Steel desig calculation Mry

[Anonymous]

Hi,

Maybe the calculation of Mry it’s not good, please see in attachment my hand calculation and substructure file

Thanks

[Anonymous]

Could someone of support team see my first post to dertemine if the calculation of Mry in Robot is wrong ? I appreciate an answer as soon as possible because is urgent

[Artur.Kosakowski · Accepted solution]

The initial investigation indicates that for I sections with flanges of class 4 and webs of class 3 and lower the value of Mry is too low. The reason seems to be in taking value of Fy (350 MPa) in the incorrect units (kN/m2 instead of MPa) which results in the incorrect value of be = 2 * 200*t/sqrt(Fy).

The workaround (if acceptable) I can thin of is to reduce the steel resistance (e.g. to 340 MPa ?) so that the section doesn't fall into the above category (you may then consider slight increase in the limit of the verification ratio).

In addition I think that in your hand calculations the value of Mry is wrong due to the 'missing' 2 in the be formula as the I section has the 'flange' on both 'sides' of the web.

[Artur.Kosakowski]

The initial investigation indicates that for I sections with flanges of class 4 and webs of class 3 and lower the value of Mry is too low. The reason seems to be in taking value of Fy (350 MPa) in the incorrect units (kN/m2 instead of MPa) which results in the incorrect value of be = 2 * 200*t/sqrt(Fy).

Corrected in SP3 for Robot 2015.