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

到目前为止，混凝土承重体系的主要特点是材料利用不平衡。除了在几何上更有效的结构的模板和脚手架的成本决定性地增加之外，这首先是因为缺少一般的优化战略和相关的设计原则。通过用形状追随力方法控制的细长桁架取代传统的混凝土结构，可以在减轻重量和资源效率以及结构透明度和美观方面实现明显的增强。使用创新的材料(例如超高性能混凝土)和安装方法，在系统层面(支柱和拉杆的总体布置)和单个组件(优化的杆和连接元件)混凝土桁架已经可以替代其他解决方案，导致决定性地减少腐蚀影响，从而获得高度耐用的结构构件需要最少的维护。因此，该研究项目的主要目标是推导出二维和三维纤维混凝土桁架的通用力学模型以及优化连接和设计原则。在这样做的过程中，将开发一种模块化的结构概念，其杆件和连接元件的布置可变--取决于控制载荷和整体几何边界条件--其特点是预制的模板优化的支柱、拉杆和连接元件组装到现场的整体承载系统中。在DFG优先计划的第一个资助期(2011-2014年；单个项目(采用超高性能混凝土和无腐蚀CFRP筋用于可变三维杆件结构的形状优化的丝状筋)中，仅针对由超高性能混凝土和非金属CFRP筋和预应力构成的材料优化的受压支柱和预应力受拉构件推导了适当的力学模型和设计原则。根据第一阶段取得的成果，第二个资助期(2014-2017年)的研究活动将集中于制定有效的加入概念(节点)，特别是在系统一级(即棒和节点的总体安排)得出一般和设计原则。在该项目完成后，将提供科学证明的原则，使轻便和透明的二维和三维混凝土杆结构的概念成为可能，所需资源最少。为了验证有效性和实用性，考虑到在两个供资期间取得的所有相关成果和调查结果，计划最终建造一个全面的示范机。该示例性结构还将用于通过实验测试来验证和检查系统的整体延性。

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.