Permissible stresses in bending compression

Permissible stresses in bending compression Structural Steel Work 359 Section 8 S.ntlnn 8 Structural Steel Wo 358 8-22. MOMENT AND SHEAR CAPACITY OF BEAMS Section I Weight I Flange Web thick- Moment Shear

kg/m. thickness ness tw Capacity capacity

tf (mm) (mm) (ton-m) (ton) ISMB 100 11.5 7.2 4.0 0.85 4.0 150 14.9 7.6 4.5 1-.6 7.2 200 25.4 10.8 5.7 3.6 10.8 250 37.3 12.5 6.9 6.7 16.3 300 44.2 12.4 7.5 9.4 21.3 350 52.4 14.2 8.1 12.8 26.8 400 61.6 16.02 8.9 16.8 33.6 450 72.4 17.4 9.4 22.2 40.0 500 86.9 17.2 10.2 29.8 48.2 550 103.7 19.3 11.2 38.9 58.0 600 122.6 20.0 12.8 50.4 68.0 Unsupported

Effective

Length (m) MB600 MB500 MB400 MB300 MB200 MB 100 1.0 1650 1650 1650 1650 1650 1650 2.0 1650 1650 1650 1650 1650 1650 3.0 1650 1650 1526 1559 1382 1286 4.0 1650 1481 1120 1182 1003 1009 5.0 1376 1147 892 937 836 - 6.0 1104 886 759 801 730 - 7.0 885 770 665 707 - - 8.0 786 686 590 630 - - 9.0 703 611 - - - - 10.0 638 540 - - - - 11.0 573 - - - - - 12.0 527 - - - - - Note: In any case, ratio of effective length to least radius of gyration in any direction should not exceed 300 in case of bending members. Note: The moment capacity mentioned above is based on assumption ~ that full permissible bending stress is taken in calculation. However, ~ permissible bending stress in compression varies depending upon unsupported length in the lateral direction. This is because while the ; beam is bending in vertical direction (about X-X axis), it has also the' tendency to buckle laterally (about Y-Y axis). Hence, before beam fails in bending, it may fail by buckling in lateral direction. That is why in i actual calculation moment capacity will be calculated by seeing perm. Stresses in bending compression which will depend upon the unsupported length in lateral direction. They are given in the table below.

I. I