Prestress / post-tensioning

Prestress / Post-tensioning

Model post-tensioned structures more accurately with shells as well as using beams or volumes, and incorporate time-stage with creep and shrinkage.


Span-by-span, progressive placement, balanced cantilever and incremental launching time staged construction methods are supported.


Use the post-tensioned bridge wizard to generate a box girder as constructed by the "Free Cantilever Method".

Prestress modelling

Define tendon profiles and properties

Define tendon profiles either manually, by copying and pasting data from a spreadsheet, or from selecting by selecting lines, arcs or splines that are defined or imported into LUSAS Modeller. 


Define tendon properties and allow for elastic shortening due to stressing of other tendons according to the design code, or specify user-defined percentage losses to be taken into effect. For design codes that support it, time dependent effects can also be considered.

Define and assign tendon loading

Reference tendon profile and tendon property data in a tendon loading  attribute and define a specified prestress force and associated jacking and loss details. Anchorage losses can be defined as slippage from either, or both ends. 

Assign tendon loading to selected lines, surfaces or volumes in the model. Tendon loading assignment options state how the tendon loading is to be applied and, for assignment to lines, mapping and offset options can be used, as well as specifying in which loadcase(s) the tendon loading should apply.

Visualise tendon profiles

View the defined tendon profiles within a fleshed or unfleshed model.

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Watch how to define and assign the a tendon loading attribute (which references tendon profile and tendon properties) to selected features in a box girder bridge that is modelled using shell elements. (Version 19)

Easily view and edit prestress (and other) attribute assignments

  • View the assignment data for any assigned attribute in a spreadsheet-style format. 
  • Easily check, or modify, what load is applied, where it is applied, which loadcases it appears in, any load factors. The assignment grid makes it easier to spot mistakes and put them right.
  • Copy and paste data to and from spreadsheets.
  • Over-write data for all assignments (such as changing all the load factors for all load assignments) in one go.

Easily view and edit multiple prestress (and other) load attributes

Use the new Attributes editor to easily edit prestress loading data (and other structural loading data) in one place, when two or more of the same loading type is selected for editing.  

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Watch how to use the loading attributes editor and the attributes assignment dialog to make individual changes for multiple selections.

An incorrectly entered tendon force for a post-tensioned model is shown to be easily spotted and corrected. 

Then, for a different model, by copying and pasting dynamic load factors from a spreadsheet to replace constant values used by a moving load, it is shown that the dynamic effect of a tank crossing a structure can be modelled.

(Version 19)

Creep and Shrinkage material models

Calculate time-dependent creep and shrinkage losses in accordance with supported design codes:
  • AASHTO LRFD 5th-7th editions
  • CEB-FIP Model Code 1990
  • EN1992-1-1:2004 Eurocode 2
  • fib Model Code 2010
  • IRC112-2011
  • JTG 3362-2018
All creep and shrinkage material models can be used with beam elements, 2D/3D continuum elements, semi-loof and thick shells, and composite solid elements. Whilst, for all, creep and shrinkage is only strictly applicable to beams, in LUSAS the creep equations have been extended to 2D and 3D stress states.

Solve and report on results

Solve for prestress loading as part of solving a model. 

Graph prestress losses

Graph short (instantaneous) and long-term losses for individual or sets of tendons for a range of construction stages / loadcases.

Report on prestress data

Report on all prestress data by adding a Prestress chapter to a model report. 

View tables of tendon summary data, tendon profile data (original and from sampling points), prestress losses for each tendon.

Obtain tendon profile setting-out data for a defined spacing for use on-site,  with reference to vertical and horizontal origins.

Use your results output to assemble a complete report for your checker or your client. It now supports graphical views, tables, graphs, design calculations and user content.  
 
If you modify the model, the input and prestress data and results will update. Let LUSAS generate the same report again with a few clicks.  
 
Save the report template and share it to produce quality standardised output across your design teams and offices.

Time management

Use the time management facility to manage a simple construction schedule and easily adjust the duration of pre-defined construction stages in a staged construction analysis.

Automatically update the total response time values in nonlinear and transient controls that have been previously specified for each loadcase of a staged construction analysis. 
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