[Textile Engineering · innovative Sail Design]
FEM Design of solar panels
Tensile membranes are pre-tensioned large-span structures. Their form cannot be geometrically determined and they instead adopt a shape that is dependent upon the equilibrium of the specific internal and external forces acting on the structure.
The final definition for the shape of the finished membrane is made in our design office using a process we call analytical form finding. We use the method of determining power density, the optimisation of which allows us to identify a balanced shape for the structure using our software as part of a complex calculation process. This balanced shape is then exposed to a wide range of different load-bearing scenarios in a computer model. Subsequent evaluation of these scenarios then gives us precise data on how the structure behaves in practice.
The primary evaluation criterion during the design phase is the permanent stable positioning of the structure under all circumstances.
Ensuring this stability is one of the main reasons why we design Reckmann tensile membranes using the latest specialist software. This is why we have acquired a highly efficient combination of software modules for designing geometric, non-linear textile drainage systems and regularly update them as technology improves. Our software allows us to freely configure individual load conditions. This gives us FE calculations – within which a balanced shape is developed for every membrane – which place the awning under equalised and controlled tension at every point.
The FE calculations also give us precise information on the forces actually occurring at each individual fixing point on the membrane, statements on the deformation of the membrane when under load, an analysis of the flow of water over the membrane and, if requested, snow load scenarios.
During the design phase, conclusions will be drawn from analysing external influences (own weight, prestressing, wind, water, ice, snow) about the internal tensions and deformations, and the result optimised. Finally, when calculating textile membranes or films, the determination of cuts in preparation for manufacture also plays a role.
Textile canopy systems are made up of a supporting skeletal structure that is covered or braced with textile membranes. The support structures are typically made from steel, stainless steel or aluminium, or GFK/CFK laminates.
The difference between a simple awning and a professionally-designed tensile membrane is that the latter is not just a flat piece of material. Modern textile engineering is based on acknowledgement of the fact that textile surfaces provide extraordinary stability when deformed on 2 levels. To achieve this, we use four traditional processes; see the system images on the left.
Sun awnings and water
Sun awnings and water? Definitely an issue! It is vital that sun awning arrangements offer reliable water drainage under all weather conditions, in order to prevent the accumulation of water.
The illustrations show a water drainage scenario for a sun awning. The awning is shown from above and is depicted - as it will occur in reality - deformed under a certain wind load, and with additional rain falling on the membrane. The small grey arrows show water runoff. The length of the arrows reflects the runoff speed.
The top image shows the design initially requested by the customer. The solid hand-drawn grey line highlights an accumulation of water here. The bottom image shows the same design that we optimised using 4 supporting tubes for the membrane. These tubes ensure that the water runs cleanly over the outer edge.
This small change means that the system can now be used over the long term and in all conditions with no problems.