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Lecture 5Part 1

Construction MethodsEngineering for the Las Vegas

High Roller Ferris Wheel

Tom Zieman, P.E., S.E.

Principal

Zieman Engineering, LLC

BSCES SEI BOSTON – 2017 LECTURE SERIESConstruction Aspects of Structural Engineering – “If You Design

It, Can They Build It?”

Zieman Engineering, LLCStamford, CT

Project Participants

• Owner – Caesars Entertainment

• Permanent Structure Designer – Arup

• Contractor – American Bridge Company

• Construction Methods Engineer– American Bridge Company

– Zieman Engineering, LLC

Construction started 2012, open to public April 2014

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Structure Dimensions• 550’ tall• 460’ diameter wheel• 28 cabins

Major Components• Legs• Hub/Spindle• Wheel• Cabins

Construction Engineering Criteria

• Partially completed structure capable of withstanding loadsspecified in ASCE 37 “Design Loads on Structures DuringConstruction”– Goal – the same structural reliability as the permanent structure, but

based on the exposure duration of construction

• Wind speed of 80 MPH

• Seismic load assumed less than wind based on duration ofconstruction

• Permanent structure to have dead load force distribution andfinal geometry specified by the EOR within the tolerancesspecified by the EOR

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Construction phases

1. Legs

2. Hub/Spindle

3. Wheel

4. Cabins

Leg Construction

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Legs Dimensions

• Total Height 282’• Pipe 94”-110” Diameter• 1.38”-2.36” Wall Thickness• Fabricated Lengths 26’-75’• Erected Lengths 75’-109’• 3 Levels of Erection

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Hub/Spindle Construction

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Hub• 14’-9” Diameter• 1.57” Wall• 108’ Long

Spindle• 9’-10” O.D.• 1.18” Wall• 108’ Long

Spherical Bearing

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Wheel Construction

Wheel Configuration• Compression ring 79”

diameter pipe with 1” thickwall

• 460 feet diameter• 28 rim segments with internal

flanged connections• 112 cables – 3” diameter

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Rim 3062 k CompressionCable Tension 152 kips

Rim 3958 kips Compression

Cable Tension 199 kips

Cable Tension 254 kips

Wheel Final Force Configuration

Wheel Construction Objectives Specified by EOR

• Force objective – All cables at a load of 254 kips +/- 5% whenat the 6:00 position prior to installing cabins (maximum 267kips, minimum 241 kips)

• Geometry Objective– Wheel radius at 6:00 position must be the same value for any rotation

of the wheel +/- 1” (0.036% of the radius)

– Wheel transverse location at the 6:00 position must not vary fromtheoretical centerline by more than 1” for any rotation of the wheel.

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Camber Calculation

• Determine the fabrication dimensions (unstressed condition)which will result in the correct geometry in the final (stressed)condition

• The wheel has to be made 2” larger in diameter

• The cables have to be made about 3” shorter than their finallength

General Construction Procedure Development

• The rim does not function as acompression ring until complete.Therefore, radial struts would benecessary to hold the rim in place duringconstruction.

• No piece of equipment could reasonablyplace the rim segments at the top of thewheel. Therefore, all rim segmentswould be installed at the 6:00 positionand the wheel rotated duringconstruction.

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Construction Decision AffectingProcedure and Modeling – CableInstallation Method

• Install to calculated force• Requires extremely accurate

force measurements• Requires more complex

structural model that accuratelypredicts the forces in the realstructure

• Install to calculated geometry• Requires accurate as-built

information (includingtolerances) of all structuralcomponents

Solution:• Install cable to calculated

geometry, but also measureforce to compare to predictions

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Staged Construction Analysis Model Objective

• Determine the member forces at each stage of constructionto verify the permanent structure members are withincapacity

• Determine required design capacities for all temporarycomponents

• Verify the feasibility of the assumed construction sequenceand make refinements

• Determine anticipated forces during each stage for thepurpose of monitoring during construction

• Determine anticipated deflections during each stage for thepurpose of monitoring during construction.

SAP2000 Model

• 147 construction stages• All components in model, but

only those that are present in astage are turned on

• Gravity direction is rotated toaccount for different positionsof wheel

• All dead loads input asmembers with mass so that theload direction will correspondto gravity direction

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Model Detail at Rim

Model Detail at Hub

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TypicalStageOutput

TypicalStageOutput –Deflections

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Typical StageOutput -Moments

Temporary Support Structures

• Radial Struts

• Hydraulic Rotating Mechanism

• Holdback Tower

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Radial Struts

Radial Struts• 224 feet long each• 18 struts – 4032 feet total length• Interior segments 6’-9” x 6’-9” x 45’-0” long• Interior segments intended to be usable for future projects

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Hydraulic Rotating Mechanism

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Holdback Tower

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Holdback Tower

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As-Built Survey of Components Affecting RadialDimensions

• Survey of holes on hub

• Survey of end hardware on cables

• Survey of holes on rim sections

• Survey of ends of each rim section

All surveys were made in the shop using very accurate totalstation equipment (accuracy 0.1mm), then an as-builtrepresentation of the structure was created in 3D cad todetermine the adjusted cable setting dimensions.

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Rim Closing Plan

• Lower rim sections adjacent to final section by looseningcables so that the gap opens up

• Insert last rim section

• Pull rim back into shape by jacking cables

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Rim Closing Reality

• Gap 9” less than anticipated

• Reasons– 3” due to oversize of radial strut holes

– Remaining 6” unaccounted for – assumed fabrication tolerance orcumulative error of shop survey error

• Solution– Remove 3” of adjustment shims between last two segments

– Hang weights from segments adjacent to last segment to open the gapmore

– Check structural model for hanging weights and forcing in longsegment to verify no overload in rim, cables or radial struts

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Gap when segment near finalelevation

Gap when segment at final elevation

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Final Cable Installation Reality – Higher ForcesThan Anticipated

• As radial struts were removed and final cable were installedbased on geometry, measured cable force becameprogressively larger than anticipated – up to 30% larger.

• The forces required to unload the radial struts were also muchhigher than predicted by the model.

• Likely cause – geometric error. Possible reasons:– Rim fabricated larger than it was supposed to be

– Cables fabricated shorter than they were supposed to be

– Cumulative as-built survey error during progressive assembly of rim

– Dimensional calculation error

• Actual cause –unknown – but the solution for all possibilitiesis the same – change the cable setting geometry

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Solution to Achieve Correct Cable Forces

• Assume that from a modeling viewpoint, the problem can be representedas an imposed elongation of the rim circumference.

• Determine the imposed elongation that best fits the force measurementsalready done:– Retrieve data for cables already installed, and measure tension in additional

accessible cables – 21 data points total.– For each data point, run the SAP model stage corresponding to the point in

time the measurement was taken, and through trial and error determine theimposed elongation of the rim that will reproduce the measured force. Thisgave imposed elongation values between 3” and 10”

– Take a weighted average of the data points based on the assumed reliability ofthe force measurement. Result – rim is 6.6” bigger in circumference than it issupposed to be.

• Adjust the model for all future stages to reflect the increase in rim size.• Adjust the cable setting measurements for all future cables to reflect the

increase in rim size

Result of Geometric Cable Setting Corrections

• After making the correction to the cable setting lengths tocorrect for the larger rim, all future cables matched thepredicted forces generally within 5%. A few cables weremore than 5% off – at worst 10%.

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Final Wheel Construction Steps

• A cable tension survey was done at night when temperaturegradients in the structure were lowest. The tension in allcables was measured at the 6:00 position.

• A rim position survey was done simultaneously with thetension survey

• After the survey, approximately 10% of the cables wereoutside the 5% tension tolerance. The model was used todetermine how to adjust the tension in these cables so thatthey would have minimal effect on adjacent cables

• The cables outside the 10% tolerance were adjusted andtension remeasured

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Cabin Installation

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Project Conclusion

Highly Successful Project for All Parties

• The project was delivered to the owner on time and onbudget

• The contractor and the EOR worked together to solve anydesign issues

• The required force and geometric tolerances were met

• The quality of construction was high

• Through extensive planning, the contractor’s field labor costwas significantly less than anticipated

Questions?

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BSCES SEI BOSTON – 2017 LECTURE SERIESConstruction Aspects of Structural Engineering– “If You Design It, Can They Build It?”

Lecture 5Part 2

Assembly and FieldErection of Larger GirderAssemblies for the New

Tappan Zee Bridge

Tom ZiemanPrincipalZieman Engineering, LLCStamford, CT

Video or photography is not allowed during thispresentation. The information (electronic or hardcopy)contained in this presentation is intended for the exclusiveuse of this presentation and may contain information thatis confidential or sensitive. Dissemination, forwarding,printing, or copying is strictly prohibited. Informationregarding the New NY Bridge Project that can be circulatedis available on NewNYBridge.com Photos courtesy of NewYork State Thruway Authority.

To comply with the above restrictions only this trimmeddown portion of the presentation is allowed to bedistributed.

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Load-OutBarge

TrestleRunway

Girder Assembly AreaTower Crane

Land Runway

Barge Delivery Slip

Assembly Area

Assembly Line Stations

Girder/CrossframeAssembly

Catwalk/MiscellaneousInstallation

Electrical Installation

Connection Painting,Inspection, Load-Outto Barge

ConnectionPainting

ASSEMBLY LINE STATIONS

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Intermediate Grillages for Girder Assembly (Duringassembly +/- 100’ spacing)

Tower Crane

Assembly Support Grillages (After assembly 260’ spacing)

Girder Transporters

Land Runways

Trestle Runways

Winch System

Barge Grillage

Straddle crane Trestle

ASSEMBLY LINE COMPONENTS

• Structural Analysis of Girder Assemblies

• Design of Lifting Frame

• Photos of Field Erection

FIELD ERECTION OF GIRDER ASSEMBLIES

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Girder AssemblyLifting Frame• 175’ long x 42’ wide• Supported on crane

with 14” diameterwire rope slings

• Adjustable girderconnections toaccommodatedifferent types ofassemblies

• Hydraulicallyadjustable to slopeframe to matchassemblysuperelevation,longitudinal slope andcenter of gravitylocation

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