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Terms & Conditions

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Privacy and Cookies

Data Security

Website Terms and Conditions

Software Licensing Terms


Privacy and Cookies

We may change this privacy notice from time to time by updating this page.

What information do we collect?

When you use this website, we may collect the following information:

  • the areas of the website that you visit
  • information about your computer, such as which browser you are using, your network location, the type of connection you are using (e.g. broadband, ADSL etc) and your IP address

We do this by using cookies, which are small files that help us track how our visitors use the website and enable us to understand where we can improve your experience. If you would like to find out which cookies we use and the information they track see our Cookies Policy.

Once you submit or register information through our website we will know who you are and your activities on this website and information about you and/or your company may be recorded on our systems. For example, we may ask for personal information when you download our software including:

  • your name
  • company name
  • email address
  • postal address
  • telephone number
  • country where you are based
  • Social media ID
  • your comments/questions
  • services/markets you are interested in

We may also collect personal information from telephone calls and/or other correspondence with you.

What do we do with the information we collect?

The information we capture is used for various purposes. The main purpose is to provide you with our services (whether available via the website or offline). We also use the information for:

  • website development
  • understanding how our visitors interact on the website
  • understanding what our clients are interested in
  • understanding what potential clients are interested in
  • dealing with enquiries/concerns
  • marketing our services and people to you
  • market research
  • service development
  • internal record keeping

Marketing

We would like to provide you with information about our services and other information which we think you may find interesting. We may send you such information by post, email and/or telephone, unless you have asked us not to do so.

We will not provide your personal information to other organisations for marketing purposes without your explicit consent.

If at any time you do not want your information used for direct marketing purposes, please contact us or follow the unsubscribe link in our marketing email messages.

Who do we share this information with?

We may share your personal information with companies acting on our behalf who will only use the information to provide that service. However, we will retain control of your data and any third party service provider that we use must act in accordance with our instructions. We may also share your personal information with a purchaser or potential purchaser of our business.

In some circumstances, we may have to disclose your personal information by law, because a court or the police or other law enforcement agency has asked us for it.

How to get copies of or amend the information we have collected

You may request details of the personal information that we hold about you under data protection laws. If you would like a copy of the information held about you please write to us at oasys@arup.com or at: Data Protection Officer, 13 Fitzroy Street, London, UK, W1T 4BQ. Please note that we may charge a small £10 administration fee for information requests.

If you think any information we have about you is incorrect or incomplete, please email us as soon as possible. We will correct or update any information as soon as we can.

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Data Security

We are committed to ensuring that your information is secure. In order to prevent unauthorised access or disclosure we have put in place suitable physical, electronic and managerial procedures to safeguard and secure the information we collect, including locked cabinets, electronic password protection and pass card access to buildings.

If at any point you suspect or receive a suspicious communication from someone suggesting they work for Oasys or a website claiming to be affiliated with Oasys, please forward the communication to us or report the incident by email to oasys@arup.com or in writing to Oasys, 13 Fitzroy Street, London, UK, W1T 4BQ as soon as possible.

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Website Terms and Conditions

The contents of this web site are protected by copyright and other intellectual property rights under international conventions. No copying of any words, images, graphic representations or other information contained in this web site is permitted without the prior written permission of the webmaster for this site.

Oasys accepts no responsibility for the content of any external site that links to or from this site.

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Software Licensing Terms

Terms and Conditions of Purchase

The full conditions of purchase and maintenance for all Oasys software are set out in the Oasys Software Licence and Support Agreement. All prices are subject to TAX at the current rate.

Prices and specifications are subject to change without notice – please ask for a written quotation.

Although every care has been taken to ensure the accuracy of all information contained herein, the contents do not form or constitute a representation, warranty, or part of any contract.

Superseded Versions of Terms and Conditions

Oasys keeps copies of all superseded versions of its terms and conditions.

Maintenance & Support Services

Twelve months support and maintenance is included with most products. Thereafter maintenance is typically 20% of the current sales price.

An annual maintenance service is available for most programs after the first year.

This service includes:

  • telephone/fax/email/web based support
  • free software updates available via internet download
  • personalised output header for many products

Form finding for large-span pneumatic roof cushions

Software Used on this Project

Project Overview

With particular emphasis on cable net form finding using Oasys GSA, Eindhoven University masters students Arjen Deetman and Thijs de Geode determined the optimum design. Their ultimate goal was to complement architectural design with stable structures creating minimal visual obstruction.

Pneumatic cushions are generally accepted as the best solution for covering courtyards. Structurally, however, the most effective shape for a pneumatic cushion is circular and courtyards are predominantly rectangular. Deetman and de Goede wanted to explore other options to optimise design for rectangular buildings.

Their final design proposal is a pneumatic cushion combined with a steel frame to avoid large horizontal prestress forces on the existing building. The flexible skin is an ETFE Ethylene tetrafluoroethylene layer strengthened with an orthogonal cable net. A diagonal cable net spreads the horizontal forces more uniformly over the edge of the steel frame.

The four circular shaped arches create a compression force in the arch with edge beams that are loaded in tension. By applying four corner bars a tension belt is designed that closes the system (this belt is holding the four arches together). This shape led to a minimal visual coverage of the courtyard.

At the end of this phase of the project, a final GSA model combined the two separate models for the flexible skin and the compression elements. With this combined model the behavior of the structure is more realistic and can be further improved.

How Oasys proved invaluable

Determining the span of  ETFE

The tensile strength of ETFE is relatively low, so adding a cable net is necessary for large span structures.

During the preliminary design of the cable net, four different configurations were considered. Two orthogonal cable net grids with a grid size of 2500mm and 5000mm, and two diagonal grids with a grid size of 1750mm and 3550mm. The minimum curvatures are shown in the figure. The grid size of 5000mm was rejected since the curvature is too large.

The preliminary design of the square cushion required a determinination of the stresses in the ETFE, which are related to internal pressure [p], radius [R] and ETFE thickness. However, known factors for circular (0.5) and cylindrical (1.0) domes not applicable for square ground shapes. So, with the GSA model factor of 0.63 was approximated for a square cushion. This was based on geometrical linear theory, and only used for preliminary design calculations.

Form finding of the cable net for the flexible skin

Three different form finding methods were used to define the geometry of the cable net.

  • Force density (force divided by length)
  • Soap film property (constant pre-stress)
  • Manipulation of a deformed shape

The soap film model resulted in the most constant cable forces and spread the horizontal reaction forces more uniformly. The figures show the cable forces of the three different methods that were used. Uniform loading  (air pressure) was assumed for these calculations.

Cable nets with a grid size of 1750mm, 2500mm and 3550mm were modeled in GSA with a soap film property (the 5000mm option having already bene eliminated in the preliminary design phase of the proejct). The models were loaded with three different load cases as shown in the figure.

The analyses showed that the diagonal cable net with a grid size of 3550 mm was the best. This cable net loads the compression element inside the cushion with a more constant load.   With an orthogonal cable net the compression arch would be loaded asymmetrically.

Compression element

The proposed compression element consists hollow steel rectangular hollow elements that load the edge beams in tension. By applying four bars in the corners a tension belt is designed that closes the system. This shape led to a minimal visual coverage of the courtyard.

Arches shaped with graphical form finding were compared with circular shaped arches, and different methods of connecting them at intersections were considered. Important criteria here were the stresses in the arch beam (largest profile), buckling loads, horizontal displacements and construction.

The researchers concluded that a circular shaped arch gives the lowest stresses in the arches beam. Fixed (welded) connections give by far the largest buckling load of the total structure.

What’s next?

For this project the assumption was that the internal air pressure of pneumatic cushions was constant. In reality the air pressures varies. For further research, it will now be interesting to study the dynamic behavior of this large span pneumatic cushion, including a parameter study. 

A winning paper in the Oasys Project of the Year 2016 Competition. This design project was part of the master track Structural Design at Eindhoven University of Technology. The authors would like to thank their supervisors, Patrick Teuffel and Arjan Habraken, for their help and motivation during this project. Additional thanks to the other students of the design studio: Lieneke van der Molen, Jasper van Alphen and Jing Cui.

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