Stiffness of hybrid systems with and without pre-stressing

. Constructive merging of “basic” systems of different behavior creates hybrid systems. In doing so, the structural elements are grouped according to the behavior in carrying the load into a geometric order that provides sufficient load and structure functionality and optimization of the material consumption. Applicable in all materializations and logical geometric forms is a transparent system suitable for the optimization of load-bearing structures. Research by individual authors gave insight into suitable system constellations from the aspect of load capacity and the approximate method of estimating the participation of partial stiffness within the rigidity of the hybrid system. The obtained terms will continue to be the basis for our own research of the influence of variable parameters on the behavior of hybrid systems formed of glued laminated girder and cable of different geometric shapes. Previous research has shown that by applying the strut-type hybrid systems can increase the load capacity and reduce the deformability of the free girder. The implemented parametric analysis points to the basic parameter in the behavior of these systems - the rigidity of individual elements and the overall stiffness of the system. The basic idea of pre-stressing is that, in the load system or individual load-bearing element, prior to application of the exploitation load, artificially challenge the forces that should optimize the final system behavior in the overall load. Pre-stressing is possible only if the supporting system or system’s element possess sufficient strength or stiffness, or reaction to the imposed forces of pre-stressing. In this paper will be presented own research of the relationship of partial stiffness of strut-type hybrid systems of different geometric forms. Conducted parametric analysis of hybrid systems with and without pre-stressing, and on the example of the glulam-steel strut-type hybrid system under realistic conditions of change in the moisture content of the wooden girder, resulted in accurate expressions and diagrams suitable for application in practice.