James G. Soules, P.E., S.E., P.Eng., F.ASCE ; Stephen M. Morse, Ph.D., P.E., M.ASCE ; and H. Scott Norville, Ph.D., P.E., F.ASCE
Model building codes and standards in the United States find their bases in a probabilistic model of glass load resistance (LR). In general, architectural flat glass design predicated on these model building codes and standards is restricted to rectangular glass lites continuously supported along one, two, three, or four sides.
When a design professional wishes to use glass with an odd shape (i.e., a nonrectangular shape), design procedures in the model building codes and standards regress to a maximum stress approach. A maximum stress approach to design represents a much different philosophy than does the probabilistic approach.
When compared to the probabilistic approach, designs based upon a value of maximum allowable stress may result in much less efficient design. Therefore, the need exists for a design approach for odd-shaped glass lites that has a probabilistic basis for glass load resistance. The primary analysis tools available to engineers today are based on the finite-element method and can be applied to a wide range of different glass lite geometries.
The authors developed a nonlinear finite-element model and applied the glass failure prediction model (GFPM) to the nonlinear finite-element model output to determine probability of breakage for combinations of selected flat odd-shaped glass lite geometries and loads.
The authors compared the LR of the odd-shaped glass lites to the LR of flat glass lites with the LR of rectangular glass lites having the smallest dimensions so that they would encompass the odd-shaped lites.
The authors also compared the maximum principal stresses determined for the flat odd-shaped glass lites (loaded with a pressure equal to the LR of the flat odd-shaped glass lites) from the nonlinear finite-element model to recommended values of maximum allowable stress from model building codes and standards.READ MORE