Pre Stress

7/30/2019 Pre Stress

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Beca Carter Hollings & Ferner Ltd A EXCEL WORKSHEETJOB NAME: Sarawak Coastal Road JOB NO: 9101179SUBJECT: 30m girder PAGE NO: O

BY: WEP DATE: 5/15/2013

Methodology

The aim of this spreadsheet is to assess the stresses in a simply supported

prestressed girder for serviceability stresses. The designer must consider the following effects

when determining the boundary parameters of the girder

a) reduce the strand eccentricity at the end of the girder to limit end girder rotations

b) aim for load balancing at midspan for long term loads

c) the spacing between strands and cover must satisfy the appropriate specifications

This spreadsheet consists of 7 worksheets plus this summary

They are: Sheet No

A

B

C

D (not required for DHC unit)E

F (not usually relevant)

The user is required to enter data into cells denoted

The analysis calculates stresses in a girder from one end to the girder center

and allows for debonding of some strands (inputted as a strand layer)

More than one strand layer may occur at the same level

The stresses calculated at transfer are base on the girder section properties. The short term elastic

loss value is calculated in sheet B. This loss is subtracted from the strand forces

This force is required for the creep and shrinkage calculations

The stresses calculated at final DL+long term losses (sheet C) are based on girder section properties.

The additional stresses from SDL are derived using the composite girder section property

The aim for this sheet is to determine if the girder is load balanced between long term loads (DL+SDL)

and prestressing flexural stresses.

This sheet also determines the maximum average final stressing force after all losses

have been included. This tells the designer if more stressing at transfer is permitted.

Summary - Final Losses + DL

Worksheet Name Requires Input

YesInput

Yes

Yes

Summary at Transfer

Equivalent Load

Yes

No

NoMonolithic SummarySummary - Final Load Effects


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Beca Carter Hollings & Ferner Ltd A EXCEL WORKSHEET

SUBJECT: 30m girder PAGE NO: A

BY: WEP DATE: 5/15/2013

Input Data for Post Tensioned / Prestressed Girder

Prestressed Girder Assessment

Girder Length L= 29.9 m

TENDON PROPERTIES

Strand Type 12.7 mm strand

Strand UTS 184 kN

Strand Area 100 mm2

EP 195000 MPa (Modulus of Elasticity)

Tendon Profiles H1 Unbonded Length (x)

No of

Strands Aps UTS Load

Tendon 1 0.065 0 12 1200 2208

Tendon 2 0.115 5 12 1200 2208

Tendon 3 0.165 0 12 1200 2208

Tendon 4 0.215 0 12 1200 2208

Tendon 5 1.135 0 2 200 368Tendon 6 0 0

Total No of Strands 50

Tendon Force Input

Average Force at Stressing per strand fps 140 kN 76%

Area of Stressing Aps 5000 mm2

L

H1

Unbonded length x


3/7

Beca Carter Hollings & Ferner Ltd AJOB NAME: Sarawak Coastal Road

SUBJECT: 30m girder

BY: WEP

Summary of Transfer StressesTotal No of Strands 50Transfer force (average) for one strand 140 kN or 0.76 UTSMaximum force (average) for one strand after lock off 135 kN or 0.74 UTS

Short Term Elastic LossConcrete Property Sections for Girder section only cl 9-9.2.2.5*** ES = (Es/Eci).fcir

Girder depth d = 1.2 mArea (girder) = 0.4798 m2 fcir = concrete stress at tendon locationIxx (girder) = 0.08733 m4 due to prestressing force at transfer and

Dist to N/A from so f f i t of gi rder y= 0.556 m of member at max momentZtop (girder) = 0.135606 m3Zbot (girder) = 0.157068 m3 fcir = 5.92 MPa

Short Term Elastic Loss ES = 46.2 MPaEquivalent Force = 4.62 kN (per

Determine Average Eccentricity from Soffet and total post tensioning force at each location *** Reference - Onterio Hi hwa Brid e DDistance 0 1.50 2.99 4.49 5.98 7.48 8.9

Force Tendon 1 1625 1625 1625 1625 1625 1625 16

Distance from Soffit Tendon 1 0.07 0.07 0.07 0.07 0.07 0.07 0.Force Tendon 2 0 0 0 0 1625 1625 16

Distance from Soffit Tendon 2 0.00 0.00 0.00 0.00 0.12 0.12 0.

Force Tendon 3 1625 1625 1625 1625 1625 1625 16


Force Tendon 4 1625 1625 1625 1625 1625 1625 16


Force Tendon 5 271 271 271 271 271 271 27

Distance from Soffit Tendon 5 1 14 1 14 1 14 1 14 1 14 1 14 1


4/7

Beca Carter Hollings & Ferner Ltd AJOB NAME: Sarawak Coastal RoadSUBJECT: 30m girder

BY: WEP

Summary of Final Stresses plus Dead Load & SDLThe aim of this sheet is to perform a load balance check between long term loads (dead and SDL) verses prestressed induced moments.

The load balancing is performed by the designer who checks the flexural stresses induced by these two opposing actions, and modifies the number of strands or debonds th

Notes; These stresses are based on the girder section only for dead load and stressing loads: SDL stresses are based on the composite section

Total No of Strands 50Final long term force for one strand (fpl) 112.9 kN or 0.61 UTSConcrete Property Sections for Girder section only Composite Section

Girder depth d = 1.2 m Total section depth D = 1.400 mArea (girder) = 0.4798 m2 Area (composite) = 0.888 m2Ixx (girder) = 0.08733 m

4

Ixx (composite) = 0.209 m4

Distance to N/A from soff i t of girder y= 0.556 m Distance to N/A from soff i t of girder Y= 0.694 mZtop (girder) = 0.136 m3 Ztop (Composite) = 0.296 m3

Ztopflange (Composite) 0.413 m3Zbot (girder) = 0.157 m3 Zbot (Composite) = 0.301 m3

Determine Average Eccentricity from Soffet and total post tensioning force at each location(Tendon Forces include all short term and long term losses)Distance 0 1.50 2.99 4.49 5.98 7.48

Force Tendon 1 1355 1355 1355 1355 1355 1355Distance from Soffit Tendon 1 0.07 0.07 0.07 0.07 0.07 0.07





F T d 6 0 0 0 0 0 0


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Beca Carter Hollings & Ferner Ltd AJOB NAME: Sarawak Coastal Road JOB NO

SUBJECT: 30m girder PAGE N

BY: WEP DATE:

Summary of Final Stresses (COMPOSITE STRUCTURE)Live loads and other load stresses are derived from the composite section

Notes; The dead load and stressing stresses are based on the girder section only. The deck does not carry the compressive loads from the stressing for this assessm

Total No of Strands 50

Final long term force for one strand (fpl) 112.9 kN orConcrete Property Sections for Composite section Property Sections for Girder section Long Term Losses

Total section depth D = 1.4 m Girder depth d = 1.2 m Strand RelaxationArea (compo site) = 0.888 m2 Area (girder) = 0.4798 m2 CreeIxx (composit e) = 0.209 m4 Ixx (girder) = 0.08733 m4 Shrinka e

Distance to N/A from soff i t of girder Y= 0.694 mistance to N/A from soff it of girder y= 0.556 m Total 22Ztop (Compo site) = 0.2960 m3 Ztop (girder) = 0.135606 m3Zbot (Compo site) = 0.3012 m3 Zbot (girder) = 0.157068 m3 Equivalent Force 2

Ztopflang e = 0.4130Distance to N/A from top of girder Yt= 0.506 m

Summary of Tendon Forces Distance 0.00 1.50 2.99 4.49 5.98 7.48 8.97 10.4Total Force 4291 4291 4291 4291 5646 5646 5646 5646Average Eccentricity measured from Soffit 0.20 0.20 0.20 0.20 0.18 0.18 0.18 0.18Ave Eccentricity measured from Girder Neutral Axis 0.356 0.356 0.356 0.356 0.376 0.376 0.376 0.37

Summary - Loads(Note - positive value for positive moment) Load CaseStressing Moment Pi.e =P.S -1526 -1526 -1526 -1526 -2124 -2124 -2124 -212Girder SW +Deck DL (from sheet E ) DL 212 402 570 715 838 939 1017SDL (from sheet E) SDL 212 402 570 715 838 939 1017Live Load - Combination 1 LL1Live Load - Combination 2 LL2

0.61 UTS


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Beca Carter Hollings & Ferner Ltd

AJOB NAME: Sarawak Coastal RoadSUBJECT: 30m irder

BY: WEP

Note, this check assumes the compression stresses in the girder have creeped into the deck slab. This check is for a monolithic struc

Therefore the stresses from the P f/A, Pf.e/Z and dead load moment are based on the com osite section ro erties

Summary of Final Stresses (MONOLITHIC STRUCTURE)Total No of Strands 50

Final long term force for one strand (fpl) 112.9 kN or 0.61 UTSConcrete Property Sections for Composite section

Tota l sect ion depth D = 1.4 mArea (compos i te) = 0.888 m2Ixx (compos i te) = 0.209 m4

Distance to N/A from s off i t of g irder Y= 0.694 mZtop (Composi te) = 0.296033994 m

3

Zbot (Composi te) = 0.301152738 m3Distance to N/A from top of girder Yt= 0.644 m

Summary of Tendon Forces Distance 0.00 1.50 2.99 4.49 5.98Total Force 4291 4291 4291 4291 5646

Average Eccentricity measured from Soffit 0.20 0.20 0.20 0.20 0.18Ave Eccentricity measured from N Axis of Compos ite Section 0.494 0.494 0.494 0.494 0.514


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Beca Carter Hollings & Ferner Ltd A EXCEL WORKSHEETJOB NAME: Sarawak Coastal Road JOB NO: 9101179

SUBJECT: 30m girder PAGE NO: F

BY: WEP DATE: 5/15/2013

This sheet determines the equivalent loading, and girder deflection caused from the stressing. The deflection will be based on

the girder section properties only.

Prestress Pattern for Prestressed Girder Equivalent Moment M = P.e

Deflection = M.l2/(8EI)

End Rotations = +/-.M.l/(2.EI)

Using the total average depth for all cables and use the average force at midspan for determining deflections and end rotations

Input Ixx (girder) = 0.08733 m4

Modulus of Elast icity @ Transfer 25000 MPa

Span 29.9 m

1.744E-02

Rotation

(rad)

Stressing Load at

Transfer (midspan)

P (kN)

6769

Eccentricity

e (m)

Equivalent

2546.540.38

Moment (kNm)

130.35

Deflection

(mm)

eP

P/9101179/145581390.xls.ms_office

Page 7 of7

Equivalent load 5/15/2013 1:17 AM

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