Load Duration and Interlayer Thickness Effects on Laminated Glass

As part of an ongoing laminated glass research program at the Glass Research and Testing Laboratory at Texas Tech University, full-scale laminated glass laboratory specimens were tested under uniform lateral loads and simply supported boundary conditions. Effects due to varying interlayer thicknesses and long-duration (one hour) loads were observed. Interlayer thickness effects on laminated glass unit structural response were not observed to be large. Interlayer thickness effects on corner stresses were less than 10%, while center deflections were separated by less than 4%. During long-duration tests, lateral pressures of 0.2 psi (1.4 kPa) were applied to 60×96×0.280 in. (1,524×2,438×7.1mm) laminated glass units for one-hour durations at test temperatures of 72 °F (22 °C), 120 °F (49 °C), and 170 °F (77 °C). For all three test temperatures there was a modest increase in corner stress (around 20%) and center deflection (around 10%) as a function of time at load. Rates of increase in corner stress and center deflection decreased with time at load. Conversely, stresses at the center of the unit decreased slightly over the one-hour period. In all cases, theoretically derived "monolithic and layered bounds" on stresses and deflections provided realistic envelopes for all experimental data gathered in the laboratory program.