tensinet symposium sofia, 15 th –17 th september 2010 specification of a round robin exercise for...

TENSINet SymposiumSofia, 15th –17th September 2010

Specification of a round robin exercise for the design of membrane structures

Prof. Peter Gosling, Dr. Ben BridgensNewcastle University, UK

TENSINet SymposiumSofia, 15th –17th September 2010

“In experimental methodology, a round robin test is a test (measurement, analysis, or experiment) performed independently several times.

This can involve multiple independent scientists performing the test with the use of the same method in different equipment, or a variety of methods and equipment.

In reality it is often a combination of the two, for example if a sample is analysed, or one (or more) of its properties is measured by different laboratories using different methods, or even just by different units of equipment of identical construction.”

What is a Round Robin exercise?

TENSINet SymposiumSofia, 15th –17th September 2010

“…

There are different reasons for performing a round robin test: e.g. verification of a new method of analysis: If a new method of analysis has been developed, a round robin test involving proven methods would verify whether the new method produces results that agree with the established method.”

Why undertake a Round Robin exercise?

TENSINet SymposiumSofia, 15th –17th September 2010

Drivers in the analysis of Membrane Structures

TENSINet SymposiumSofia, 15th –17th September 2010

TENSINet SymposiumSofia, 15th –17th September 2010

Relevant information

Mathematical representationOf uncertain quantities

Histogram

Density or distribution function

Statistics or parameters estimation

Define performance criteria

Risk evaluation

Consequence

Design decision

Material Test Experience

Finite Element Analysis (e.g.)

FORM

Data-fitting test

TENSINet SymposiumSofia, 15th –17th September 2010

Load type

Unfactored combination

Factored combination

Wind Snow Wind Snow Minimum strength (kN/m)

12.4 11.3 14.8 14.1

safety factor

6.2 6.8 5.2 5.5

Safety index ()

3.8 3.8 3.8 3.8

TENSINet SymposiumSofia, 15th –17th September 2010

CEN TC250 WG5

EUROCODE 10

CEN TC248 WG4

TENSINet SymposiumSofia, 15th –17th September 2010

TENSINet SymposiumSofia, 15th –17th September 2010

TENSINet SymposiumSofia, 15th –17th September 2010

1. The methods used in the round robin exercise may be readily incorporated into the EN as indicative analysis approaches in their own right.

2. By analysing the same membrane structures it will be possible to see how the analysis is applied to each structure case, and to be able to understand what may be expected as outputs from the analysis. This will also prove useful in helping to define the “reporting section” of the EN.

3. Data from the round robin exercise will be used to identify the material test requirements as inputs to the particular analysis approach. This will contribute to the drafting of the EN being produced by CEN248 Working Group 4 (Coated Fabrics).

4. Assist in defining the direction and activities of the TENSINet Analysis & Materials Working Group.

Benefits of a Round Robin exercise?

TENSINet SymposiumSofia, 15th –17th September 2010

Principles of the exercise

A number of “real” membrane structure projects have been proposed by contractors and consultants from across Europe specialising in the design and construction of membrane structures.

A relatively small number of projects have been selected as part of the round robin exercise.

They have been chosen to enable a range of membrane structures to be analysed combining typical support and boundary conditions.

TENSINet SymposiumSofia, 15th –17th September 2010

Principles of the exercise

Information is provided in sufficient detail for each membrane structure project so as to avoid particular types of ambiguity in the resulting design.

Certain specific information and data relating to material stiffness properties, for example, is omitted and required to be provided by the participating organisation.

The choice of data and information to provide or to leave unspecified within the round robin exercise should prove useful in providing further insights to the TENSINet Analysis & Materials Working Group concerning material stiffness data assumptions, testing needs & procedures, including timing and specification, for example. Specifying all details of the membrane structure projects would potentially limit the value of the exercise.

TENSINet SymposiumSofia, 15th –17th September 2010

Specification of the exercise – information supplied

1. Structure geometry – e.g. positions of support points, etc.,

2. Structure support definitions – e.g. masts, cables, belts, etc., as applicable,

3. Boundary conditions – e.g. simple/moment supports, fixed/sliding supports, rotational freedoms/constraints, etc.,

4. Membrane material type & grade – e.g. PVC/polyester, PTFE/glass, Si/glass, PTFE/PTFE, etc., types I I -V,

5. Supporting structure material types – e.g. steel, aluminium, timber, wire ropes, etc.,

6. Fabric orientation/patterning – warp and fill directions.

7. Fabric prestress – warp and fill.

8. Areas of fabric reinforcement (as applicable)

9. Wind load – in the form of pressures (kN.m-2),

10. Snow load – projected plan area (kN.m-2),

11. Other considerations – e.g. exo-thermal behaviour (expansion, creep, etc.),.

TENSINet SymposiumSofia, 15th –17th September 2010

Specification of the exercise – information not supplied

1. Membrane structure material stiffness data where this is not (normally) supplied as part of the specific task,

2. Supporting structure material data,

3. Seam stiffnesses

4. Stiffnesses of reinforced areas (e.g. 2 or more layers of fabric in high load areas)

5. Membrane material elasticity model.

The analysis of the membrane structure will be under the assumption of quasi static loads (e.g. peak values). Other aspects of the analysis methodology are not prescribed. They may be chosen freely, and are expected to be that which are normally used in practice by the participating organisation.

Specification of the exercise – analysis assumptions

TENSINet SymposiumSofia, 15th –17th September 2010

Task completion and reporting

The round robin exercise is proposed as a non-commercial activity. I t is intended to serve the purpose of advancing the scientific and engineering practice in the analysis and design of membrane structures. Participation in the round robin exercise is further based on the following principles:

1. Involvement in the round robin exercise is voluntary.

2. Completion of the round robin tasks are undertaken without fee and liability.

3. The completed tasks will not be used outside the remit of the round robin exercise and will not be made available in a format that could be used for design purposes by a third party.

4. The membrane structure task results will be made anonymous.

5. Reporting of results from the round robin tasks will be made using a standard form (provided) via a dedicated Analysis and Materials Working Group page on the TENSINet website.

TENSINet SymposiumSofia, 15th –17th September 2010

Task completion and reporting – assumptions, information, & outcomes to be reported

1. Details of the analysis methodology,

2. Statement of design criteria used to select the membrane material,

3. Membrane structure material stiffness data (tension & shear) used in the analysis, stating whether specific (e.g. test, database, etc.) or assumed,

4. Seam stiffness data (if) used in the analysis (e.g. test, database, etc.) or assumed

5. Stiffness data of reinforced areas (e.g. 2 or more layers of fabric in high load areas); (e.g. test, database, etc.) or assumed,

6. Supporting structure material data used in the analysis, stating whether specific (e.g. test, database, etc.) or assumed,

7. Membrane material elasticity model,

8. Assumptions made to obviate the need for specific data not provided as part of the task specification,

9. Reasons for not making use of any part of the information provided as part of the task specification,

TENSINet SymposiumSofia, 15th –17th September 2010

Task completion and reporting – assumptions, information, & outcomes to be reported

10. Magnitude and position of maximum warp stress,

11. Magnitude and position of maximum fill stress,

12. Magnitude and position of minimum warp stress,

13. Magnitude and position of minimum fill stress,

14. Magnitude and position of maximum shear stress.

15. Magnitude and position of maximum vertical membrane displacement,

16. Magnitudes and directions of all support reactions.

17. Details of design fabric.

TENSINet SymposiumSofia, 15th –17th September 2010

Membrane structure tasks – example candidate structures

TENSINet SymposiumSofia, 15th –17th September 2010

Membrane structure tasks – example candidate structures

TENSINet SymposiumSofia, 15th –17th September 2010

Membrane structure tasks – example candidate structures

TENSINet SymposiumSofia, 15th –17th September 2010

TENSINet SymposiumSofia, 15th –17th September 2010

The driver behind the inception of the Group is the linking together of testing and analysis such that each are supportive and inform each other, rather than being considered independently as is generally the current practice.

TENSINet SymposiumSofia, 15th –17th September 2010

TENSINet SymposiumSofia, 15th –17th September 2010

TENSINet SymposiumSofia, 15th –17th September 2010