After the project has been given the directive to commence execution, for instance drawing approvals, then detailed planning has to be carried out. It must be determined that there will not be any new geometric changes made. The project planning basically includes detailed planning of mounting such as the cable, clamping plates, fitting plates, etc. Regarding air cushion roofs, plans for the pneumatic system (compressors and pipelines) are integral to plant planning.
Biaxial tension tests/Customisation
The structural behaviour of membranes is not linear in regards to length or cross-direction of the material rolls. In order to set up compensation for customisation, biaxial tension and elongation testing has to take place. The so-called construction unit can be used to show how the behaviour of tension and elongation can be achieved under stable condition of pre-stress.
Selection of Materials
The type of usage, external as well as legal specifications, technical requirements as well as of course the budget at hand are decisive in the choice of membrane materials. Essentially, there is a difference between vinyl coated polyesters, PTFE coated glass fabrics and ETFE screens. Based on load, types 1 to 5 of the coated stuffs can be selected based on variations in tear resistance. Tear resistance for durability against hail plays a role as well in the selection of screen thickness.
There are a series of classical forms, which have over time, become standard. In each case, type and reason for usage are decisive in determining which form is best suited. In order to arrive at an optimal solution, experience has shown that different variations have to be studied and assessed. In this phase we recommend close cooperation with the architect involved, the supporting structure specialist and the company that specializes in this type of work.
Supporting Structure Concept
Fundamentally, it must be set as to whether the primary supporting structure of the secondary supporting structure should be separated or if a definite interaction between the membrane and supporting structure inevitably should occur respectively. In general, working apart from the supporting structure is recommended. Provided that a membrane is a part of a primary supporting structure, then additional stabilizing elements should be arranged for, for instance cable bracing.
Prior to the start of plant planning, the concept for assembly must at least be in the stage of a draft. The choice of details directly has to do with the assembly concept. In assembly planning, it is of utmost necessity to secure that the assembly conditions have been analysed and can be guaranteed.
When planning membrane constructions, the following fundamental constraints and demands have to be considered:
Mode of Use
It should initially be considered whether the building project has to do with temporary or permanent usage. Examples of temporary construction are exhibition objects or projects for cultural, commercial or sports events. Accordingly, this question is concerned with construction. Should it be a closed covered building, a retractable roof, or a facade?
Based on the location of the property, the load brought on by wind, rain and snow can be dealt with in different ways. In calculating for these difficulties, the specifications as to relevant standards regarding load assumption are adequate. However, in the case of larger projects, it is recommended by means of testing the wind tunnel to calculate the form coeffience by calculating wind pressure and wind suction or at least consult a wind specialist.
Essentially, the questions as to fire prevention, building physics (acoustics), energy statics and ecology should be discussed. Hardly any standards for membrane construction exist up to now. Nevertheless, conditions specific to this issue continue to be in force as regulations for building height or the minimum distance to property limits.
Membrane constructions are spacial supporting structures for planes, that either have a curve in the opposite direction (curved space) or are curved in the same direction, Those with a curve in the opposite direction are placed in a stable state due to respectively selected preliminary tension in the length, for instance pneumatic pressure at the same time as the cross direction of the roll of membrane material. The overlapping of maximum tension for the heaviest of loads and preliminary tension are the basis for membrane assessment.