Innovative Building Lateral System with Strongback Frames and Mechanical Fuses

Transcription

1 1 Innovative Building Lateral System with Strongback Frames and Mechanical Fuses Gregory P. Luth, Ph.D., SE, SECB, GPLA John Osteraas, Ph.D., PE, Exponent SEAONC, August 7, 2018, San Francisco

2 2 The Gigafactory 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 G F Under construction A

3 3 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

4 4 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

5 5 Design Evolution 2016 By the book conventional BRB optimized for static design

6 6 Evolution of Design A G F 2018

7 7 Design Evolution 2016 By the book conventional BRB optimized for static design 2017 BRB, Trussed Strongbacks, and Krawinkler Fuses per code

8 8 Evolution of Design A G F 2018

9 9 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

10 10 Evolution of Design A G F 2018

11 Structural Analysis 11 Quality Assurance 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 world structure MASTAN 2D Model SAP2000 2D Nonlinear Model ETABS 3D Linear ( Code Check ) Model ETABS 3D Nonlinear Model

12 What May (Likely) Happen 12 Unknown Vertical Mass Distribution Higher mass at second floor One Specific Case Higher mass at third floor Expected floor mass distribution at time of design Braces sized to all be fully utilized at DBE for selected mass distribution Elimination of second floor

13 13 Robust Structural System Gravity and lateral systems decoupled for design and erection Members standardized based on worstcase 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.

14 14 Strongbacks with BRBs

15 Axial Force (kips) 15 Unconventional use of Conventional Buckling Restrained Braces Backbone properties based on brace manufacturer data Kinematic hysteretic hardening in 2 core, 305 inches long Axial Deformation (inches)

16 16 Fused Strongbacks (Krawinkler Fuses)

17 Krawinkler Fuses (Yielding Devices) 17 Backbone Curve Multilinear plastic element with kinematic hardening

18 Static Pushover Analysis 18

19 19 Brace Force versus Roof Drift Yielding of all BRBs occurs at drift demand (strongbacks) Max. brace for reached between 2%-2.5% roof drift.

20 20 Krawinkler Fuse Force versus Roof Drift Fuses sized to yield early to provide damping at low level (service-level) events

21 21 Comparison with Conventional BRBF Conventional BRBF BRBs+Strongbacks+KFs

22 22 Case of moving 66% of Floor 3 seismic mass to Floor 2 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 Roof Floor 2 Floor 1 Base Interstory Drift Ratio (rad.) BRB+Strongbacks+KF Roof Story ImpVal,CPE,xy 1979 ImpVal,CPE,yx 1981 Corinth,xy 1981 Corinth,Cor,yx Floor NZ,Matahina,xy 1987 NZ,Matahina,yx 1992 Landers,DesHotSpr,xy Story Landers,DesHotSpr,yx Floor Landers,Morongo,xy 1992 Landers,Morongo,xy 1999 Duzce,Lamont,xy 1999 Duzce,Lamont,yx Story Base 2010 Darfield,SPFS,xy Interstory Drift Ratio (rad.) Darfield,SPFS,yx Interstory Drift Ratio (rad.) Mean Max. Drift Ratio Conventional BRB 1979 ImpVal,CPE,xy 1979 ImpVal,CPE,xy 1979 ImpVal,CPE,yx 1979 ImpVal,CPE,yx 1981 Corinth,xy 1981 Corinth,xy 1981 Corinth,Cor,yx 1981 Corinth,Cor,yx 1987 NZ,Matahina,xy 1987 NZ,Matahina,xy 1987 NZ,Matahina,yx 1987 NZ,Matahina,yx 1992 Landers,DesHotSpr,xy 1992 Landers,DesHotSpr,x 1992 Landers,DesHotSpr,yx 1992 Landers,DesHotSpr,y 1992 Landers,Morongo,xy 1992 Landers,Morongo,xy 1992 Landers,Morongo,xy 1992 Landers,Morongo,xy 1999 Duzce,Lamont,xy 1999 Duzce,Lamont,xy 1999 Duzce,Lamont,yx 1999 Duzce,Lamont,yx 2010 Darfield,SPFS,xy 2010 Darfield,SPFS,xy 2010 Darfield,SPFS,yx 2010 Darfield,SPFS,yx Mean Max. Drift Mean Ratio Max. Drift Ratio

23 23 Weaker structures are better IF Sufficiently ductile and damped

24 24 Weaker structures are better

25 25 Benefit of Non-Linear Fuse Behavior Base Shear

26 26 Benefit of Non-Linear Fuse Behavior Roof Drift

27 Roof Drift (in.) Roof Abs. Acceleration (g) Selected Design versus Code-Level Moment Frame Design Roof Drifts and Roof Absolute Accelerations Moment Frame Strongback+BRBs+KFs Max. 0.6g Moment Frame Strongback+BRBs+KFs Max. 0.36g Max Max Time (sec.) Time (sec.)

28 28 In pursuit of more economical strongbacks Performance Based Design

29 Building A : Perimeter Frame Elevations Line 39 & 50 Line M Line X

30 Fused (Short) Strongbacks Fused strongback modeled with fuse links between W36x302 chords and W14 gravity column Fused (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. 30

31 Acceptance Criteria for NLRHA Component Action Limit (DBE) Source 31 Drift ratio -- Mean drift ratios less than 1.5% BRBs Fuses (in both tall and short strongbacks) Strongback chords Pins at base of strongbacks Collectors Deformation controlled Deformation controlled Force controlled Force controlled Force controlled Mean axial strains less than 0.98%, which corresponds to plastic deformation ratio of 6.5 Mean shear deformations less than 2 Max. P-M DCRs in any ground motion <= 1.0 Max. shear DCRs in any ground motion <= 1.0 Max. axial DCRs in any ground motion <= 1.0 ASCE 7-10 Table All other structures for RC III 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 halfway between IO (3*dy) and LS (10*dy) is 6.5*dy. Yield strain is ey=38/29000=0.13% so strain limit is 0.13%+6.5*0.13%=0.98%. Per experimental testing blade buckling and pinching in hysteretic curve starts at 2 P-M DCRs calculated per AISC Sec. H1 Pin capacity in double shear Axial DCRs calculated per AISC and AISC

32 32 Interstory Drifts, DBE intensity Mean drift ratios are less than 1.0% for A Building A Building F

33 33 Demands in Fused Tall Strongbacks, Bldg A 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 Line 39 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.

34 34 Demands in Fused Short Strongbacks, Bldg A 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 Line M 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.

35 35 High Def BIM

36 36 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

37 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)

38 Design Timeline for Modules D, E 38 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 calculation package 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

39 39 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 3 rd 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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41 41 Seismic Frames BRB-SB-KF on Exterior of Building F

42 42 Krawinkler Fuse Rocking Fused Strongback Frame Field Bolted Frame Rocking Strongback Frame

43 43 Details For Uncoupling Design with Robust Connections

44 44 Level of Detail in Design Model & Gravity Enabling Details

45 45 Federated Tekla Model - All Federated Tekla model MEP & S MEP Pipe Hangers Spot Cooler Support Structure

46 46 Modular Catwalk

47 September 15, 2016 Building D Steel Complete

48 Gigafactory Top Out November 7, Buildings 3.5 million Square Feet 32,000 tons of structural steel 9500 tons of rebar All steel and rebar shop drawings from GPLA HD BIM model 7 months from first phone call

49 Insanity is doing the same thing over and over again and expecting different results Albert Einstein, German born American Physicist 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.

50 50 Thank you!