FAQ

Sheet Length – the dimension parallel to the ribs of the sheet

Sheet Width – the dimension perpendicular to the ribs of the sheet

Deflection – the distance at the midpoint of the sheet area between a state of no load and after load is applied

Rafters – Beams in a construction, which support the purlins and in many cases support directly the sheets along their sides (parallel to their ribs)

Purlins – Beams in a construction, which support the sheets along their width (perpendicular to their ribs)

Distance between Rafters or sheets supported – the distance measured from the center of one rafter or the sheet support to the adjacent one

Distance between Purlins – the distance measured from the center of one purlin to the adjacent one

The deflection at which the sheet pops out from inside the profile is referred to as the Pop-out Deflection value. Pop-out failure depends solely on the shortest dimension of the sheet (in most cases, this is the width of the sheet) and the glazing depth of the sheet in the profile (for further explanations, see Sheet Connection Within Profiles and Desired Glazing Depth under Preferences).

Under long-term load (i.e. snow), the sheet may initially deflect to a depth that doesn’t cause the sheet to pop out of the profile, but under constant load, a creep effect can result in an increase in deflection over time, which can eventually reach Pop-out Failure

The deflection at which the sheet pops out from inside the profile is referred to as the Pop-out Deflection value. Pop-out failure depends solely on the shortest dimension of the sheet (in most cases, this is the width of the sheet) and the glazing depth of the sheet in the profile (for further explanations, see Sheet Connection within Profiles and Desired Glazing Depth under Preferences).

Under long-term load (i.e. snow), the sheet may initially deflect to a depth that doesn’t cause the sheet to pop out of the profile, but under constant load, a creep effect can result in an increase in deflection over time, which can eventually reach Pop-out Failure

If we increase the width of the sheet (which is connected to the construction on all four sides), the result will be that the load required to reach the same deflection will decrease incrementally as the sheet width increases. After a certain, critical width, the load will not need to change at all in order to reach the original deflection level, and the rafters along the length of the sheets will not contribute to the sheet’s support

If, for example, we take a square sheet (equal in length and width), which is supported at all four sides by a steel frame, and apply a load of a certain type, this will cause the sheet to deflect. Now, let’s keep those same connection parameters and increase the length of the sheet, then apply load to get the same deflection as before. We’ll find that, up to a specific, asymptotic sheet length, the load required to reach the same deflection will gradually decrease.

Once this asymptotic sheet length is exceeded, no changes in the load level will be required to reach the original deflection level. Thus, we can conclude that when exceeding a certain sheet length, the purlins that support the sheets along their width do not contribute to the sheet’s resistance to bending, and as such are unnecessary. Under these circumstances, we can say that the sheets perform as if they were connected to the construction in a Side/Side Configuration. 

In some sheets, “bubbles” are formed when the lower wall of the sheet is compressed under loads or a too small cold bent radius. These bubbles disappear when the load is removed or when the cold bending is released and leave no mark on the sheets. This phenomenon becomes an aesthetic problem when the sheet functions as a skylight or other arched application. This problem should not occur if the minimum radius limits are maintained.

When a sheet which is attached within a frame is subjected to a heavy load, it can develop a wave-like deformation along its widthwise axis and the sheet walls will buckle. This is called Elastic Buckling because once the load is removed, the sheet will return to its original condition without incurring any permanent damage.

If we continue to increase the load level, the sheet will deflect until it finally buckles(Plastic Buckling) causing permanent damage to the sheet. The deflection point at which a sheet buckles is referred to as the Buckling Deflection, and is a function of the geometric structure of the sheet and the amount of material it comprises. Under Long-term load, the sheet may initially deflect to a depth that doesn’t cause the sheet to buckle (either Elastic or Plastic), but under constant load, the creep effect can cause an increase in deflection over time, which can eventually lead to Buckling Failure.

If we take a sheet connected in any configuration and apply extreme load, the sheet will either buckle and be permanently damaged, or else it will pop out from inside the profiles.

  • Polygal Standard– designed for most roofing and glazing applications, double and triple wall design provides a strong and flexible solution for all glazing applications.
  • Polygal Selectogal– Selectogal panels offer significant natural energy savings by controlling the amount of light and heat penetrating into the structure. Exclusive to Polygal.
  • Polygal Titan– Where extra strength and durability are required, Titan is the solution.
  • Polygal Titan Sky– Strength, extra insulation (U = 2.08), less weight.
  • Polygal Primalite– Novel sheet selectively reflects a large portion of the Near Infra-Red solar radiation, while transmitting more of the visible light. Keeps interiors cooler.
  • Polygal Polycoolite (Primavert)– A special pigment creates a cooler interior environment than standard opal ice color. An excellent choice for garden centers, greenhouses, and sun rooms.
  • Polygal Polyshade– Aluminum powder integrated into the exterior surface provides shade while allowing 18% light transmission. An excellent choice for bus shelters, car ports etc.
  • Polygal Thermogal– 25mm, 32mm, 35mm, 40mm – Unique inner x-brace structure provides extra strength, rigidity and outstanding insulation.
  • Polygal Triple Clip System– 16mm System represents the latest development in easy to assemble and D.I.Y. roofing systems.
  • Polygal Hurricane Panel– This protection system uses off the shelf components which benefits the customer with a low cost alternative to other hurricane protective systems.

Polycarbonate connection systems.

Aluminum 6-16 glazing system for sheets 6mm to 16mm thick. This is an all purpose economical aluminum system.

Aluminum 6-35 glazing system for sheets 6mm to 35mm thick. This is a stronger and more “beefier” system than the 6-16 system.

Always call Customer Service to check available lengths, colors and stock availability – support@plazit-polygal.com

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