Technical area

Ningbo Zhongding Plastic Co., Ltd.


Technical area

Pc endurance plate (solid plate) wind and snow load bearing parameters

C solid board (PC endurance board) bearing capacity, wind and snow load

About conventional lighting window shape and size ratio:
Daylight window panes come in many shapes, with quadrangles being the most common, usually rectangular. The size ratio of the four sides (width) a and (length) B of the rectangle is a critical condition for determining the load-bearing capacity of the lighting window pane (or any planar load-bearing member).
When a = B (I. e. square), all four load-bearing sides of the lighting window equally share the load, which is the best solution for the shape of the pane. The stiffness and bearing strength of the lighting window is best in both directions. In fact, the circular lighting window because there is no far corner so the performance is better.
As the ratio of a: B becomes smaller, (such as 1:1.5), the impact of more support on the load-bearing capacity of the lighting window is getting smaller and smaller, until when a: B = 1:2, the short side has only a slight impact on the load-bearing capacity of the lighting window, which can be ignored. In the case of such a length-to-width ratio, it can be considered that the lighting window is only supported by the two long sides and the end of the long side, and the latter can only be regarded as an additional safety supplement.


Regarding the load-bearing capacity of lighting windows fixed on four sides, three sides and two sides:
In fact, the lighting window not only needs to be supported, but also needs to be firmly clamped (fixed) along its edge. Clamping and fixing have a significant effect on the load-bearing capacity of the lighting window. The daylighting window, which is clamped and fixed on all four sides, has the greatest load-bearing capacity. The reduction in the number of sides for clamping and fixing reduces the load-bearing capacity of the lighting window. If the design only requires two or three sides of the lighting window to be clamped and fixed, the thickness of the lighting window should be increased or the allowable span should be reduced.
Table A. Table of wind/snow loads. Conditions: plane, four-sided fastening, single-layer plate, single span.
Maximum recommended span between supports for daylighting windows with different aspect ratios under increasing (from light to heavy) wind/snow loads (for shorter size daylighting windows):
Thickness mm uniformly distributed wind/snow load Kg/㎡ Maximum Support Span of Endurance Plate with Different Aspect Ratio & Width of Lighting Window (mm)
Width to length ratio 1:1 to 1:1.2 Width to length ratio 1:1.2 to 1:1.5 Width to length ratio 1:5 to 1:1.8
4 50 1200 1150 1050
80 1150 1050 1000
120 1080 1020 920
150 1020 980 880
200 980 880 800
6 50 1650 1580 1520
100 1480 1420 1350
150 1320 1250 1180
200 1200 1120 1020
250 1080 980 880
300 920 850 750
8 50 2050 1920 1780
80 1820 1750 1620
120 1750 1620 1480
150 1620 1480 1320
200 1480 1350 1180
250 1350 1200 1050
300 1220 1080 920
12 50 2050 2050 2050
100 2050 2050 2050
150 2050 1920 1880
200 1180 1720 1150
250 1720 1580 1400
300 1550 1420 1220
1. For daylighting windows with a width-to-length ratio of less than 1:1.8, please refer to "Table B. Load Table of Plane PC Durable Plate with Fastening on Both Sides"
The thickness of the sheet in the table starts from 4mm, which is the minimum thickness that can ensure the permanent quality of the lighting window. Thinner plates can be suitable for placards, advertisements, vacuum forms, agronomic structures, temporary tents, etc.
Table B. Table of wind/snow loads. Conditions: flat, two-sided fastening, single-layer plate, single span.
Maximum recommended span between supports for daylighting windows with different aspect ratios under increasing wind/snow loads: Description: The previous general description of daylighting windows and the description of Table A are also applicable to this table.

Homogeneous load (kg/㎡)

Maximum support spacing (width of lighting window mm)
Type of thickness (mm)
4mm 5mm 6mm 8mm 10mm 12mm
50 780 980 1120 1800 1950 2050
80 680 820 1150 1680 1850 2050
100 620 700 1080 1550 1780 2020
120 580 620 980 1400 1700 1950
150 420 580 850 1180 1600 1780
200 Not applicable 420 650 1050 1480 1550
250 Not applicable Not applicable 450 950 1280 1350
300 Not applicable Not applicable Not applicable 820 1080 1200
General Load Table Notes:
① When the middle part of each span is subjected to the specified load, the PC solid plate table below is based on the generally accepted maximum deflection of the lighting window, which is 1/20 or 5% of the span. This ratio does not cause failure or damage to the daylighting window board in a short time, and the same applies to plastic daylighting windows. The span described in the table already includes the effect of the safety factor 1.7.
The high elasticity and extrusion characteristics of plastic make it produce a higher deflection ratio than other conventional building materials such as glass, but the deflection ratio will not cause any damage to the lighting window, and when the load disappears, the lighting window will return to its original position.
③ The high elasticity of plastic requires a larger notch and joint depth for the PC solid flat lighting window to ensure a reliable reserved position required for installation and prevent the lighting window from being separated from the original position due to improper deflection.
The higher thermal expansion rate of plastic requires a larger gap margin for the PC solid plate to ensure sufficient thermal expansion and prevent distortion and possible deformation.
⑤ Other lighting window installation details (clamping and fixing, sealing, etc.) are similar to the common methods of glass lighting windows, plus the special installation points of plastic materials mentioned elsewhere in this description.
⑥ The data in the table are based on professional skills, expert opinions, knowledge and experience, actual tests using sample lighting window panels, performance similar to other products, interpolation and estimation based on experience.
⑦ The PC solid plate form starts with a thickness of 4mm and uses this thickness as the minimum recommended thickness for a lighting window with permanent use quality. 1 to 3mm plates are suitable for signs, advertisements, vacuum form objects, agricultural structures, large tents for exhibitions, etc.
⑧ A PC solid plate can bear greater load before deformation, but inappropriate shortening caused by excessive deflection may be pulled out when the edge of the lighting window slides out of the load-bearing skeleton.
Additional internal supports, such as vertical supports or bow supports to the main rafters, can enhance the carrying capacity of snow loads when needed, but remain as they are when there are rising wind loads. Such a structure is suitable for heavy snow areas where the rising wind pressure is relatively moderate.
When making this selection, each item shall be calculated separately according to the relevant conditions.