Cross laminated timber (CLT), as a structural plate-like timber product, has been established as a load bearing product for walls, floor and roof elements. In a bending situation due to the transverse shear flexibility of the crossing layers, the warping of the cross section follows a zigzag pattern which should be considered in the calculation model. The Refined Zigzag Theory (RZT) can fulfill this requirement in a very simple and efficient way. The RZT, founded in 2007 by A. Tessler (NASA Langley Research Center), M. Di Sciuva and M. Gherlone (Politecnico Torino) is a very robust and accurate analysis tool, which can handle the typical zigag warping of the cross section by introducing only one additional kinematic degree of freedom in case of plane beams and two more in case of biaxial bending of plates. Thus, the RZT-kinematics is able to reflect the specific and local stress behaviour near concentrated loads in combination with a warping constraint, while most other theories do not. A comparison is made with different methods of calculation, as the modified Gamma-method, the Shear Analogy method (SA) and the First Order Shear Deformation Theory (FSDT). For a test example of a two-span continuous beam, an error estimation concerning the maximum bending stress is presented depending on the slenderness L/h and the width of contact area at the intermediate support. A stability investigation shows that FSDT provides sufficiently accurate results if the ratio of bending and shear stiffness is in a range as stated in the test example. It is shown that by a simple modification in the determination of the zigzag function, the scope can be extended to beams with arbitrary non-rectangular cross section. This generalization step considerably improves the possibilities for the application of RZT. Furthermore, beam structures with interlayer slip can easily be treated. So the RZT is very well suited to analyze all kinds, of shear-elastic structural element like CLT-plate, timber-concrete composite structure or doweled beam in an accurate and unified way.
Glued glass front constructions have long been in use and are generally considered the state of the art. However, with these solutions the glass serves no stiffening or bearing function, but merely functions as an outer cover. The objective of several research projects was to investigate alternative constructions of stiffening glass fronts, which replace St. Andrew’s cross wind bracings and costly frameworks. To this end, the Department of Structural Design and Timber Engineering (ITI) studied and optimized the load-bearing capacity of these existing construction components and subsequently developed simple calculation and sizing concepts. Based on the results of the research project „Timberglass composites: calculation and sizing concept (HGV III)“ the ITI coordinated the follow-up international research project “Load bearing timber-glass composites (LBTGC)” within the framework WoodWisdom-Net. In consideration of its long-term behavior and practical application, the objective of the research project LBTGC was to develop “stiffening timber-glass composite (TGC) structures”. With the purpose to meet the highest standards of cost effectiveness, alternative stiffening TGC constructions for multi-story buildings were investigated. This paper illustrates these developments.