Page Comparison

This\\
page provides information on how the program
{new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} Software calculates prestress losses based on the loss parametersaccording supplied byto the user. Frictionfriction and anchorage loss parameters are specified. byLosses thefrom user and the program calculates losses that are applied to both tendons modeled as loadselastic shortening and tendons modeled as elements. The other losses (due to elastic shortening, creep, shrinkagelong-term effects, including [creep|kb:Creep], [shrinkage|kb:Shrinkage], and relaxation), are computed by the analysis for tendons modeled by elements or they are directly specified by the user for tendonsfor [tendons|kb:Tendon] which are modeled as objects, and may be specified for those modeled as loads.
When
tendons\\
are modeled as elements, these other losses specified by the user (if any) are applied in addition to the losses computed by the analysis.

*On this page:*

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h1. Overview

The prestress losses which may be accounted for inwithin [SAP2000|sap2000:home] caninclude be classified as followsthe following:

* short termImmediate losses (immediate losses that which occur before and during transfer):
** anchorageAnchorage set (anchorage slip losses)
** elasticElastic shortening
** frictionFriction losses,loss due to length (or wobble) effect and curvature effects
effect
* long Long-term losses:
** due to concrete creepConcrete [creep|kb:Creep]
** due to steel relaxationConcrete [shrinkage|kb:Shrinkage]
** dueSteel to shrinkagerelaxation


h1. Short-term losses

Short Term Losses-term losses are described as follows:


h2. Anchorage Setset
Losses
Slip Thefrom anchorage set slipsetting is specifieda by the useruser-defined parameter. LossesThis dueloss tois anchorage set slip are NOT not uniformly distributed along the entire length of the [tendon|kb:Tendon]. Rather, the length ofInstead, the tendon affected by anchorage setlength is calculated as a function of thefriction loss frictionas lossesfollows:

L{math~}L_set{set~} = √ sqrt(({Delta_{setΔ{~}set{~} A_{~}PS{~} E_{~}P{~} / P)){math}

where,:

* Δ{math~}Delta_{set}{math~} = Anchorageanchorage set

* A{math~}A_{PS}{math~} = Crosstendon cross-sectional area
of
the tendon

* E{math~}E_P{math~} = tendon Young’selastic modulus of the tendon

* {math}P{math} = frictional loss expressed as a change in force per unit length, calculated from a tendon -force variation diagram

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*Related emailsEmail:*
* anchorageAnchorage set losses: email-090423 (rs→ok)(RE: Aboutregarding the tendon force loseloss problem in SAP2000 V12)
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h2. Elastic shortening
Shortening
Losses from Elasticelastic shortening lossesare areautomatically computed byfor thetendons analysiswhich forare tendons modeled as elementsobjects.


h2. Friction losses
Losses
Tendon Dueforce tois frictiongreatest betweenat the jacking tendonend, and thedecreases ductwith duringdistance jacking,from the tendonend forcebecause atof the friction jackingwhich endoccurs isduring greaterjacking thanbetween the tendon force as some distance away from the jacking end. The frictionand the duct. Friction loss has two components, parts:including the length or *wobble effect* and the *curvature effect*. TheTendon tendon force P{math~}P_x{math~} at the distance {math}x{math} from the jacking end can be expressed as follows:

P{math~}P_x{~} = P_0  e^-(mu alpha{~}0{~} e{^}-(µ α + K x){math^}

where:

* P{math~}P_0{math~} = tendon forcesforce at the jacking end
* {math}mu{math}µ = curvature friction coefficient
* {math}alpha{math}α = cumulative angle (in radians) byof whichchange tangent toin the tendon-profile profiletangent hasbetween changedx betweenand the jacking end and location x
* {math}K{math} = wobble friction coefficient
* {math}x{math} = distanceposition along tendon from jacking end to point under
consideration

h1. Long-term Termlosses
Losses
To Allevaluate long -term losses require to run staged construction, [staged construction|kb:Staged construction] must be run with dependent material properties and the losses are automatically calculated by the analysis based . Based on the material model selected for the time-dependent behaviorbehaviors forassociated concretewith creep, concrete shrinkage, and steel relaxation, long-term losses are automatically calculated.


h2. Concrete Creep Lossescreep

The followingmaterial materialmodel modelsavailable can be considered for concrete creepto [creep|kb:Creep] behavior is as follows:

* Ceb-Fip Model Code 1990


h2. Concrete Shrinkageshrinkage
Losses

The followingmaterial materialmodel modelsavailable can be considered for concrete shrinkageto [shrinkage|kb:Shrinkage] behavior is as follows:

* Ceb-Fip Model Code 1990


h2. Steel Relaxation Lossesrelaxation

The following material modelsmodel canavailable beto consideredsteel forrelaxation prestressingis steelas relaxationfollows:

* Ceb-Fip Model Code 1990


h1. References

* Deepak Choudry: Choudry, D. _Analysis of Curved Nonprismatic Reinforced and Prestressed Concrete Box Girder Bridges_, Berkeley: ReportUniversity No. UCB/SEMM-86/13, December 1986 (contains equations for tendon losses)
* [Ceb-Fip Model Code 1990 | of California, Berkeley, 1987. Print.

* {new-tab-link:http://openlibrary.org/books/OL7866640M/Ceb-Fip_Model_Code_1990]1990}Ceb-Fip Model Code 1990{new-tab-link} Telford, 1993. Print.