Section 3 Web thickness to meet shear requirement
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Clasifications Register Guidance Information - Guidance Notes for the Classification of Special Service Craft – Calculation Procedures for Composite Construction, July 2013 - Chapter 5 Design of Stiffening Members - Section 3 Web thickness to meet shear requirement

Section 3 Web thickness to meet shear requirement

3.1 Ultimate shear stress from Table 3.1.2 Mechanical properties for woven roving (WR) and cross-plied (CP) glass reinforced polyester resin laminates at 0/90° degree orientation in Pt 8, Ch 3 of the Rules for Special Service Craft. From the web thickness (4,853 mm) given in Ch 5, 1 Calculation procedure 1.5 and the web laminate schedule given in Figure 5.1.3 Typical stiffener bonding arrange (i.e. total weight of 3650 g/m2) the effective glass content may be calculated, by transforming the relationship given in Pt 8, Ch 3,Pt 8, Ch 3, 1.2 General 1.2.6 of the Rules for Special Service Craft. The effective glass content of the web is therefore 0,47.

3.2 From Pt 8, Ch 7, Table 7.3.1 Limiting stress criteria for local loading of the Rules for Special Service Craft.

Limiting shear stress fraction = 0,33

Limiting shear stress = 0,33 x 76 = 25,08 N/mm2.

3.3 The shear stress requirement is given in Pt 8, Ch 3, 1 General of the Rules for Special Service Craft. By setting the shear stress to the limiting shear stress the equation may be rearranged:

3.4 The actual shear load is given in Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.2 of the Rules for Special Service Craft.

3.5 The shear stress coefficient is obtained from Table 3.1.5 Mechanical properties for woven roving (WR) and cross-plied (CP) aramid reinforced epoxy resin laminates at 0/90° degree orientation in Pt 8, Ch 3 of the Rules for Special Service Craft.

3.6 Consequently, the minimum web thickness to meet the Rule requirement is:

3.7 The actual web thickness is 4,853 mm. The deficiency is only 0,127 mm and is considered acceptable.

3.8 Finally, check the minimum Rule requirement for web thickness. From Pt 8, Ch 3, Pt 8, Ch 3, 1 General of the Rules for Special Service Craft.

3.9 For a web depth of 70mm and fibre content of 0,47 the minimum web thickness is 2,33 mm. Hence the minimum requirement is fulfilled.

Parent topic: Chapter 5 Design of Stiffening Members
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