Delegated Design in Specs for Glazing SystemsWe've been asked to review several engineering company’s calculation packages and found engineers
stamping calculations that don’t meet specifications and code requirements. Please check your calculation packages to be sure.
- DL of the frame was not taken into consideration (flexure/axial load interaction) Typical C-Beam Calculations did not include axial load interaction with flexure required by the Aluminum Design Manual
- Corner location analysis (75% WL acting simultaneously). Bite loss or movement into glazing pocket was not checked. Analysis of corners for 45 degree orthogonal loading was not considered as required by ASCE 7. Important for bite loss at the glazing pocket.
- No Jam/perimeter mullion deflections to check caulking requirements. Deflections at Jamb perimeter joints were not checked for appropriate joint design. Important for preventing leaks at curtain wall interface to the structure.
- LL movement was not taken into consideration at all. Building structural live load movement and system thermal expansion was not accounted for in joint design, splices and glazing pockets. This is required by contract specifications as part of the delegated design.
- Analysis of local buckling modes and lateral torsional analysis was omitted but is required by the Aluminum Design Manual.
“If undone, you are buying calculations half done and not according to code requirements.”It may be tempting to overlook it and we understand some contractors will simply say, "It's not worth the effort." Just keep in mind that these calculations are a part of the “delegated design” required by contract documents. If left undone, glazing contractors, general contractors, AEs and the building owners are buying a design half done and not according to code requirements.
“Half done calculations may result in glass breakage, joint leakage, system failure or other liability.”Half done calculations may result in damage such as glass breakage, joint leakage, system failure or other liability that quality service providers choose to steer clear of.
Let’s work together to design systems fast, affordable and correct.
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