4.1 Glass is a brittle material with different time and temperature-dependent properties than other solid materials used as walkways surfaces. Therefore, the type of glass is an important consideration in the design and construction of glass treads and glass landings constructed with laminated glass.

4.2 Post-breakage glass retention is an important consideration in the design of a glass walkway system as a means of minimizing tripping, cutting/piercing injuries, or fall-through or fallout of the glass.

4.3 The structural design shall be confirmed by calculations by a licensed design professional in accordance with Section 5.

4.4 If testing is required (see 4.4.1 - 4.4.3) to verify post-glass breakage behavior of the glass walkway, the testing shall be in accordance with Section 6.

4.4.1 For laminates with two glass plies, verification testing is required.

4.4.2 For laminates with more than two glass plies, verification testing is not required provided that calculations completed in accordance with 4.3 demonstrate that the glass assembly has sufficient strength to sustain the full design load with any one glass ply broken.

4.4.3 When verifying post-breakage behavior by calculation, allowable glass stress for 10 min load duration in accordance with Table 1 shall be used for all load cases.

TABLE 1 Allowable Glass Stresses for Nominal Load Conditions

Note 1: An allowable stress reduction factor of 0.5 is recommended for disruptive surface treatments, for example, sandblasting, unless otherwise provided by the manufacturer. A glass stress reduction factor may be required for some acid etched or patterned glasses; consult the manufacturer.

Note 2: Values derived from Practice E1300, Table X9.1 (seamed edges), factored for load duration using Practice E1300, Equation X7.1, using n = 16 for annealed glass, n = 32 for heat strengthened glass, and n = 48 for tempered glass.

4.5 The manufacturer or designer of glass walkway systems shall provide installation directions and fabrication and installation tolerances of their systems.

4.6 The structural integrity of the glass walkway system after glass breakage shall be sufficient to support the design loads after any one glass ply is broken. If damage of any kind occurs, the walkway shall be cordoned off and the installation shall be inspected to ensure structural integrity and pedestrian safety of the system.