innovative building lateral system with strongback frames and … · 2018-10-01 · •2018 brb, wf...

GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved

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Innovative Building Lateral System with Strongback Frames and Mechanical Fuses

Gregory P. Luth, Ph.D., SE, SECB, GPLAJohn Osteraas, Ph.D., PE, Exponent

SEAONC, August 7, 2018, San Francisco

© 2017 Gregory P Luth & Associates, Inc All rights reserved


The Gigafactory

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• Located in Sparks, Nevada

• Will be world’s largest building by footprint• Approx. 6 million square feet

• ~100 football fields

• Comprised of multiple independent and unique multi-story structures (“modules”)• Each module approx. 500’x500’x70’

• Built in phases • Production began in first phase in 2016

Under construction

G

A’

F’

Under construction


The Challenge

• Must be rapidly designed, detailed, and constructed– Mill order required 7 days after award of structural design contract

• Process design and building layout in continuous state of flux– One, two, or three elevated floor plates of irregular layout and extent

capable of supporting process equipment of 350psf

– Story weight distribution not finalized at time of lateral design

• Must be able to accommodate dramatic changes in layout with little structural rework

• Bracing confined to module perimeter

• Resilient in the event of moderate and major earthquakes

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The Opportunities

• State of the art design and design delivery

– Performance based design with strong backs and mechanical fuses

– Design process optimized for speed

– Design delivery based on high definition BIM

– Design optimized for construction speed and design flexibility

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Design Evolution

• 2016 “By the book” conventional BRB optimized for static design

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Evolution of Design

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G

A’

F’

2018


Design Evolution


• 2017 BRB, Trussed Strongbacks, and Krawinkler Fuses per code

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Evolution of Design

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G

A’

F’

2018


Design Evolution


• 2017 BRB, Trussed Strongbacks, and Krawinkler Fuses per code

• 2018 BRB, WF Strongbacks and Krawinkler Fuses – Performance Based Design per ASCE 7-10

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Evolution of Design

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G

A’

F’

2018


Structural Analysis

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MASTAN 2D Model

ETABS 3D Nonlinear Model

ETABS 3D Linear (“Code Check”) Model

SAP2000 2D Nonlinear Model

• Objectives of analysis• Understanding of structural behavior to guide design

decisions

• Demonstrate code compliance

• Four models working in parallel• Able to study numerous variants of lateral system in few

hours with MASTAN

• Three different analysis packages

• Three analysts

• Three models

• Reconciling differences in results between models led to greater understanding of behavior of the real worldstructure

Quality Assurance


Unknown Vertical Mass Distribution

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Braces sized to all be fully utilized at DBE for selected mass distribution

Higher mass at second floor

Expected floor mass distribution at time of design

Higher mass at third floor

Elimination of second floor

One Specific Case

What May (Likely) Happen


Robust Structural System

• Gravity and lateral systems decoupled for design and erection

• Members standardized based on worst-case loading scenario

• Strongbacks for dramatic changes in building configuration with no rework

• Yielding confined to Buckling Restrained Braces and Krawinkler Fuses

• All other members remain elastic.

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Strongbacks with BRBs

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Unconventional use of Conventional Buckling Restrained Braces

• Backbone properties based on brace manufacturer data

• Kinematic hysteretic hardening

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-5 -4 -3 -2 -1 0 1 2 3 4 5-1500

-1000

-500

0

500

1000

1500

Axial Deformation (inches)

Axia

l F

orc

e (

kip

s)

22 in2 core, 305 inches long


Fused Strongbacks (Krawinkler Fuses)

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17Krawinkler Fuses (Yielding Devices)

Backbone CurveMultilinear plastic element with kinematic hardening


Static Pushover Analysis

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Brace Force versus Roof Drift

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• Yielding of all BRBs occurs at drift demand (strongbacks)

• Max. brace for reached between 2%-2.5% roof drift.


Krawinkler Fuse Force versus Roof Drift

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• Fuses sized to yield early to provide damping at low level (service-level) events


Comparison with Conventional BRBF

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BRBs+Strongbacks+KFs

Conventional BRBF


Case of moving 66% of Floor 3 seismic mass to Floor 2

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• Mean maximum roof drift ratios less than 1.2% in strongback model with reasonably linear first-mode drift profile

• Undesirable concentration of demand at first story in conventional BRB design

0 0.01 0.02Story 1

Story 2

Story 3

Interstory Drift Ratio (rad.)

1979 ImpVal,CPE,xy

1979 ImpVal,CPE,yx

1981 Corinth,xy

1981 Corinth,Cor,yx

1987 NZ,Matahina,xy

1987 NZ,Matahina,yx

1992 Landers,DesHotSpr,xy

1992 Landers,DesHotSpr,yx

1992 Landers,Morongo,xy


1999 Duzce,Lamont,xy

1999 Duzce,Lamont,yx

2010 Darfield,SPFS,xy

2010 Darfield,SPFS,yx

Mean Max. Drift Ratio

0 0.005 0.01 0.015 0.02 0.025Base

Floor 1

Floor 2

Roof


1979 ImpVal,CPE,xy

1979 ImpVal,CPE,yx

1981 Corinth,xy

1981 Corinth,Cor,yx

1987 NZ,Matahina,xy

1987 NZ,Matahina,yx










0 0.005 0.01 0.015 0.02 0.025Base

Floor 1

Floor 2

Roof


1979 ImpVal,CPE,xy

1979 ImpVal,CPE,yx

1981 Corinth,xy

1981 Corinth,Cor,yx

1987 NZ,Matahina,xy

1987 NZ,Matahina,yx










BRB+Strongbacks+KF Conventional BRB


Weaker structures are better…

IF

Sufficiently ductile and damped

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Weaker structures are better…

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Benefit of Non-Linear Fuse Behavior – Base Shear

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Benefit of Non-Linear Fuse Behavior – Roof Drift

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Selected Design versus Code-Level Moment Frame Design

Roof Drifts and Roof Absolute Accelerations

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0 5 10 15 20 25 30 35 40 45 50-20

-15

-10

-5

0

5

10

15

20

Time (sec.)

Ro

of D

rift (

in.)

Moment Frame

Strongback+BRBs+KFs

Max. 16.8”

Max. 8.5”

0 5 10 15 20 25 30 35 40 45 50-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

Time (sec.)

Ro

of A

bs. A

cce

lera

tio

n (

g)

Moment Frame

Strongback+BRBs+KFs

Max. 0.6g

Max. 0.36g


In pursuit of more economical strongbacks…Performance Based Design

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23.5’

17.5’14’16’

Line 39 & 50

Line M

Line X

Building A’: Perimeter Frame Elevations


30Fused (Tall) Strongbacks

Fused (tall) strongback modeled with fuse links between W36x302 chords and W14 gravity column representing continuous line of fuses up height of strongback.

Fused (Short) Strongbacks

Fused strongback modeled with fuse links between W36x302 chords and W14 gravity column


Acceptance Criteria for NLRHAComponent Action Limit (DBE) Source

Drift ratio -- Mean drift ratios less than1.5%

ASCE 7-10 Table 12.12-1 “All otherstructures” for RC III

BRBs Deformation controlled

Mean axial strains less than 0.98%, which corresponds to plastic deformation ratio of 6.5

Plastic deformation ratio of 6.5 per Table 9-8 in ASCE 41-17, which corresponds to Damage Control (Level S-2) performance level. Per Sec. 2.3.1.2.1 halfway between IO (3*dy) and LS (10*dy) is 6.5*dy. Yieldstrain is ey=38/29000=0.13% so strain limit is 0.13%+6.5*0.13%=0.98%.

Fuses (in both tall and short strongbacks)

Deformation controlled

Mean shear deformations less than 2”

Per experimental testing blade bucklingand pinching in hysteretic curve starts at 2”

Strongback chords Forcecontrolled

Max. P-M DCRs in any ground motion <= 1.0

P-M DCRs calculated per AISC 360-10 Sec. H1

Pins at base of strongbacks Force controlled

Max. shear DCRs in any ground motion <= 1.0

Pin capacity in double shear

Collectors Force controlled

Max. axial DCRs in any ground motion <= 1.0

Axial DCRs calculated per AISC 341-10 and AISC 360-10

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Interstory Drifts, DBE intensity

• Mean drift ratios are less than 1.0% for A’

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Building F’Building A’


Demands in Fused Tall Strongbacks, Bldg A’

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Line 39

• Max. P-M demand (0.71 DCR) occurs in strongback chord just below Level 3F on Line 39

• Fused tall strongbacks are essentially elastic under upper bound DBE shaking

Results shown are for maximum combination of P,M for all ground motions, and are conservative since these would generally occur as different timesteps of the analysis.


Demands in Fused Short Strongbacks, Bldg A’

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• Max. P-M demand (0.85 DCR) occurs at top of the strongback chord on Line M

• Fused short strongbacks are essentially elastic under upper bound DBE shaking

Results shown are for maximum combination of P,M for all ground motions, and are conservative since these would generally occur as different timesteps of the analysis.

Line M


High Def BIM

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Key Structural Engineering Objectives & Pre-requisites

1. Get steel into the fabrication shops

a) Complete steel design, complete 3D modeling of gravity system, and extract mill order from model

2. Supply fabrication shops with shop drawings

a) Extract shop drawings from design model

3. Submit drawings and calculations for permit

a) Complete building design, including foundations, assemble comprehensive calculation package including documentation of global analysis for gravity and seismic forces and design calculations for each element of the building


Keys to Success

• Use design strategy with interleaved activities to complement construction schedule

• Focus on design critical path – order steel ASAP, complete design & shop drawings by time steel arrives plant, use bolted field connections, develop prefab exterior wall to weather proof fast

‾ Develop robust lateral system to accommodate changes

‾ Develop simple but robust gravity system that can be extended and modified easily (lots of shear studs)

‾ Uncouple lateral and gravity for design and erection

• Use integrated design, detailing, and fabrication team using same cloud-based Tekla model with detailers under the control of the structural engineer (change management)


Design Timeline for Modules D’, E’

Day Description

1 Receive go-ahead from Tesla to start conceptual design of Modules D’, E’

7 Issue mill order for Modules D’, E’ steel

20 Issue “structure only” permit drawing set for D’, E’ with comprehensive design calculationpackage

27 Issue Module D’, E’ foundation rebar shop drawings

35 Issue first steel shop drawings for Module D’

38 Start steel fabrication for Module D’

84 Issue last shop drawings for Module D’

85 Start steel erection for Module D’

124 Start steel erection for Module E’

137 Complete steel erection for Module D’

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Structural Engineering Strategies to Support Schedule

1. Concurrent editing of SAME cloud-based model by team

2. Issue construction drawings prior to permit drawings and calcs

3. Three structural teams providing HD BIM design

• Design/modeling team (GPLA) – concept & mill order

• Analysis team (Exponent Failure Analysis) – permit calcs

• Detailing team (DGI & BDS Vircon) – shop drawings

4. Uncouple gravity and lateral systems for design – issue gravity (80% of steel) ahead of seismic system steel

5. Provide high performance gravity system with double bay at 3rd floor and robust slab for 350 psf and fork lift traffic

6. Provide performance-based seismic design for superior performance, economy, and repairable damage in maximum EQ field bolted for minimum erection time

7. Panelize wall system design and integrate MEP supports


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Seismic Frames BRB-SB-KF on Exterior of Building F


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Rocking Fused Strongback Frame Field Bolted Frame

Rocking Strongback Frame

Krawinkler Fuse


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Details For Uncoupling Design with Robust Connections


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Level of Detail in Design Model & Gravity Enabling Details


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Federated Tekla Model - All

MEP Pipe Hangers Spot Cooler Support Structure

Federated Tekla model – MEP & S


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Modular Catwalk


September 15, 2016 Building D’ Steel Complete


Gigafactory Top Out November 7, 20165 Buildings

3.5 million Square Feet32,000 tons of structural steel

9500 tons of rebarAll steel and rebar shop drawings from GPLA HD BIM model

7 months from first phone call


Albert Einstein,

German born American Physicist

1879-1955

”Insanity is doing the same thing over and over again and expecting different results”

Corollary 1: If you want the same results, do the same thing.

Corollary 2: If you want something better, do something different.

Corollary 3: Find out the best its been done before you invent a better way – improve on the best.


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Thank you!

innovative building lateral system with strongback frames and … · 2018-10-01 · •2018 brb, wf...

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