Relationship between probability of breakage to maximum principal stresses in window glass

Currently, the ASTM design methodology to determine the load resistance of annealed window glass incorporates a probability distribution to model glass load resistance. A probability of 8 lites per 1000 broken at the first occurrence of the design load was selected to match a load resistance consistent with a historical design factor of 2.5. The historical use of a factor relationship leads to the misconception that the design methodology follows an allowable stress procedure. The misconception has led to another common misconception among architects and engineers that a constant maximum principal stress exists, associated with the load resistance for any combination of lite thickness, aspect ratio, and surface area. This paper presents a relationship between the maximum principal stress in glass lites associated with their design loads for a probability of breakage of 8 lites per 1000. The relationship clearly shows that the maximum principal stress is not constant for a single