Zur Bemessung von SL-belasteten Anschlüssen im konstruktiven Glasbau
- Contribution to the design of lapped glass joints with bolts in bearing
Baitinger, Mascha; Feldmann, Markus (Thesis advisor)
Aachen : Publikationsserver der RWTH Aachen University (2009)
Dissertation / PhD Thesis
Aachen, Techn. Hochsch., Diss., 2009
For the design of glass structures the connection method is of great importance since the relevant stresses of point-fixed glass occur in the ultimate vicinity of the holes. If no further constructive means are provided, these stress peaks cannot be dissipated with subsequent glass breakage. This phenomenon also applies for in plane glass connections with bolts in bearing, where bolt forces act on the glass through ductile interlayers (mortar) that are placed between the glass and the steel bolt. However, until today, there are no construction standards for connections with only one bolt as well as for connections with several bolts under combined sectional forces and moments. Furthermore, imperfections, tolerances, brittle behaviour and scattering of the material properties have to be considered. This thesis addresses developing an engineering model for lapped glass joints with bolts in bearing and the derivation of rules for the design. Based on the stress function of Airy an analytical calculation method could be developed, in which local bearing stresses under bolt loading are superposed by net section stresses. Both stress states can be described by stress functions. Thus any bearing condition is addressable. By means of reverse composition of the two stress fractions the stress-strain-state of panes consisting of elastic-isotropic materials with arbitrary hole pattern under any boundary condition can be determined depending on the bolt load, the pane thickness, the hole diameter and the relevant width resulting from the joint geometry. Further the analytical solution could be reduced to a simple design equation, which enables the determination of the relevant stresses depending on bolt forces acting on the single hole, the diameter of the hole and the glass thickness. Thereby also the influence of the erection and fabrication tolerances as well as design parameters had to be systematically examined by Finite Element calculations that had been performed so far for the first time. The effects could be numerically discovered and coefficients for the design equation could be derived. Also a non uniform bolt force distribution has to be taken into account for long bolt rows parallel to the force direction. To ensure a sufficient load bearing capacity of the entire detail, the interlayer material cannot be neglected. Therefore, theoretical examinations were performed. The effect of erection and fabrication tolerances as well as geometrical parameters on the stresses in the mortar could be determined. The results serve as an approach for the verification of the interlayer against the bolt forces, the diameter of the hole and the glass thickness. The definition of the material resistance bases on former research results and examinations. All theoretical studies were verified by numerous experimental tests under monotony loading after prior cyclic service loading. In analogy to the analysis, the tests have been realised for joints under normal forces as well as under combined shear forces and moments. The stress-strain-distributions, which were determined by strain gauges and the analysis of the fracture pattern coincide with the theoretical results. Finally, it was shown that effective resistant stresses governing the load bearing capacity of bolted connections under in plane loading is lower compared to those effective resistant stresses that control failure in case of plate loading. The thesis closes with derivations for partial safety factors and proposals for the codification.