| 摘要 |
The upper chord of a metal roof truss which comprises an elongated beam (10) formed of rolled form metal strip which is of a constant cross-section having longitudinally extending portions (13, 14, 15 and 16) providing flat surfaces of such dimensions that with the application of excessive load upon the beam breakdown of substantially all of said portions occurs simultaneously, and wherein most of the flat surfaced portions are of a width not exceeding that which will comply with following formula (I), where: Fa = maximum permissible compression stress expressed in Mpa, OMEGA = load factor, Q = form factor which allows for the effective cross-sectional area, Foc = elastic buckling stress expressed in Mpa, Fy = yield stress expressed in Mpa. |
