Calculation of prestressed structures (esas.40, esa.17, esa.20)

 

esas.40, esa.17, esa.20

This modules enables user to introduce tendons with 3D geometry and calculate losses of prestressing. It includes automatic generation of eccentric finite elements for group of tendons (tendons become a part of structural model) and calculation of equivalent load, internal forces and stresses caused by prestressing.

Strand-patterns

esa.17

Highlights
User-defined templates for prestressing reinforcement in pre-tensioned/posttensioned concrete members

Fast re-use of templates in other projects

Parameterisation of the reinforcement templates
Possible to input bore holes patterns by means of a dwg/dxf file
Asymmetrical strand patterns

Strand-patterns enable the user to quickly and easily model pre-tensioned/post-tensioned concrete members in accordance with their daily practice. The user utilises what is termed borehole and strand patterns in order to input individual strands and adjust their properties such as the initial stress, debonding length, draping distance, type of strand, etc. The user can store the borehole- and strand-patterns in libraries and retrieve them back when needed; thus attributing to a standardised company-wide solution for strand layout in members. Consequently, the application of this module in combination with the module for parameterisation provides the user with the best solution for precast pre-tensioned members.

The philosophy of what is termed a “super-user” enables the customer to assign a “super user” who can create and maintain strand patterns and individual templates/parameters. An “ordinary user” is then only able to use the templates with strand patterns created by this “super user” in a quick and easy way, without the possibility to use a noncompany strand pattern or to enter incorrect input values. The library can be stored by the “super user” on the company server and it can be even made accessible to customer’s clients through the Internet. Various data for the cross-section can be imported from DWG or DXF file, attributing to a quick conversion of old calculation practice into the new SCIA Engineer integrated solution.

The input dialogue for strand patterns is straightforward and corresponds to the needs of design practice. The user can see in one glance the centre of gravity for both the prestressing and cross-section. For asymmetrical cross-sections like T-shapes used at ends of bridges this contributes to a proper design of prestressing. The table of geometrical data calculates on-line the data related to the prestressing and cracked concrete section while the user is still inputting the strand layout. These data include, for example, the moment of inertia, area of concrete without the strands, section modulus at top fibres, etc. The user is able to easily assign debonded and draped strands. Even curved members can be prestressed using the draping functions. All prestressing materials can be used, like wires, strands and bars. This means that structures like asymmetrical T’s, hollow core slabs, double T’s, foundation piles, lattice girder slabs, and others can be modelled.

All entered data can be reviewed in the graphical window of SCIA Engineer and, if necessary, easily adapted. View parameters help the user to change the picture of the strand pattern according to the company practice; the same picture will be stored in the document. Other data available for printing include, for instance, the initial stresses, borehole patterns and strand properties. This module is used in combination with the modules “construction stages’, “time dependant analysis” and “prestress checks’. This module can NOT run without module esas.40: “calculation of prestressed structures’.

Tendons

esa.20

Highlights
Direct input of internal and external posttensioned tendons

Import of tendon geometry through DXF,DWG, XML

Export of tendons to CAD programs for the finalisation of drawings

Post-tensioned or external tendons “Post-tensioned or external tendons” allow the user to model in 3D, and in a practical way, tendons for beams, columns, walls and plates. The user can directly draw an internal or external tendon, or alternatively, he can base the design of a post-tensioned tendon on a library of standard “source” geometries. The source geometry represents a part of the tendon, e.g. the straight part at the end of the tendon, the curved part with the minimum radius above the support or the part at midspan. Source geometries can be merged together to define the practical geometry of the tendon in accordance with a common engineering practice. Tendon geometries can be also easily imported from XML, DWG or DXF files.

During the design, i.e. prior to calculation, the user can quickly review the estimate of losses, which attributes to a quick and practical design. After a successful calculation, all the relative geometry data and tendon properties can be printed in a user-friendly style. Additionally, all (geometrical) properties of the internal or external tendon can be parameterised, thus contributing to a fast and easy design of repeating or relatively standard prestressed structures.

Tendons can be defined for any type of structure: bridge, slab in a building, wall or beam. The following codes are supported: IBC, DIN, ÖNORM, CSN, NEN, ENV and the latest EN code. The tendon can be curved in the XZ-plane and/or XY-plane. Consequently, the user is capable of modelling almost any prestressed structure, whether with or without internal or external tendons.

The user can define all the necessary properties of the tendon, such as the anchorage set, initial stress, friction properties, etc. Moreover, the user can specify the method of stressing (only from the beginning, from the beginning and re-stressed from the end, etc.), and the type of short-term relaxation. Usual prestressing materials/elements like wires, strands, cables and bars are defined in the default material library. Common relaxation tables are defined by each national code and can be adapted according to the user’s or manufacturer’s requirements.

When the design of the tendon is complete,the user can export the tendon to a CAD-program for the finalisation of the drawing. The calculation document plots all necessary data, results and properties of the tendon. All relevant data are embedded in the user-perfect document of SCIA Engineer and require no extra handling at all.

The application of post-tensioning together with the module for parameterisation enables the user to define perfect templates of post-tensioned structures in an easy, practical, project-defined or company-defined way. The document is always exactly according to the engineer’s wishes or practice. Moreover, each individual document can be defined separately for each external party, so an external auditor can have a more detailed document (graphically or numerically) than a colleague. This is all changed on a click of a button. This part of the module is used in combination with the modules “construction stages’, “time dependant analysis” and “prestress checks’. This module can NOT run without module esas.40: “calculation of prestressed structures’. The whole package of prestress modules is today the best solution for the calculation of pretensioned or post-tensioned structures.

15/08/2014