PSC Single Span

7/29/2019 PSC Single Span

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Advanced Application 9

Single Span Composite Precast

Beams & Deck Bridge

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CONTENTS

Summary 1Bridge Dimensions / 1Materials / 2Loads / 3

File Opening and Preferences Setting 3

Material and Section Propert ies 4Material Properties / 4

Time Dependent Material Properties / 6Section Properties / 9

Structural Modeling Using Nodes and Elements 12Precast Beams / 13Cross Beams / 14Change Element Dependent Material Property / 15

Structure Support Conditions 16

Loading Data 18Load Groups / 18Static Loads / 18Prestress Loads / 22Moving Loads / 30

Construct ion Stage Data 38Groups / 38Define Construction Stages / 39

Performing Structural Analysis 45

Verification and Interpretation of Results 46Load Combinations / 46

Tendon Time-dependent Loss Graphs / 50Pretension Losses in Tendons / 51

Tendon Elongation / 52Influence Line / 53Moving Load Tracer / 54Stresses in Precast Beams during Construction Stages / 55Bending Moment Diagrams in Precast Beams / 57Shear Force Diagrams in Precast Beams / 59Reactions / 60


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SINGLE SPAN COMPOSITE PRECAST BEAMS AND DECK SLAB BRIDGE

1

Summary

This example shows the analysis of a 120-ft single span AASHTO bulb-tee beam bridgewith no skew, according to the AASHTO LRFD specifications. The structure consists ofsix precast, pretensioned beams spaced at 9-0 centers. Beams are designed to actcompositely with the 8-in. cast-in-place concrete deck to resist all superimposed deadloads, live loads and impact. A in. wearing surface is considered to be an integral partof the 8-in. deck. A 2 in. wearing surface will be installed in the future.

This example is similar to the one presented in the PCI Bridge Design Manual.

Bridge Dimensions:

Figure 1a Bridge Cross-Section

Figure 1b Precast Beam Dimensions


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Materials:

Concrete Deck and Cross BeamsASTM C4000Modulus of elasticity: 3834 ksiPoissons ratio: 0.2Density: 0.150 kcfConcrete strength (28-day) 4.0 ksiDeck total thickness 8.0 inDeck structural thickness 7.5 inCross beam depth 7.5 in (same as thickness of deck)Interior cross beam width 10 ft (c/c distance between adjacent cross-beams)End cross beam width 5 ft

Concrete Precast BeamsASTM C6500Modulus of elasticity: 4888 ksiPoissons ratio: 0.2Density: 0.150 kcfConcrete strength (28-day) 6.5 ksi

Steel Prestress Tendons: in. dia., seven-wire, low-relaxationModulus of elasticity: 28500 ksiUltimate strength: 270.0 ksi

Yield strength: 243.0 ksi

Loads:

Dead LoadConcrete deck

Exterior PC Beam (8/12ft) (7.5ft) (0.150kcf) =0.750 kip/ftInterior PC Beam (8/12ft) (9.0ft) (0.150kcf) =0.900 kip/ftHaunch above beam (0.5/12ft) (3.5ft) (0.150kcf) =0.022 kip/ft

Barrier(2 barriers)(0.300 kip/ft)/(6 beams) =0.100 kip/ft

Future wearing surface(2/12ft)(0.15kcf)(48ft)/(6 beams) =0.200 kip/ft

Prestress LoadStress in tendon before transfer =202.50 ksi (75% of ultimate strength)Assumed initial loss due to elastic shortening =9.2 % (18.6 ksi)Therefore: Stress in tendon after transfer =183.90 ksi

Moving Loads (AASHTO LRFD)HL-93


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3

File Opening and Preferences Setting

File / New ProjectFile / Save(PSC Single Span)

Tools / Unit SystemLength>in; Force (Mass)>kips

Figure 2 File Opening and References Setting


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4

Material and Section Properties

In this section the materials and sections used to model the structure are defined.

Material Properties:

The following materials are defined:DeckPrecast BeamsTendonsCross Beams.

In theTree Menu: Geometry / Properties / Material

Propertiesdialog box>Material tab>ClickName>DeckType of Design>ConcreteStandard>NoneModulus of Elasticity>3834(calculated for Grade C4000 as per AASHTO formula)Poissons Ratio>0.2Weight Density>0Click

Note:Deck weight density is assigned a value of zero, because we want to treat deck

weight as beam load, as opposed to self weight calculated automatically by theprogram after Composite Section for Construction Stage is created (refer page 40).

Figure 3 Material Data Window


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Name>Precast BeamsType of Design>ConcreteStandard>NoneModulus of Elasticity>4888(calculated for Grade C6500 as per AASHTO formula)Poissons Ratio (0.2)Weight Density (8.681e-005) kips/in3(i.e., 0.150 kcf)Click

Name>TendonType of Design>User DefinedStandard>NoneModulus of Elasticity>28500Poissons Ratio (0.3)Weight Density (8.681e-005) kips/in3(i.e., 0.150 kcf)Click

Note:In this tutorial the density of tendons is considered to be the same as the density ofconcrete, since it will be easier to compare results with the example presented inthe PCI Bridge Design Manual. The example in the PCI Bridge Design Manualdoes not consider separate density for tendons.)

Name>Cross BeamsType of Design>ConcreteStandard>NoneModulus of Elasticity>3834(calculated for Grade C4000 as per AASHTO formula)Poissons Ratio (0.2)Weight Density (0)Click

Note:Weight density of cross beams has been assigned a value of zero because these arefictitious beams used only for generating moving loads (refer to page 32).

Click


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6

Time Dependent Material Properties:

In theTree Menu: Geometry / Properties / Time Dependent Material (Creep /Shrinkage)

Time Dependent Material (Creep / Shrinkage) dialog box >ClickName>CEB-FIPCode>CEB-FIPCompressive strength of concrete at the age of 28 days>6.5Relative Humidity of ambient environment (4099)>70Notational size of member>10(This is a provisional value that will be replaced laterafter calculation by the program).Type of cement>Normal or rapid hardening cement (N, R)Age of concrete at the beginning of shrinkage>3

Click

Click

Click

Click

Figure 4 Creep and Shrinkage Data


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Figure 5 Creep Coefficient

In theTree Menu: Geometry / Properties / Time Dependent Material (Comp.

Strength)

Time Dependent Material (Comp. Strength) dialog box >ClickName>C6500Type>CodeDevelopment of Strength>Code>CEB-FIPConcrete Compressive Strength at 28 Days>6.5Cement Type(s)>N, R: 0.25

Click

Click

Click


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Figure 6 Compressive Strength Data

In theTree Menu: Geometry / Properties / Time Dependent Material LinkTime Dependent Material Type>Creep/Shrinkage>CEB-FIPTime Dependent Material Type>Comp. Strength>C6500Select Material to Assign>Materials>2:Precast BeamsClick

ClickClick

Figure 7 Time Dependent Material Link Window


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Figure 8 Section Data Window

Egd/Esb>1.2749Dgd/Dsb>0Consider Shear Deformation>(on)

Click

Note:Egd/Esb represents the ratio of Modulus of Elasticity for both types of concrete girder and slab. Therefore, Egd/Esb = 4888/3834 = 1.2749.

Dgd/Dsb is the ratio of unit weight for both types of concrete girder and slab. Ithas been assigned a value of zero because we want to treat deck weight as beamloads as opposed to self weight calculated automatically by the program.

Propertiesdialog box >Section tab>ID 1 (Interior Precast Beams)

ClickClick ID 2 (Interior Precast Beams)

ClickName>Exterior Precast BeamsSlab>Bc>90(this is the only difference between the two sections).

Click


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Propertiesdialog box >Section tab>Click Click DB/User tabName>End Cross BeamsClick User

Select Solid Rectangle( )H>7.5B>60

Click

Propertiesdialog box >Section tab>Click Click DB/User tabName>Interior Cross BeamsClick User

Select Solid Rectangle( )H>7.5B>120

Click

Click

Note:The depth of the Cross Beams is taken as the thickness of deck slab and width of theCross Beams is taken as the center-to-center distance between the Cross Beams.


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12

Structural Modeling Using Nodes and Elements

Tools / Unit SystemLength>ft; Force (Mass)>kips

Click Top View

In theTree Menu: Geometry / Nodes / CreateCoordinates (x,y,z)>0,0,0Copy>Number of Times>5Copy>Distances (dx,dy,dz)>0,9,0Click

Click

Figure 9 Create Nodes Window


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Precast Beams:

Click Auto FittingClick Node Number

In theTree Menu: Geometry / Elements / ExtrudeSelect Window >Nodes 1 and 6

Extrude Type>Node Line ElementElement Attribute>Element Type>BeamMaterial>2: Precast BeamsSection>2: Exterior Precast BeamsGeneration Type>TranslateTranslation>dx,dy,dz>10, 0, 0

Number of Times>12Click

Figure 10 Extrude Elements Window


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Select Window >Nodes 2to5

Extrude Type>Node Line ElementElement Attribute>Element Type>BeamMaterial>2: Precast BeamsSection>1: Interior Precast BeamsGeneration Type>TranslateTranslation>dx,dy,dz>30, 0, 0Number of Times>4Click

Cross Beams:

Select Window >Nodes 1 and 29

Extrude Type>Node Line ElementElement Attribute>Element Type>BeamMaterial>4: Cross BeamsSection>3: End Cross BeamsGeneration Type>TranslateTranslation>dx,dy,dz>0, 9, 0Number of Times>5Click

Select Window >Nodes 7to27by2

Extrude Type>Node Line ElementElement Attribute>Element Type>BeamMaterial>4: Cross BeamsSection>4: Interior Cross BeamsGeneration Type>TranslateTranslation>dx,dy,dz>0, 9, 0Number of Times>5Click

Click

Toggle on the Element Number to check the model geometry and the numberingof nodes and elements, and then toggle it off.


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Change Element Dependent Material Property:

This function is related to the Notational Size of Members and should be applied once the

elements have been generated.

In the Tree Menu: Geometry / Properties / Change Element DependentMaterial Property

Click Select AllElement Dependent Material>Notational Size of MemberSelect Auto Calculate

Click

Click

Figure 11 Change Element Dependent Material Property Window


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Structure Support Conditions

In theTree Menu: Geometry / Boundaries / Supports

Select Window >Node 1

Options>AddSupport Type (Local Direction)>D-ALL

Click

Figure 12 Supports Window

Select Window >Node 29

Support Type (Local Direction)>Dy, Dz

Click

Select Window >Nodes 2to6Support Type (Local Direction)>Dx, Dz

Click

Select Window >Nodes 30, 75to78

Support Type (Local Direction)>Dz

Click

Click


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Figure 13 Model Boundary Conditions


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Loading Data

The following items are defined in this section:Load groupsStatic loadsPrestress loadsMoving loads

Load Groups:

To perform Construction Stage analyses it is required to define groups of elements,boundary conditions and loads. Load groups are defined here to facilitate the assignmentof loads to their respective groups.

In theTree Menu: ClickGrouptabRight-click Load GroupSelect NewName>PC & C/B

ClickName>Deck

ClickName>Barrier

ClickName>Wearing surface

ClickName>Prestress

Click

Click

Static Loads:

In theTree Menu: ClickMenu tabStatic Loads> Static Load CasesName>DeckType>Dead Load of Component and Attachments (DC)

ClickName>Wearing surfaceType>Dead Load of Wearing Surfaces and Utilities (DW)

ClickName>BarrierType>Dead Load of Wearing Surfaces and Utilities (DW)

ClickName>PC & C/BType>Dead Load of Component and Attachments (DC)

Click


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Name>PrestressType>Prestress (PS)

ClickName>CreepType>Creep (CR)

ClickName>ShrinkageType>Shrinkage (SH)

Click

Click

Figure 14 Static Load Cases Window

Click Iso ViewClick Select Identity-ElementsSelect Identitydialog box>Select Type>SectionClick 1: Interior Precast Beams

Click

Click

In theTree Menu: Static Loads> Element Beam LoadsLoad Case Name>DeckLoad Group Name>DeckDirection>Global ZProjection>NoValue>Relativew>-0.922(0.900 deck +0.022 haunch)

Click


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Figure 15 Element Beam Loads Window

The loading is displayed in theModel Viewwindow.

Click Select Identity-ElementsSelect Identitydialog box>Select Type>SectionClick 2: Exterior Precast Beams

Click

Click

Load Case Name>DeckLoad Group Name>Deckw>-0.772(0.750 deck +0.022 haunch)

Click

Click Select Identity-ElementsSelect Identitydialog box>Select Type>SectionClick 1: Interior Precast Beams

ClickClick 2: Exterior Precast Beams

Click

Click

Click


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Load Case Name>Wearing surfaceLoad Group Name>Wearing surfacew>-0.2Click

Click Select PreviousLoad Case Name>BarrierLoad Group Name>Barrierw>-0.1

Click

Click

In theTree Menu: Static Loads> Self WeightLoad Case Name>PC & C/BLoad Group Name>PC & C/BSelf Weight Factor>Z>-1

Click

Click

Figure 16 Self Weight Window


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Prestress Data and Loads:

Figure 17 Strand Pattern

Figure 18 Longitudinal Strand Profile

Figure 19 Profile Insertion Points

In theTree Menu: ClickGrouptab

Right-click Tendon GroupSelect NewName>TendonSuffix>1to12

Click

Click


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In theTree Menu: ClickMenu tabStatic Loads>Prestress Loads> Tendon PropertyTendon Propertydialog box>ClickTendon Name>THTendon Type>Internal (Pre-Tension)Material>3: TendonClick to the right ofTotal Tendon AreaTendon Areadialog box>Strand Diameter>12.7mm (0.5)Number of Strands>14

Click

Select Relaxation CoefficientRelaxation Coefficient>Magura>45Ultimate Strength>270Yield Strength>243

Click

Figure 20 Add/Modify Tendon Property Window


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Tendon Propertydialog box>ClickTendon Name>TSTendon Type>Internal (Pre-Tension)Material>3: TendonClick to the right ofTotal Tendon AreaTendon Areadialog box>Strand Diameter>12.7mm (0.5)Number of Strands>34

ClickSelect Relaxation CoefficientRelaxation Coefficient>Magura>45Ultimate Strength>270Yield Strength>243

Click

Toggle off Node Number

Toggle on Element NumberClick Top ViewClick Select Identity-ElementsSelect Identitydialog box>Select Type>SectionClick 1: Interior Precast BeamsClick 2: Exterior Precast Beams

Click

ClickClick Activate


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In theTree Menu: Static Loads>Prestress Loads> Tendon ProfileTendon Profiledialog box>Click

Tendon Name>TH1Group>Tendon1Tendon Property>THClick inAssigned ElementsSelect Window >Elements 1to23by2Input Type>3-DCurve Type>SplineProfile>Reference Axis>StraightEnter the following data in theProfilewindow:

Figure 21 TH Tendon Profile Data

Profile Insertion Point>-6, 0, -52.79x-Axis Direction>X

Click

Note:

An insertion point is used as a point of reference for the tendon profile in theGlobal Coordinate System (GCS). Only one profile is needed for a precast beam inspite of the number of elements (four in this example) that we are using to model it.

As it is shown in Figure 19, the insertion points of both exterior and interior girdersare located at the bottom of the lower flanges. However, the vertical (Z-axis)coordinate of these points are different. This is because the distances from theneutral axis to the bottom fiber are not the same due to the differences in theirrespective effective widths of concrete slab.

Tendon Profiledialog box>SelectTH1Distance>

0, 108, 0

ClickSelectTH1-Copy

ClickTendon Name>Change toTH2Group>Change toTendon2Click inAssigned ElementsClick Unselect AllSelect Window >Elements 25to69by4Profile Insertion Point>Change to -6, 108, -54.57

Click


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Figure 23 TS Tendon Profile Data

Profile Insertion Point>-6, 0, -52.79x-Axis Direction>X

Click

Tendon Profiledialog box>SelectTS1Distance>0, 108, 0

ClickSelectTS1-Copy

ClickTendon Name>Change toTS2Group>Change toTendon8Click inAssigned ElementsClick Unselect AllSelect Window >Elements 25to69by4Profile Insertion Point>Change to -6, 108, -54.57

Click


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Tendon Profiledialog box>SelectTS2

ClickSelectTS2-Copy

ClickTendon Name>Change toTS3Group>Change toTendon9Click inAssigned ElementsClick Unselect AllSelect Window >Elements 26to70by4

Click

Use the same method described above to generate profiles for tendons TS4 & TS5.

ChangeGrouptoTendon10andTendon11 for TS4 and TS5, respectively.

Tendon Profiledialog box>SelectTS5

ClickSelectTS5-Copy

ClickTendon Name>Change toTS6Group>Change toTendon12Click inAssigned ElementsClick Unselect AllSelect Window >Elements 2to24by2

Profile Insertion Point>Change to -6, 540, -52.79Click

Click

Visually verify that the tendon profiles have been entered correctly.Click Iso ViewIn theTree Menu: ClickWorkstabPrestressing Tendon> Tendon ProfileRight-click mouse and selectDisplayClick Initial View

In theTree Menu: ClickMenu tabStatic Loads>Prestress Loads> Tendon Prestress LoadsLoad Case Name>PrestressLoad Group Name>PrestressSelect Tendon for Loading>Tendon>Select all tendons(TH1~TH6, TS1~TS6)

ClickStress Value>Stress1st Jacking>BeginBegin>183.9End>0


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Click

Click

Figure 24 Tendon Prestress Loads Window

Moving Loads:

Click Initial ViewClick Top ViewClick Activate AllClick

Element Number

In theTree Menu: ClickGrouptabRight-click Structure GroupSelect NewName>Cross BeamSuffix>1to5

Click

Click


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Figure 25 Define Structure Group Window

Select Intersect >Elements 73to85Drag & Drop Cross Beam 1from theTree Menu toModelView.

Figure 26 Assignment of Cross Beam Groups

Select Intersect >Elements 86to98


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Drag & Drop Cross Beam 2from theTree Menu toModelView.

Repeat the steps to defineGroupsCross Beam 3, Cross Beam 4 & Cross Beam 5.

The assignment of elements to groups can be verified by double-clicking each oftheGroups in theTree Menu and displaying their elements in theModel View.

Note:To increase the accuracy of vehicular live load analysis, the number of CrossBeams may be increased. This can be done by providing large number of equallyspaced fictitious Cross Beams in the transverse direction, having weight density= 0. The depth and width of these Cross Beams will be equal to the deck slabthickness and center-to-center distance between the Cross Beams, respectively.

Tools / Unit SystemLength>ft; Force (Mass)>kipsToggle on Node Number

Toggle off Element Number

In theTree Menu: ClickMenu tabMoving Loads Analysis> Moving Load CodeSelect Moving Load Codedialog box>Moving Load Code>AASHTO LRFD

Figure 27 Traffic Lanes and their Eccentricities

Moving Loads Analysis> Traffic Line LanesTraffic Line Lanesdialog box>ClickLane Name>Lane 1Eccentricity>-4.5Vehicular Load Distribution>Cross BeamCross Beam Group>Cross Beam 1Moving Direction>BothSelection by>2 pointsClick in the first box belowSelect Window >Nodes 1 and 29


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Click

Click

Figure 28 Definition of Design Traffic Line Lanes

Traffic Line Lanesdialog box>ClickLane Name>Lane 2Eccentricity>-16.5Vehicular Load Distribution>Cross BeamCross Beam Group>Cross Beam 2Moving Direction>BothSelection by>2 pointsClick in the first box below


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Select Window >Nodes 1 and 29

Click

Click

Traffic Line Lanesdialog box>ClickLane Name>Lane 3Eccentricity>-28.5Vehicular Load Distribution>Cross BeamCross Beam Group>Cross Beam 4Moving Direction>BothSelection by>2 pointsClick in the first box belowSelect Window >Nodes 1 and 29

ClickClick

Traffic Line Lanesdialog box>ClickLane Name>Lane 4Eccentricity>-40.5Vehicular Load Distribution>Cross BeamCross Beam Group>Cross Beam 5Moving Direction>BothSelection by>2 pointsClick in the first box below

Select Window >Nodes 1 and 29Click

Click

Click


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In theTree Menu: Moving Load Analysis> VehiclesVehiclesdialog box>Click

Standard Name>AASHTO LRFD LoadVehicular Load Name>HL -93TDMVehicular Load Type>HL -93TDMDynamic Allowance: 33(%)

Click

Figure 29 Definition of Standard Vehicular Loads

Vehiclesdialog box>ClickStandard Name>AASHTO LRFD Load

Vehicular Load Name>HL-93TRKVehicular Load Type>HL-93TRKDynamic Allowance: 33(%)

Click

Click


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In theTree Menu: Moving Load Analysis> Moving Load Cases

Moving Load Casesdialog box>ClickLoad Case Name>MLCEnter the following data in theMultiple Presence Factor window:

Figure 30 Multiple Presence Factors

Sub-Load Cases>Loading Effect>Independent

ClickSub-Load Casedialog box>Vehicle Class>VL:HL-93TDM Scale Factor>1Min. Number of Loaded Lanes>1Max. Number of Loaded Lanes>4Assignment Lanes>List of Lanes>Select all lanes(Lane 1, Lane 2, Lane 3, Lane 4)

Click

Click

Define Moving Load Casedialog box>Click

Sub-Load Casedialog box>Vehicle Class>VL:HL-93TRKScale Factor>1Min. Number of Loaded Lanes>1Max. Number of Loaded Lanes>4Assignment Lanes>List of Lanes>Select all lanes(Lane 1, Lane 2, Lane 3, Lane 4)

Click

Click

Click


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Figure 31 Definition of Moving Load Cases


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Construction Stage Analysis Data

Three stages are defined to model the bridge during construction. Details of theconstruction stages are shown below:

Stage Day Description

Stage 1 (30 days) 1Placing of precast beams and cross beams.Prestressing of strands.

21 Pouring deck slab.

Stage 2 (30 days) 1 Composite beam & slab behavior takes place.

1 Installation of barrier.

6 Placing of wearing surface.

Stage 3 (10000 days) - -

Note: Age of all precast members (precast beams & cross beams) is 7 days at the time ofplacing (1st day of Stage 1).

Table 1.2 Construction Stages

Groups:

In theTree Menu: ClickGrouptabRight-click Structure GroupSelect NewName>All

Click

ClickClick Select AllDrag & Drop All from theTree Menu toModel View

Right-click Boundary GroupSelect New

Name>SupportsClick

ClickClick Select AllDrag & Drop Supports from theTree Menu toModel ViewSelect Boundary Typedialog box>Support

Click


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Define Construction Stages:

In theTree Menu: ClickMenu tabConstruction Stage Analysis Data> Define Construction Stage

Construction Stagedialog box>ClickStage>Name>StageStage>Suffix>1to3Save Result>Stage,Additional Steps(on)

Click

Construction Stagedialog box>ClickStage>Stage 1

Name>Stage 1Duration>30Additional Steps>Day>21

Click in theAdditional Stepswindow

Click Element tabGroup List>AllActivation>Age>7

Click in theActivationwindow

Click Boundarytab

Group List>SupportsSupport/Spring Position>Deformed


Click LoadtabGroup List>PC & C/B

Click in theActivationwindowGroup List>Prestress

Click in theActivationwindowGroup List>Deck

Active Day>21Click in theActivationwindow

Click

Construction Stagedialog box>ClickStage>Stage 2Name>Stage 2Duration>30Additional Steps>Day>6

Click in theAdditional Stepswindow


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Click LoadtabOnce activated, the Element, Boundary and Load groups remain active unless they

are specifically deactivated.Group List>Barrier

Click in theActivationwindowGroup List>Wearing SurfaceActive Day>6


Click

Figure 32 Definition of Construction Stage 1


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Figure 33 Definition of Construction Stage 2

Construction Stagedialog box>ClickStage>Stage 3Name>Stage 3Duration>10000

Click

Click


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In theTree Menu: Construction Stage Analysis Data > Composite Section forConstruction Stage

Composite Section for Construction Stagedialog box>ClickActive Stage>Stage 1Section>1: Interior Precast BeamsComposite Type>Normal

Construction Sequence>Part>1:Material Type>MaterialMaterial>2:PrecastComposite Stage>Active StageAge>7

Construction Sequence>Part>2:Material Type>MaterialMaterial>1:DeckComposite Stage>Stage 2Age>10

Click

Figure 34 Composite Section 1 (Interior Precast Beams) during Construction Stages


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Composite Section for Construction Stagedialog box>ClickActive Stage>Stage 1Section>2: Exterior Precast BeamsComposite Type>Normal

Construction Sequence>Part>1:Material Type>MaterialMaterial>2:PrecastComposite Stage>Active StageAge>7

Construction Sequence>Part>2:Material Type>MaterialMaterial>1:DeckComposite Stage>Stage 2Age>10

Click

Click

Figure 35 Composite Section 2 (Exterior Precast Beams) during Construction Stages


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In theMain Menu:Analysis/ Construction Stage Analysis ControlFinal Stage>Last StageAnalysis Option>Include Time Dependent Effect (on)Time Dependent Effect>Creep & Shrinkage(on)Type>Creep & ShrinkageAuto Time Step Generation for Large Time Gap (on)Tendon Tension Loss Effect (Creep & Shrinkage) (on)Variation of Comp. Strength (on)Tendon Tension Loss (Elastic Shortening) (on)Frame Output>Calculate Output of Each part of Composite Section (on)

Load Cases to be Distinguished from Dead Load for CS Output:Load Case>Wearing Surface

ClickLoad Case>Barrier

Click

Click

Beam Section Property Changes>Change with TendonSave Output of Current Stage (Beam/Truss) (on)

Figure 36 Construction Stage Analysis Control Data


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Perform Structural Analysis

In theMain Menu:Analysis/ Perform Analysis


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Verification and Interpretation of Results

Load Combinations:

Select the Post Construction Stage ( ).In theTree Menu: ClickMenu tab.Results> Combinations

Load Combinationsdialog box>General tab>ClickOption>AddAdd Envelope(on)Code Selection>ConcreteDesign Code>AASHTO-LRFD02

Manipulation of Construction Stage Load Case>CS Only

Note:Do not select ST+CS option (Static Load + Construction Stage) since the outputwill be misleading. Bridge Deck and PC & C/B have been defined as bothDead Load of Components and Attachments (DC) as well as Construction Stage(CS) Loads. Similarly, Wearing Surface and Barrier have been defined as bothDead Load of Wearing Surface and Utilities (DW) as well as Erection Loads(EL). (Refer to Loading Data and Figure 36 for details). Thus, these dead loadswill appear twice in the output if the ST+CS option is selected.

Load Modifier>1Load Factors for Permanent Loads (Yp):Component and Attachments>Load Factor>BothWearing Surfaces and Utilities>Load Factor>Both

Condition for Temperature, Creep, Shrinkage Factor>Deformation Check

Click


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Figure 37 Generation of Load Combinations


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Figure 38 Auto Generated Load Combinations

.

Figure 39 Definition of the Envelope


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Click

Change the load factors for the load combinations gLCB15, gLCB16 and gLCB17(Service I, II and III, respectively) as shown in Table 1.3.

This step is required to generate appropriate deformations as per AASHTO-LRFD02.

The factors for loads not listed in Table 1.3 are zero and their cells can be left blank.

Click

LoadComb.

MLCDeadLoad

ErectionLoad

TendonPrimary

TendonSecondary

CreepPrimary

CreepSecondary

ShrinkagePrimary

ShrinkageSecondary

gLCB1 1.75 1.25 1.50 1.00 1.20 1.20

gLCB2 1.75 1.25 0.65 1.00 1.20 1.20

gLCB3 1.75 0.90 1.50 1.00 1.20 1.20

gLCB4 1.75 0.90 0.65 1.00 1.20 1.20

gLCB5 1.35 1.25 1.50 1.00 1.20 1.20

gLCB6 1.35 1.25 0.65 1.00 1.20 1.20

gLCB7 1.35 0.90 1.50 1.00 1.20 1.20

gLCB8 1.35 0.90 0.65 1.00 1.20 1.20

gLCB9 1.25 1.50 1.00 1.20 1.20

gLCB10 1.25 0.65 1.00 1.20 1.20

gLCB11 0.90 1.50 1.00 1.20 1.20

gLCB12 0.90 0.65 1.00 1.20 1.20

gLCB13 1.50 1.50 1.00 1.20 1.20gLCB14 1.50 0.65 1.00 1.20 1.20

gLCB15 1.00 1.00 1.00 1.00 1.20 1.20

gLCB16 1.30 1.00 1.00 1.00 1.20 1.20

gLCB17 0.80 1.00 1.00 1.00 1.20 1.20

gLCB18 0.75

Table 1.3 Load Combinations for Construction Stages


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Tendon Time-dependent Loss Graph:

In this tutorial, the prefix TH stands for harped tendon and TS stands for straight tendon.

Animate button can be used to view the Loss Graphs for all the stages for the selectedtendon, sequentially.

In theTree Menu: Results> Tendon Time-dependent Loss GraphGraph for tendon TH1 in Stage 1 is automatically displayed.Tendon>TH2Stage>Stage 1Step>Last Step

Click

Figure 40 Tendon TH2 Loss GraphTendon>TS2

Figure 41 TS2 Tendon Loss Graph

Click


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Pretension Losses in Tendons:

In theTree Menu: ClickTablestab.

Result Tables >Tendon > Tendon LossClickTendon Group >Tendon 1, Tendon 2, Tendon 3, Tendon 4, Tendon 5,Tendon 6, Tendon 7, Tendon 8, Tendon 9, Tendon 10, Tendon 11, orTendon 12.Click Stage>Stage 1, Stage 2, or Stage 3.

Click

Since losses are calculated using CEB-FIP code, they are different from those givenin the PCI Bridge Design Manual, where losses are calculated using AASHTO code.

Figure 42 Pretension Losses (Stress) in Tendons

Figure 43 Pretension Losses (Force) in Tendons


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Tendon Elongation:


In theTree Menu: ClickTablestab.Result Tables>Tendon> Tendon Elongation

Figure 44 Tendon Elongation


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Influence Line:

Click Model Viewtab.

Click Initial ViewClick Iso ViewTools / Unit SystemLength>ft; Force (Mass)>kips

In theTree Menu: ClickMenu tab.Results >Influence Lines > Beam Forces/Moments

Line/Surface Lanes>LANE allKey Element>13Scale Factor>1Parts>jComponents>MyType of Display>Legend (on)

Click

The influence line diagram for moment (My) at the end of Element 13 is displayed.This position corresponds to the mid-span of one of the interior girders.

Figure 45 Influence Line Diagram


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Moving Load Tracer:

Click MVL Tracer tab.

Select Beam Forces/MomentsMoving Load Cases>MVmax: MLCKey Element>13Scale Factor>1Parts>jComponents>MyType of Display>Contour (on) ; Legend (on) ; Applied Loads(on)

Click

Click

The position of moving loads that generate maximum moment (My) at the end ofElement 13 is displayed. This position corresponds to the mid-span of one of theinterior girders.

Figure 46 Moving Load Tracer


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Stresses in Precast Beams during Construction Stages:

Select Stage 1 in theToolbar ( )Tools / Unit SystemLength>in; Force (Mass)>kips

In theTree Menu: ClickTabletab.

Result Tables>Composite Section for C.S.> Beam StressRecords Activationdialog box:Loadcase/Combination>Summation(CS)Stage/Step>Stage 1:0003(last) (on) ; Stage 2:0003(last) (on)Part Number>Part j

Click

Figure 47 Records Activation Dialog Window

The table showing axial, bending and combined stresses for the precast beams (elements1to72) at their j end in construction stages 1 and 2 is displayed.


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Figure 48 Stresses in Precast Beams during Construction Stages


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Bending Moment Diagrams in Precast Beams:

Tools / Unit SystemLength>ft; Force (Mass)>kipsClick Top View

Toggle on Element NumberSelect Window >Elements 25to69by4Click ActivateClick Front View

Click Model Viewtab.In theTree Menu: ClickMenu tabResults >Forces > Beam DiagramsLoad Cases/Combinations>CS: SummationComponents>MyDisplay Options>5 Points (on) ; Solid Fill (on)Type of Display>Contour (on) ; Legend (on)

Click

The bending moment diagram (My) for the selected interior precast beams (elements25to69by4) in the current construction stage (Stage 1), and under all the constructionstage loads applied simultaneously, is displayed.

Figure 49 Stage 1 Bending Moment Diagram of Precast Beams


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Toggle on Active Fix in theStatus Bar

SelectPost Construction Stage( ).Load Cases/Combinations>CBall: RC ENV_STRComponents>My

Click

The post-construction stage (Post CS) envelope of bending moment diagram (My)under strength condition for the selected interior precast beams (elements 25to69by4),is displayed.

Figure 50 Post-Construction Stage Bending Moment Diagram Envelope of Precast Beam


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Shear Force Diagrams in Precast Beams:

Load Cases/Combinations>CBall: RC ENV_STRComponents>Fz

Click

Click

The post-construction stage (Post CS) envelope of shear force diagram (Fz) understrength condition for the selected interior precast beams (elements 25to69by4), isdisplayed.

Figure 51 Post-Construction Stage Shear Force Diagram Envelope of Precast Beams


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Reactions:

In theTree Menu: ClickTablestab.Result Tables > ReactionRecords Activationdialog box>Loadcase Combination>gLCB1(CB:max)

Click

Figure 52 Records Activation Dialog Box

The table showing the maximum reactions corresponding to Load Combination LCB1in the post construction stage (Post CS) is displayed.

Figure53Post ConstructionMaximumReactionsduetoLoadCombinationLCB1

PSC Single Span

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