Steel Buildings in Europe

Title APPENDIX D Worked Example: Design of portal frame using elastic analysis 41 of 44 4 - 122 8.3.1. Verification of spacing between intermediate restraints L m = 2 y t 2 pl,y 2 1 Ed z 235 756 1 57 , 4 1 38              f AI W C A N i EN 1993-1-1 Annex BB §BB.3.2.1 For simplicity, the purlin at mid-span of the haunched member is assumed to be aligned with the cross-section No. 3. Equally, the purlin at the end of the haunched member is assumed to be aligned with the cross-section No. 1.  = 661 471 = 0,71  1 C = 1,2 Appendix C of this document According to the Eurocode, the ratio t 2 pl AI W should be taken as the maximum value in the segment. In this case cross-sections No.1 and 3 have been considered, as shown in Table 6. Table 6 t 2 pl AI W ratio for cross-sections No.1 and 3 Cross- section (i) A (mm 2 ) I t (mm 4 )  10 4 W pl (mm 3 )  10 3 t 2 pl AI W 1 15045 81 4888 1961 3 12686 74 3168 1069 EN 1993-1-1 Annex BB §BB.3.2.1 For simplicity, in the calculation of I t and W pl , the middle flange has been neglected. The section properties of cross-section No.1 give the maximum ratio t 2 pl AI W . Therefore L m is calculated using the section properties of cross-section No.1. I z = 2168  10 4 mm 4 i z = A I z = 15045 10 2168 4  = 38 mm L m =   2 4 3 2 2 3 235 355 81 10 15045 10 4888 756 1, 2 1 15045 129 10 57 , 4 1 38 38                    L m = 700 mm Purlin spacing is 1345 mm  700 mm Therefore the design procedure taking advantage of the restraints to the tension flange given in Section C.2 of Appendix C cannot be used.