title: Welded strips as reinforcements to improve membrane structures
Creators: name: Spedini, Lorenzo
Publisher: name: TU Wien
Year: 2015
Subjects: subject: Membrane
subject: Reinforcement strips
subject: Restraining belts
subject: PVC covers
subject: Tensile structure

description: The field of this master thesis has high relevance in matter of new technical improvement design. This specific research field presents very limited existing literature. The subject of this research is to demonstrate that there is one new system to increase the stress resistance of a PVC coated polyester fabric membrane besides the well-known restraining techniques using steel cables or textile belts. This new system uses strips of the same off the shelf PVC coated membrane material welded in key locations over the main membrane cover. The application of this solution can also be for new architectural surface texture views of a membrane structure. The application of same material reinforcement strips as restraining bands for higher stress strength gives many technical advantages respect to the existing technology in terms of economical and mechanical performance. Also using this method it can be reached a better aesthetical look thanks to the elimination of the restraining steel cables substituting them with membrane reinforced strips having the same colour and finishing of the main cover. One outcome of this research is to create a new way to produce big covered membrane surfaces that can have already welded in the restraining reinforcement system. This new technique allows relevant costs savings compared to the existing reinforcement systems for both price of the materials used and for the great reduction of man hour time in the installation phase. The present master thesis is giving new knowledge with practical testing data results executed building a new testing machine. The scope of the new testing device is to check the performances of the membrane and of all the reinforcement strips under a uniaxial tension load. The new testing machine is able to give the needed correlation between stress and elongation on membrane samples with dimensions one order of magnitude wider and longer than the ones used in the common uniaxial testing machines for this specific research field. This new construction system could also reduce all the risks of the tensioning of restraining cables and of the problems of friction between the steel cables and the PVC membrane due to the different elastic modules of the materials. The result of the present research is to show in clear tables and comments that it can be achieved the increase of stress resistance welding reinforcement strips of PVC coated polyester fabric of higher type grade over the main membrane roof. It is demonstrated that the new reinforced material is behaving mechanically as an higher grade stiffer and stronger membrane type. It is shown also the performance of this new combined material in matter of percentage of resistance increase compared to the single layer membrane. In the same way is defined the reduction of deformation under stress of this reinforced material that can be used to solve many of standard problems of roofs made in tensile membrane. The main one is the ponding effect given by the elongation of the membrane under the initial load of the rain and snow. Is also presented a practical method to define the optimal placement of the reinforced strips to increase the mechanical performances of the main cover. Finally is examined the possible aesthetical effect of the reinforcements applied over well-known tensile membrane shapes.