Joining and design principles for two- and three-dimensional filigree trusses constructed of form-optimized UHPC rod members and corrosion-free CFRP-reinforcement

迄今为止，混凝土承重系统的主要特点是材料的不平衡利用。除了决定性地提高几何上更有效的结构的模板和脚手架的成本外，这首先是由于缺少一般的优化策略和相关的设计原则。通过用细长桁架代替传统的混凝土结构，采用形式随力的方法，可以在减轻重量和资源效率以及结构透明度和美学方面得到明显的增强。创新材料（例如UHPC）的使用和智能结构的安装方法，无论是在系统层面（支柱和纽带的总体安排）还是在单个组件（优化的杆和连接元件）上，混凝土桁架都可能是其他解决方案的替代方案，可以显著减少腐蚀影响，从而使结构构件高度耐用，需要最少的维护。因此，研究项目的主要目标是推导出二维和三维细丝混凝土桁架的一般力学模型以及优化的连接和设计原则。在此过程中，将根据控制载荷和整体几何边界条件，开发具有可变杆和连接元件排列的模块化建筑概念，其特点是预制形式优化的支柱、纽带和连接元件组装到现场的整体承重系统中。在DFG优先项目的第一个资助期内（2011 - 2014年），单个项目（使用UHPC和无腐蚀CFRP加固的可变三维杆结构的形式优化的细丝杆），已经为材料优化的压缩杆和预应力构件推导了适当的力学模型和设计原则，这些构件仅由超高性能混凝土和非金属CFRP加固和预应力构成。基于第一期获得的结果，第二个资助期（2014 - 2017）的研究活动将集中于有效连接概念（节点）的发展，特别是在系统层面（即杆和节点的总体安排）的一般和设计原则的推导。在项目完成后，将提供经过科学验证的原理，使光和透明的二维和三维混凝土杆结构的概念需要最少的资源。为了验证有效性和实用性，计划考虑到在两个供资期间取得的所有有关成果和发现，最后建造一个全尺寸的示范装置。这个示范结构也将被用来演示和检查系统的整体延展性，通过实验测试。

So far concrete load-bearing systems are mostly characterized by an unbalanced utilization of material. Besides decisively raising costs for formwork and scaffolding of geometrically more effective structures this above all results from missing general optimization strategies and the related design principles. By substitution of conventional concrete structures by slender trusses governed by the form-follows-force approach distinct enhancements are possible in terms of weight reduction and resource efficiency as well as structural transparency and aesthetic aspects are concerned. The use of innovative materials (e.g. UHPC) and erection methods for smart structures both on system level (overall arrangement of struts and ties) and regarding the individual components (optimized rods and connection elements) concrete trusses already may be an alternative to other solutions leading to decisively reduced corrosion effects and hence to highly durable structural members requiring minimum maintenance. Therefore, the main goal of the research project is to derive general mechanical models as well as optimized joining and design principles for two- and three-dimensiona filigree concrete trusses. In doing so, a modular construction concept with variable arrangement of rods and connection elements - depending on the governing loads and the overall geometric boundary conditions - will be developed being characterized by prefabricated form-optimized struts, ties and connection elements assembled to the overall load-bearing system on site. Within the first funding period of the DFG priority program (2011 - 2014; individual project (form-optimized filigree rods utilizing UHPC and corrosions-free CFRP-reinforcement for variable three-dimensional rod structures) appropriate mechanical models and design principles have been derived for material-optimized compression struts and prestressed tension members constructed of ultra-high performance concrete and non-metallic CFRP reinforcement and prestressing, only. Based on the results gained from the first period the research activities within the second funding period (2014 - 2017) will concentrate on the development of an effective joining concept (nodes) and particularly on the derivation of general and design principles on system level (i.e. overall arrangement of rods and nodes). Following the completion of the project scientifically proven principles will be provided enabling the conception of light and transparent two- and three-dimensional concrete rod structures requiring minimum resources. In order to verify both effectiveness and practicability it is planned to finally build a full-scale demonstrator taking into account all relevant results and findings gained in the two funding periods. This exemplary structure will also be used to demonstrate and check the overall ductility of the system by experimental testing.