Static tables of trapezoidal metal sheets

• ČSN EN 1990 (March 2004) Principles of designing of constructions
• ČSN EN 19931-3 (February 2008) Designing of steel constructions – basic rules and principles – complement rules for thin-walled cold-formed components and flat profiles

The tables are determining allowed area load for simple beams, for continuous beams of two simile fields and for continuous beams of three simile fields.

Values in rows 1a, 1b, eventually 1c are determining extreme projected load on the basis of entered support width, eventually overlap of simple beam over the support.

Values in rows 2a and 2b are defining characteristic load determined according on chosen bend limit.

This electronic version of tables is already taking into consideration the self-weight of metal sheets (values of allowed load in the tables are automatically lowered by this weight). Therefore it’s not necessary to consider the allowed self-load of the metal sheets.

Using of this electronic version of tables: After pressing “start calculations” you will be asked to fill in information about load and requested bend limits. It’s possible to enter final combinations of total load or use the „guide“ and enter the separate load factors and let the application generate final most favorable load combination automatically.

After entering the load and bend limits a recalculation is carried out, which changes the color of all cells in the table according to following rules:

	Use on less than 95%	- satisfactory with reserve
	Use on 95 - 100%	- narrow acceptable
	Use on 100-105%	- narrow unacceptable
	Use on more than 105%	- significantly unacceptable

For appropriate projection of the right sheet it is necessary to choose such a one, which is calculated as acceptable in all relevant fields.

Values of bearability are derived and valid only for the material S320GD and for cross-sections according to CB Profil standards and therefore can not be used for trapezoidal metal sheets of another producers.

Worked out for CB Profil a.s. by: Ing. Jan Seifert, Ing. Vítězslav Hapl and Doc.Ing. Tomáš Vraný CSc

ADDITIONAL NOTES

Notes to particular rows in the table are always mentioned under the corresponding table.

Technologické přitížení (rozvody apod.) se zadávají jako „Ostatní“ zatížení a to podle svého charakteru jako zatížení stálá nebo proměnná.

Row 2a is related to the bend limit for total load, row 2b to the limit of variable load. Unless there is no need for controlling of one of the bend limits (or both), it is enough to fill in the zero value of the limit.

Technological loads (weight of distribution systems etc.) are entered as “other” load and there according to its character as stable or variable.

Wind is considered only in that case, when having a pressure effect. When a “soak-up” effect of the wind is to examinated, it is necessary to make the right load combination with opposite marks (in order reach a positive value of the total load) and consider the fact, that weight of the sheet is already taken into account.

When using the GUIDE, the load combinations are made according to the articled Nr. 6.4.3.2 and 6.5.3 (2a) ČSN EN 1990. For “other” variable loads it is safely considered combination coefficient Ψ₀ of value 1.00. Partial safety coefficients of “load coefficient” are in comply with ČSN EN 1990 considered for constant load with value of 1.35 and for variable load with value of 1.50.

Potential hanging of lights, distribution systems etc. directly on the trapezoidal sheet are possible only under the condition, that final total load of each wave of the sheet will not exceed the total load considered in the static project. It is necessary to count with that fact, that the waves practivcally do not co-work and therefore can not help themselves with the load transfer. For approximate calculation of maximum total bear locally hanged on one wave it is possible to use following relation:

Pmax = qtech . b1 . l1 [kN]            kde	qtech [kN/m2]	is the area load from technologies (etc.) considered in the sheet projection
	b1 [m]	is standardized width of one sheet wave (for ex. 0,28 m for sheet CB 150/280/0,75)
	l1 [m]	is the distance between single hangings on one wave of trapezoidal metal sheet. The value l1 can not be higher than half of trapezoidal metal sheet span.

The hanging connection itself can not cause local weakening of the sheet and has to be projected to an appropriate load. We recommend using the standardized hangings from company CB PROFIL.

In case that the upper areas of supporting construction are not parallel with the trapezoidal sheet, it is necessary to fill the created wedges with appropriate material or complete the supporting construction with a formed metal edging that way, so the trapezoidal sheets will be laid on the supports with the whole area. Lying of the sheets just on the edge is not permissible. In case that the trapezoidal sheets won’t be laid along the whole support, it is necessary to consider this fact during the sheet projection. Minimum width of the support is 40 mm.

Potential spreads of trapezoidal sheets must be edged with changes and in the static projection a corresponding change of static scheme (for ex. Interruption of continuity of more-fields beam) must be considered. As well in this case it is not possible to count with co-working of the waves and each weakened wave has to staticly considered.

Definition of overlap of the sheet over the support for correct projection of the simple beam:

C	- overlap of inner edge of the support
hw	- sheet height