pre stress
TRANSCRIPT
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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
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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
Distance from Soffit Tendon 3 0.17 0.17 0.17 0.17 0.17 0.17 0.
Force Tendon 4 1625 1625 1625 1625 1625 1625 16
Distance from Soffit Tendon 4 0.22 0.22 0.22 0.22 0.22 0.22 0.
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
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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
Force Tendon 2 0 0 0 0 1355 1355Distance from Soffit Tendon 2 0.00 0.00 0.00 0.00 0.12 0.12
Force Tendon 3 1355 1355 1355 1355 1355 1355Distance from Soffit Tendon 3 0.17 0.17 0.17 0.17 0.17 0.17
Force Tendon 4 1355 1355 1355 1355 1355 1355Distance from Soffit Tendon 4 0.22 0.22 0.22 0.22 0.22 0.22
Force Tendon 5 226 226 226 226 226 226Distance from Soffit Tendon 5 1.14 1.14 1.14 1.14 1.14 1.14
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
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Equivalent load 5/15/2013 1:17 AM