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征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之外，这首先是由于缺少一般的优化策略和相关的设计原则。由细长桁架取代传统的混凝土结构的形式遵循力的方法明显的增强是可能的重量减轻和资源效率以及结构的透明度和美学方面的关注。在系统层面（支柱和拉杆的整体布置）和单个组件（优化的杆和连接元件）混凝土桁架上使用创新材料（例如UHPC）和智能结构的安装方法已经可以替代其他解决方案，从而显著降低腐蚀影响，从而实现高度耐用的结构构件，只需最少的维护。因此，本研究计画的主要目的是推导出一般的力学模型，以及二度与三度花丝混凝土桁架的最佳接合与设计原则。在此过程中，将开发一种模块化结构概念，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-其特征在于预制形式优化的支柱，拉杆和连接元件在现场组装到整体承载系统。在DFG优先计划的第一个资助期内（2011 - 2014年）;针对个别项目（采用UHPC和无腐蚀CFRP加固的形状优化的花丝杆，用于可变三维杆结构），推导出了材料优化的压杆和预应力受拉构件的力学模型和设计原则，这些压杆和受拉构件由超高性能混凝土和非混凝土构成，仅限金属CFRP加固和预应力。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开发有效的连接概念（节点），特别是推导系统层面的一般和设计原则（即杆和节点的总体布置）。在项目完成后，将提供经过科学验证的原理，使人们能够构想出轻质和透明的二维和三维混凝土杆结构，所需资源最少。为了验证有效性和实用性，计划在考虑到两个供资期内取得的所有相关成果和调查结果的情况下，最终建立一个全面的示范系统。该示例性结构还将用于通过实验测试来证明和检查系统的整体延展性。

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.