Material nonlinearity

[Shz713]

To consider only material nonlinearity in SAP2000:

-what would be the mass source for subsequent load cases after nonlinear dead load as initial case? Two options are available, default mass source and from previous load case.

-how to find the point in which materials enters plastic state and no longer elastic? Is any plot or data produced after analysis?

Cheers,

Shoot for the Moon, even if U miss, U still land among Stars!

 

[precast123]

Plot Stress vs Time. At some point of time stress will become constant indicating material has entered plastic state.

 

[Shz713]

Thanks for your input. In case of shell elements, what stress I need to plot against time using time history analysis? How about frame elements? To plot any value against time, then the required load case must be in dynamic state to be able to plot the stress/force vs time.

Shoot for the Moon, even if U miss, U still land among Stars!

 

[precast123]

What material non linearity you are using? Yes you have to perform time history analysis. See the attachment. Its the plot for a pipe which is axially loaded. At some point of time, the stresses becomes constant.The pipe material is High density polyethylene.

You can plot Von Mises stress.

 

[Shz713]

Most likely I'd use reinforced cocnrete with user-defined stress-strain curves. I reckon for shell and frame elements depending on the pattern of loading, different stresses vs time could be plotted other than Von Mises stress. Have you tried to plot other stresses? Currently I don't have access to SAP2K.

Shoot for the Moon, even if U miss, U still land among Stars!

 

[precast123]

I have used Abaqus for non linear dynamic analysis. For a frame member you can get results of Bending moment and manually calculate bending stresses(M/I * y) and plot them against time. I have always worked with Von Mises stress. Dint tried others.

 

[Shz713]

I reckon depends on purpose of analysis and nature of loading, various plots could b made. Since we're dealing with NL of structure, then it'd be better if stress is illustrated versus time to study at which instant the structure enters plastic state.

Shoot for the Moon, even if U miss, U still land among Stars!