail Nail Weld/BP PAF’s & Screws/ Screws

Weld/BP PAF’s & Screws/ Screws

PAF’s & Screws/ Screws

Weld/ Weld

PAF’s & Screws/ Screws

Numerical framework based on a three step sub-structuring modeling approach: Step 1: hysteretic response database for roof diaphragm connectors

Step 2: Inelastic diaphragm model incorporating local hysteretic connector responses

Step 3: Simplified building model incorporating global hysteretic diaphragm model responses

Numerical Framework

-1 -0.5 0 0.5 1-300

-200

-100

0

100

200

300

400

Displacement (inches)

Forc

e(lb

s)

est

Connector Database Diaphragm model

V

V

xr4 –xr3

V

xr3 –xr2

V

xr2 –xr1

V

xr1

Simplified Building Model

md2

md3

xiw

xd1xd2

xd3xd4

md1 miw

xd5

md5

kd5kd4

kd3kd2

kd1

kiw

md4

Step 1 Step 2 Step 3

Step 3: Simplified building model dfsggdsgdgdf

Numerical Framework

S

Horizo of in-p

md2

md3

xiw

xd1xd2

xd3xd4

mpwi,j Mass for out-of-plane walls

md1 miw

xd5

md5

Xd,i DOF for roof diaphragm

Xiw DOF for in-plane walls md,i Mass for roof diaphragm

miw Mass for in-plane walls

Xpw i,j DOFs for out-of-plane walls

Typical horizontal inelastic roof diaphragm springs (Wayne-Stewart hysteresis)

Horizontal linear elastic spring of in-plane walls

Typical series of vertical beam elementssimply supported@ top & bottom

kd5kd4

kd3kd2

kd1

kiw

md4

Evaluation Using FEMA P695 PERIOD COMPARISONS

Wood diaphragm

span length High-seismic archetypes

Moderate-seismic archetypes

ASCE 7-10 Equation 12.8-7

400 ft 0.85 to 0.87 sec 0.90 to 0.92 sec 0.26 sec



Steel diaphragm span length




Proposed fundamental period formula for RWFD buildings with wood diaphragms:

h is the height of the in-plane shear wall in ft.

L is the span of the roof diaphragm in ft.

hC

LTW

0019.0002.01 +=

RWFD Behavior

Shear Wall (ASCE 7 §12.8-9)

Wood Diaphragm

hC

LTW

0019.0001.01 +=Steel Diaphragm

Diaphragm

Evaluation Using FEMA P695 Wood Archetype Period Comparisons

Evaluation Using FEMA P695 Steel Archetype Period Comparisons

Performance evaluation – Wood Diaphragms

P695 Evaluation of Current Design Approach

Building Size

Diaphragm Aspect Ratio

Diaphragm Construction

Seismic SDC

CMR μΤ SSF ACMRAccept. ACMR

Pass/Fail

HWL_21_N_OSB_RW4_07 Large 2:1 Wood Dmax 1.89 8.07 1.43 2.70 1.73 PassHWL_12_N_OSB_RW4_02 Large 1:2 Wood Dmax 2.24 8.95 1.36 3.05 1.73 PassHWL_11_N_OSB_RW4_01 Large 1:1 Wood Dmax 1.60 8.42 1.43 2.29 1.73 Pass

1.91 8.48 1.41 2.68 2.30 Pass

HWS_21_N_OSB_RW4_01 Small 2:1 Wood Dmax 1.40 7.20 1.31 1.84 1.73 PassHWS_12_N_OSB_RW4_01 Small 1:2 Wood Dmax 1.76 8.95 1.36 2.39 1.73 PassHWS_11_N_OSB_RW4_01 Small 1:1 Wood Dmax 1.55 8.32 1.36 2.10 1.73 PassHWS_11_N_OSB_RW4_02 Small 1:1 Wood Dmax 1.55 8.51 1.36 2.10 1.73 Pass

1.57 8.25 1.35 2.11 2.30 Fail

MWL_21_N_OSB_RW4_01 Large 2:1 Wood Cmax 2.48 8.15 1.44 3.57 1.73 PassMWL_12_N_OSB_RW4_01 Large 1:2 Wood Cmax 2.33 8.79 1.35 3.15 1.73 PassMWL_11_N_OSB_RW4_01 Large 1:1 Wood Cmax 2.12 8.54 1.45 3.08 1.73 Pass

2.31 8.49 1.41 3.27 2.30 Pass

MWS_21_N_OSB_RW4_01 Small 2:1 Wood Cmax 1.50 8.05 1.16 1.74 1.73 PassMWS_12_N_OSB_RW4_01 Small 1:2 Wood Cmax 1.72 8.49 1.14 1.96 1.73 PassMWS_11_N_OSB_RW4_01 Small 1:1 Wood Cmax 1.96 8.09 1.14 2.23 1.73 Pass

1.73 8.21 1.15 1.98 2.30 Fail

Mean of Performance Group:Performance Group No. PG-4E (Wood, Small Building, Existing Design)

Mean of Performance Group:

Performance Group No. PG-2E (Wood, Small Building, Existing Design)

Mean of Performance Group:Performance Group No. PG-3E (Wood, Large Building, Existing Design)

Collapse Margin Parameters Acceptance Check

Performance Group No. PG-1E (Wood, Large Building, Existing Design)


Archetype ID

Design Configuration

Performance evaluation – Steel Diaphragms (SDC Dmax)

P695 Evaluation of Current Design Approach

Building Size

Diaphragm Aspect Ratio

Diaphragm Construction

Seismic SDC

CMR μΤ SSF ACMRAccept. ACMR

Pass/Fail

HSL_21_W_WB_RW4_01 Large 2:1 Steel Dmax 0.99 8.09 1.34 1.33 1.73 FailHSL_12_W_WB_RW4_01 Large 1:2 Steel Dmax 1.90 8.26 1.33 2.53 1.73 PassHSL_11_W_WB_RW4_01 Large 1:1 Steel Dmax 0.95 8.16 1.33 1.27 1.73 Fail

1.28 8.17 1.33 1.71 2.30 Fail

HSL_21_P_S_RW4_01 Large 2:1 Steel Dmax 1.23 8.24 1.35 1.67 1.73 FailHSL_12_P_S_RW4_01 Large 1:2 Steel Dmax 2.07 8.14 1.33 2.75 1.73 PassHSL_11_P_S_RW4_01 Large 1:1 Steel Dmax 1.13 8.26 1.36 1.53 1.73 FailHSL_11_S_S_RW4_01 Large 1:1 Steel Dmax 1.15 8.01 1.33 1.53 2.73 Fail

1.40 8.16 1.34 1.87 2.30 Fail

HSS_11_W_B_RW4_01 Small 1:1 Steel Dmax 1.73 7.94 1.32 2.28 1.73 PassHSS_21_W_B_RW4_01 Small 2:1 Steel Dmax 1.42 8.05 1.33 1.89 1.73 PassHSS_12_W_B_RW4_01 Small 1:2 Steel Dmax 1.90 7.91 1.32 2.51 1.73 Pass

1.68 7.97 1.32 2.23 2.30 Fail

HSS_11_P_S_RW4_01 Small 1:1 Steel Dmax 1.55 8.02 1.33 2.07 1.73 PassHSS_11_S_S_RW4_01 Small 1:1 Steel Dmax 1.43 8.15 1.33 1.91 1.73 PassHSS_21_P_S_RW4_01 Small 2:1 Steel Dmax 1.33 8.33 1.33 1.76 1.73 PassHSS_12_P_S_RW4_01 Small 1:2 Steel Dmax 1.71 8.25 1.33 2.27 1.73 PassHSS_21_S_S_RW4_01 Small 2:1 Steel Dmax 1.25 7.85 1.32 1.65 1.73 FailHSS_12_S_S_RW4_01 Small 1:2 Steel Dmax 1.42 8.06 1.33 1.89 1.73 Pass

1.45 8.11 1.33 1.92 2.30 Fail

Mean of Performance Group:Performance Group No. PG-8E (Steel, Small Building, Screws as sidelap Connectors, Existing Design)


Performance Group No. PG-6E (Steel, Large Building, Screws as sidelap Connectors, Existing Design)

Mean of Performance Group:Performance Group No. PG-7E (Steel, Small Building, Button Punches as sidelap Connectors, Existing Design)

Collapse Margin Parameters Acceptance Check

Performance Group No. PG-5E (Steel, Large Building, Welds and Button Punches as sidelap Connectors, Existing Design)


Archetype ID

Design Configuration

Future Design Paths for RWFD Buildings

Path 1 - Yielding mechanism not clearly defined Close to current design

Path 2 - Yielding Diaphragm - Alternate Design Procedure Focus of remainder of talk Rectangular wall segments Wood diaphragm (steel industry to work on

resolving issues identified in diaphragm tests) Path 3 - Yielding wall system

Alternate Design Methodology

Classic Structural Response Model

Current Design Practice

Shear Wall

Diaphragm

Two-Stage Response Model


R T

RDiaph TDiaph

RWall TWall

Alternate Design Procedure Apply a two-stage analysis procedure


= +

Alternate Design Procedure Apply a two-stage analysis procedure


+

Rflex Tflex

Rrigid Trigid

Fp-flex

𝐹𝐹𝑑𝑑 = 𝐹𝐹p−flex𝑅𝑅𝑟𝑟𝑑𝑑𝑟𝑟𝑑𝑑𝑑𝑑 𝜌𝜌𝑟𝑟𝑑𝑑𝑟𝑟𝑑𝑑𝑑𝑑⁄𝑅𝑅𝑓𝑓𝑤𝑤𝑓𝑓𝑓𝑓 𝜌𝜌𝑓𝑓𝑤𝑤𝑓𝑓𝑓𝑓⁄

(Only amplify)

Alternate Design Procedure Develop separate TDiaph, RDiaph, ΩDiaph

For use in ASCE 7’s Equivalent Lateral Force Procedure Table values (developed and validated from FEMA P695)

Rwall Twall

RDiaph TDiaph

Alternate Design Procedure Resolve Issues with Current Procedure

Inadequate margins against collapse in diaphragm.

Diaphragm size matters

Two portions of building have different behaviors

Inelastic response localized at diaphragm boundary

Evaluate with RDiaph

Evaluate with TDiaph

Encourage distributed inelastic behavior

Conduct two-stage analysis

Alternate Design Procedure Two-stage analysis procedure

1. Diaphragm design

Diaphragm period Tdiaph for seismic response

RDiaph = 4.5 instead of 4 1.5x overstrength at boundaries (10% each end)

2. Shear wall design

Adjusted diaphragm loads R and T from ASCE 7

Validate with FEMA P695

based on

Strong Perimeter Concept Create a zone of 10% of the diaphragm width

or length along the diaphragms perimeter yielding extends deeper into the diaphragm Better subdiaphragm strength for top of wall support

Design Approach Rdiaph = 4.5 in middle zone and force is amplified by 1.5 in edge

zone

Based on V for Rdia = 4.5 V amplified 1.5x

0.1L 0.1L 0.8L

9 ¼” Concrete Wall Panels, typ.

15/32” Structural I OSB with staggered layout

2x4 DF #2 subpurlins at 24” o.c.

Steel Joists at 8-ft o.c.

56’-0” 56’-0” 48’-0” 48’-0” 48’-0” 48’-0” 48’-0” 48’-0”

50’-

0”

50’-

0”

50’-

0”

50’-

0”

Example Archetype

43

1 2 2 3 4 5 6 5 4 3 6

1

2

3

4

5

6

10d at 6,6,12

10d at 4,6,12

10d at 2½,4,12

10d at 2,3,12 w/ 3x framing

2 lines of 10d at 2½,4,12 w/ 4x framing


32’ 32’ 32’ 32’ 24’ 96’ 24’ 32’ 32’ 32’ 32’

20’

20’

160’

ASCE 7-10 Diaphragm Nailing

44

6 1 3 6 4 5 5 4 3 6

1

2

3

4

5

6

10d at 6,6,12

10d at 4,6,12

10d at 2½,4,12

10d at 2,3,12 w/ 3x framing



32’ 32’ 32’ 32’ 24’ 96’ 24’ 32’ 32’ 32’ 32’

20’

20’

160’


Weaken interior & strengthen boundary

2 2

45

Distributed Inelastic Behavior

Median ductility distribution using the FEMA P695 ground

motions at MCE intensity

400’x200’ Wood Structural Panel Diaphragm

– short direction excitation

200’x400’ Wood Structural Panel Diaphragm

– long direction excitation

𝜇𝜇 =∆𝑢𝑢𝑤𝑤𝑢𝑢𝑑𝑑𝑢𝑢𝑤𝑤𝑢𝑢𝑓𝑓∆𝑦𝑦𝑑𝑑𝑓𝑓𝑤𝑤𝑑𝑑


-0.4 -0.2 0 0.2 0.4 -5000

0

5000

0

0

0

-0.4 -0.2 0 0.2 0.4 -5000

0

5000

0

0

0

0

0

0

0

0

0

0

0

0

0

x=0 m

Center of roof diaphragm

x=3.81 m

x=11.43 m

x=19.05 m

x=26.67 m

x=34.29 m

x=41.91 m

x=49.53 m

x=57.15 m

x=60.96 m

µ= 3.9

µ= 3.4

µ= 1.2

µ= 1.0

µ= 1.0

µ= 2.9

µ= 2.5

µ= 1.8

µ= 1.4

µ= 1.2

µ= 1.05

µ= 1.0

µ= 1.0

µ= 1.0

Displacement [m] Displacement [ m ]

µ= 1.0

µ= 1.0

µ= 1.0

µ= 1.0

Center of roof diaphragm Hysteretic diaphragm

response for Friuli, Italy (1976)

Record scaled to MCE intensity

(a) Conventional (ASCE 7-10) diaphragm design

(b) Distributed yielding diaphragm design

400’x200’ wood structural panel diaphragm – short

direction excitation

Localized Inelastic Behavior

In tall buildings, collapse is more likely if yielding is concentrated

in only a few joints.


Collapse is less likely if yielding is distributed across more portions of the building.

Goal: Distribute yielding horizontally in diaphragm

Evaluation Using FEMA P695 Same Archetypes but with alternate design

procedure

Evaluation of alternate design methodology: 54 different archetypes x 22 ground motions x 2

components x 2 seismic intensities = 47,520 IDAs

Improved margins against collapse.

Evaluation Using FEMA P695

Performance

group ID

Design Configuration Collapse margin

parameters Pass/

Fail Design

E: Existing

N: New

Building Size Diaphragm

Construction

Seismic

SDC ACMR

Accept.

ACMR

PG-1 E Large Wood Panelized Dmax 2.68

2.30 Pass

N Large Wood Panelized Dmax 3.78 Pass

PG-2 E Small Wood Panelized Dmax 2.11

2.30 Fail

N Small Wood Panelized Dmax 2.52 Pass

PG-3 E Large Wood Panelized Cmax 2.80

2.30 Pass

N Large Wood Panelized Cmax 3.90 Pass

PG-4 E Small Wood Panelized Cmax 1.98

2.30 Fail

N Small Wood Panelized Cmax 3.07 Pass

Evaluation Using FEMA P695

Alternate Design Procedure for RWFD Buildings

is Promising

Design example of current and alternate design procedures are developed and

compared in FEMA P1026

Questions

Documents

Dominic Kelly, SE · 2018-04-04 · 1964 Anchorage Alaska Earthquake Inadequate shear transfer from diaphragm to walls Warehouse 21- 884, Elmendorf AFB Photo Source: University of