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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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Design Evolution
• 2016 “By the book” conventional BRB optimized for static design
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Evolution of Design
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G
A’
F’
2018
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Design Evolution
• 2016 “By the book” conventional BRB optimized for static design
• 2017 BRB, Trussed Strongbacks, and Krawinkler Fuses per code
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Evolution of Design
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G
A’
F’
2018
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Design Evolution
• 2016 “By the book” conventional BRB optimized for static design
• 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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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Evolution of Design
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G
A’
F’
2018
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Strongbacks with BRBs
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Fused Strongbacks (Krawinkler Fuses)
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
17Krawinkler Fuses (Yielding Devices)
Backbone CurveMultilinear plastic element with kinematic hardening
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Static Pushover Analysis
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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.
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Krawinkler Fuse Force versus Roof Drift
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• Fuses sized to yield early to provide damping at low level (service-level) events
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Comparison with Conventional BRBF
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BRBs+Strongbacks+KFs
Conventional BRBF
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
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
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
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
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
1992 Landers,Morongo,xy
1999 Duzce,Lamont,xy
1999 Duzce,Lamont,yx
2010 Darfield,SPFS,xy
2010 Darfield,SPFS,yx
Mean Max. Drift Ratio
BRB+Strongbacks+KF Conventional BRB
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Weaker structures are better…
IF
Sufficiently ductile and damped
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Weaker structures are better…
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Benefit of Non-Linear Fuse Behavior – Base Shear
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Benefit of Non-Linear Fuse Behavior – Roof Drift
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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
In pursuit of more economical strongbacks…Performance Based Design
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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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23.5’
17.5’14’16’
Line 39 & 50
Line M
Line X
Building A’: Perimeter Frame Elevations
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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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GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
Interstory Drifts, DBE intensity
• Mean drift ratios are less than 1.0% for A’
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Building F’Building A’
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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.
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
High Def BIM
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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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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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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)
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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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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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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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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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Seismic Frames BRB-SB-KF on Exterior of Building F
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
42
Rocking Fused Strongback Frame Field Bolted Frame
Rocking Strongback Frame
Krawinkler Fuse
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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Details For Uncoupling Design with Robust Connections
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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Level of Detail in Design Model & Gravity Enabling Details
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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Federated Tekla Model - All
MEP Pipe Hangers Spot Cooler Support Structure
Federated Tekla model – MEP & S
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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Modular Catwalk
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
September 15, 2016 Building D’ Steel Complete
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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
GPLA & Exponent August 7, 2018 Innovative Building Lateral System w/ Strongbacks & Fuses© 2017 Gregory P Luth & Associates, Inc All rights reserved
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.