Subject of the dissertation „The behaviour of hybrid structures considering the influence of system and material stiffness “ is the analysis of the behaviour of hybrid structures and the compilation of applicable design diagrams and formulas that enable the structural engineer to find an optimal hybrid structure on the basis of defined design criteria for a certain application. In this work the term hybrid structure characterises the combination of minimum two structural systems with unequal load bearing characteristics that are each capable of bearing the loads by themselves. A main focus of this study is to identify the potential of adaptable hybrid structures by coupling these different structural systems with varying characteristics. This dissertation aims to analyse composite trusses with tension tie cables in order to control the behaviour of the hybrid structure by modifying the stiffness of the individual structural systems so that the two differing systems beam and cable sensibly complement one another. For the purpose of research the behaviour of the hybrid structure a parametric study is conducted in chapter 1. The study includes the following parameters: the truss span, the cable geometry, the flexural stiffness of the beam, the extensional stiffness of the cable and the loading. The displacement behaviour and load bearing characteristics of the hybrid systems are observed under increasing balanced and unbalanced loading. The behaviour is described in reference to the load participation of the cable which defines the assessment criterion for the load bearing characteristic that is affected by the stiffness of the individual structural systems. In chapter 2 design criteria for the selection of appropriate hybrid structures are defined and displayed in various diagrams. For the evaluation of the behaviour of the hybrid structures the criterion load participation of the cable is illustrated as the ordinate of the design diagrams. It is the basis for the diagrams described in chapter 2. Another basis is the bearing load of the systems which is an input parameter for the diagrams. The stiffness of the hybrid structures finds its way into the diagrams by regarding the allowable displacement of the system. It is displayed as the percentage of the allowable deflection of the structure over the bearing load of the system. Further criteria are the efficiency of the structure, the weight of the construction and the transparency of the hybrid structure. In terms of light weight construction a bearing structure is efficient if the used material participates in carrying the imposed loads to a great extent. The area of efficiency that is shown in the diagrams illustrates the degree of capacity utilisation of the cable and beam section. The criteria weight and transparency are displayed over the bearing load of the system. The weight of the structure is a generally accepted criterion for an economical resource management. The diagrams illustrate curves with the constant beam stiffness EI. Due to the great range of examined systems it is possible to select a hybrid structure by utilising the diagrams according to defined and weighted criteria for any cross section or material. In chapter 3 simple equations for an approximate calculation of the hybrid structures are derived. These equations enable the structural engineer in the preliminary design phase to design an optimised bearing structure for a certain application. In chapter 4 the application of the design diagrams in conjunction with the formulas is illustrated with several design examples. The diagrams in addition to the analysis in the first chapter and the equations in chapter 3 are a descriptive instrument for the structural engineer that is easy to apply. This tool enables the designing engineer in an optimal way to find an adapted hybrid structure for a certain application.