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Designers of architectural glass in the United States rely on model building codes and standards for definitions of load resistance (LR) and other factors pertinent to design. Unfortunatel...

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 t...

This study investigated the effects of inorganic silicone coatings on the load resistance of heat treated glass beams. The authors performed destructive load tests on 192 heat treated glas...

The authors tested five full scale samples of nominal 6 mm thick heat strengthened glass to failure under uniform lateral loading. One sample was clear glass, one sample had full coverage ceramic enamel frit, and the other three samples had ceramic enamel frit patterns with different percentages of coverage. In testing the samples with ceramic enamel frit applications, researchers oriented the specimens to place the ceramic enamel frit in tension under lateral loading. The authors found that the samples with ceramic enamel frit displayed considerably lower magnitudes of load resistance than did the clear heat strengthened sample. In addition, the authors noted that every fracture origin they have inspected to date from the 75 specimens with ceramic enamel frit patterns occurred underneath frit. Micrographs of fracture origins indicate that the frit may actually damage the glass surface during the heat strengthening process. This study has significant implications for architectural glass design.

In the past few decades, designers increasingly work on glazing projects across the world requiring the use of international glazing standards that often differ from the designer’s national code. Commonly specified international glazing standards include prEN16612, AS1288, and ASTM E1300. Each of these standards has a different approach to determine window glass strength. This paper explores one aspect of glazing design for insulating glass units, the method for estimating the load sharing between the lites comprising insulating glass units. Each glazing standard uses a different method for estimating load sharing and how the effects of environmental loads are incorporated into the estimation. Environmental loads include but are not limited to changes in atmospheric pressure, resulting from elevation, climatic, and temperature variations. Additionally, several iterative methods appear in technical literature that attempt to account for most known factors affecting insulating glass load sharing. Each of these methods addresses environmental loads differently with differing degrees of accuracy. This paper presents comparisons between the three glazing standards above and an iterative method for load sharing with environmental loads in double and triple glazed insulating glass units. The major factors varied in the investigation are insulating glass unit constructions, dimensions, glass lite thicknesses, air space thickness, temperature and pressure and atmospheric pressure changes due to elevation change. Pressure versus load sharing percentage curves are presented for select double and triple insulating glass unit constructions. Figures in this paper will show the load sharing trends of different similarly loaded insulating glass units due to varying the pressure differential between the air space(s) and atmospheric pressures. The results of this study will indicate differences between the load sharing methods and provide example scenarios where the methods produce similar and different estimates of insulating glass load sharing.

The authors performed an experimental study with weathered fully tempered monolithic glass loaded to failure under controlled conditions. The 14 specimens in the study originated from the northeastern United States. The specimens were loaded with monotonically increasing pressure until fracture occurred in accordance with the ASTM E997 test method. The recorded failure load time histories were converted to equivalent 3-s failure loads using a modified load-transformation-integration method that incorporates residual compressive surface stress. Variations of the residual compressive surface stress measurements are presented for each specimen, and the effect that the variations in residual compressive surface stress have on the equivalent 3-s failure load calculations are also explored. Equivalent 3-s failure loads are shown to be proportional to the measured residual compressive surface stress. The equivalent 3-s failure load is compared to the load resistance calculated using ASTM E1300, and the m...

Data were studied from tests of new and weathered rectangular annealed glass samples, each consisting of numerous specimens, loaded to fracture. The maximum principal tensile stress at the fracture origin was compared with the single largest maximum principal tensile stress (SLMPTS) within each specimen. The findings indicated that maximum principal tensile stresses at the fracture origins were always less, often significantly so, than SLMPTS in the specimens. In addition, fracture origins rarely, if ever, coincided with the location of SLMPTS in a rectangular glass lite specimen. These results support the notion that glass thickness selection should not be based on a maximum principal stress method.

ASTM E 1300-07 employs only two glass type factors to adjust the load resistance of annealed glass for heat treatment, one factor for heat-strengthened glass and one factor for tempered glass. The use of only two factors provides a simplistic approach that fails to utilize the full capacity of heat-treated glass. ASTM E 1300-07 differentiates heat-strengthened from fully tempered glass by the magnitude of the residual compressive surface stress resulting from the heat treating process. Furthermore, ranges of residual compressive surface stress are specified for both heat-strengthened and fully tempered glasses, suggesting the glass type factors should vary with the residual compressive surface stress. This article presents a rational method for determining the load resistance of heat-treated glass based on the residual compressive surface stress. A method incorporating previously accepted design principles with the addition of extensive data computation is advanced to calculate load resistance for heat-tr...

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 1,000 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 the relationship between the maximum principal stress in glass lites associated with their design loads for a probability of breakage of 8 lites per 1,000. The relationship clearly shows that the maximum principal stress is not constant for a single lite thickness for varying rectangular dimensions much less for all lite geometry combinations. A series of charts illustrates the trends in magnitude and location of the maximum principal stress as a function of lite thickness, aspect ratio, and surface area.

In the published article, Table 8 is incorrect (the last value in column 2 and all numbers in column 3). The correct table is given below

ASTM E1300-09 uses a glass failure prediction model (GFPM) to quantify the probability that a critical surface flaw with a certain location and orientation will initiate a facture in the glass for a given lite geometry and uniform design load. The nonfactored load charts in ASTM E1300-09 are calibrated to a GFPM probability of breakage of 8/1,000 (0.008) at the first occurrence of the design load. The GFPM probability of breakage only addresses the material properties of the annealed monolithic window glass and does not incorporate the probability of the occurrence of the design load. Because window glass is typically designed to resist wind loads, the probability of the occurrence of the design load was based on ASCE 7-05. Using a Monte Carlo simulation to evaluate the limit-state equation, this paper presents a procedure to quantify the probability of failure incorporating the probability of the wind load and the probability of the window glass load resistance from the GFPM for window glass lite...