Hello,
why seismosoft dosent support FEMA hinges? I know the fema links with the drop of strength can cause numerical problems in dynamic analysis but it is very ok for pushover. will seismosft do something for it?
Fema Hinge
Re: Fema Hinge
Hi mortezarazi.
I'm a little unsure of what you mean by a FEMA hinge, but I assume you mean plastic rotation capacities defining IO (immediate occupancy), LS (life safety), and CP (collapse prevention) limit states with their prescribed limits for steel or concrete frames in, for example, FEMA 356.
The way I interpret this is that the FEMA hinge method is less rigorous and based on more assumptions than the fiber-based approach available in SeismoStruct.
And FEMA 356, Article 2.4.3, states that "nothing in this standard shall be interpretted as preventing the use of any approved alternate analysis that is rational and based on fundamental principles of engineering mechanics and dynamics." I believe that the SeismoStruct methodology falls under this category.
Nonetheless, you may be able to mimic a FEMA hinge with some up front work to define the appropriate hinge properties in conjunction with either a plastic hinge inelastic force-based element or a trilinear link in SeismoStruct. And the SeismoStruct staff may very well see the need for the incorporation of FEMA-based hinges in SeismoStruct, which would be fine.
But I would say don't let the absence of such a feature hinder your use of results from the software.
I'm a little unsure of what you mean by a FEMA hinge, but I assume you mean plastic rotation capacities defining IO (immediate occupancy), LS (life safety), and CP (collapse prevention) limit states with their prescribed limits for steel or concrete frames in, for example, FEMA 356.
The way I interpret this is that the FEMA hinge method is less rigorous and based on more assumptions than the fiber-based approach available in SeismoStruct.
And FEMA 356, Article 2.4.3, states that "nothing in this standard shall be interpretted as preventing the use of any approved alternate analysis that is rational and based on fundamental principles of engineering mechanics and dynamics." I believe that the SeismoStruct methodology falls under this category.
Nonetheless, you may be able to mimic a FEMA hinge with some up front work to define the appropriate hinge properties in conjunction with either a plastic hinge inelastic force-based element or a trilinear link in SeismoStruct. And the SeismoStruct staff may very well see the need for the incorporation of FEMA-based hinges in SeismoStruct, which would be fine.
But I would say don't let the absence of such a feature hinder your use of results from the software.
Tim Huff
Re: Fema Hinge
yes as huffte said,fiber element is used in seismostruct and in this way,it is not really needed to defining moment-rotation base any code.Fema code procedure is just can be find in SAP2000,Etabs