C Purlin Design Excel Sheet

C Purlins

C purlins are commonly used in roofing and sheeting structures in steel framed buildings. This commonly includes steel frame warehouses, agricultural and industrial buildings. Steel framed buildings are also commonly used in high rise residential and office buildings also.

C purlins most common application is as roofing and sheeting rails. The C purlins fix to the main steelwork and span the gaps, allowing roofing panels and exterior cladding sheets to be fixed to the purlins. This provides stiffness and strength to the roofing and cladding without the sheets having to span between the main columns and steel beams.

C purlins are suitable due to their unique shape. The C shape allows the purlins to be easily fixed to the main steel work and to the roofing or exterior cladding sheets. Small returns or lips on the ends of the flanges stiffen the section making even very thin steel C purlins strong enough to span large distances between columns.

C Purlin Design Procedure

The CivilWeb C Purlin Design XLS allows the designer to complete the design of a C purlin in minutes with a few simple inputs. Firstly the designer must enter the geometrical information for the proposed C purlin. The spreadsheet allows the user to analyse a lipped C purlin of any dimensions including asymmetrical stiffening lips or flange widths. The designer must also enter the effective width in both axes and a restraint factor which is taken from a table in BS 5950. For ease of use this table is reproduced in the spreadsheet for guidance.

The final step is for the designer to input the loadings which the C purlin will be designed to resist. These forces include axial compression, shear forces and bending moments about either axis. The designer can also enter bending moments at max shear and shear forces at max moment which allow the spreadsheet to analyse the combined effects of bending and shear forces on the C purlin.

After these simple inputs have been entered, the CivilWeb C Purlin Design Spreadsheet can complete the analysis calculations in accordance with BS 5950-5. These calculations include;

• Calculation of the effective section properties including effective area, second moment of area for X, Y and neutral axes, local buckling coefficients, effective width and modified compressive design strengths
• The spreadsheet checks the section is sufficiently stiff
• Flexural Buckling Under Axial Compression Loads
• Major Axis Moment Capacity Check
• Minor Axis Moment Capacity Check
• Shear Resistance of the Web Check
• Combined Bending and Shear Resistance Check
• Combined Bending and Compression Check

The CivilWeb C Purlin Design Spreadsheet includes unique design features which show the user the effects of any changes to the effective length of the C purlin. The designer can use this to modify the effective length to suit the C  purlin capacity.

The spreadsheet completes all the calculations instantly, every time any alteration is made to the inputs. The spreadsheet presents the results of the calculations using a utilisation factor which shows the designer exactly how mush of the capacity of the section is being used. This also allows the designer to see whether the C purlin design can be optimised. The results are also presented to the user in red or green depending on whether the C purlin is adequate or not.

CivilWeb C Purlin Design Excel Sheet

The CivilWeb C Purlin Design Excel Sheet is an advanced spreadsheet for the design of C purlins. The spreadsheet is capable of analysing C purlins of any dimensions, either standard or non-standard. The calculations are completed instantly in accordance with BS 5950-5, allowing the designer to complete an optimised C purlin design in minutes.

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