Are you looking for ASTM C 158 or looking for general idea of glass flexure strength?
I am not too familiar with american codes, but the Germans use DIN18008, while in Canada we have CAN/CGSB 12.20 M89.
According to CAN/CGSB 12.20 M89, annealed glass generally have 20MPa base tensile strength, with reduction factors due to size & edge.