I have tried plate load (which allows me to do nonuniform load) but it does't consider load with tributary area like floor load does, it seems to me "plate load" only distribute load to nodes not to the beam member. I am wondering is there a way to apply a CHANGING LOAD (load changes from one end to the other by a certain slope) in STAAD pro and at the same time CONSIDER TRIBUTARY AREA. I know both "surface load" and "plate load" allows you to do trapezoidal loads but they don't seem to give the right answer (or I could be wrong). As shown in the figure below, I applied 10kn/m2 load on the plate and the result on this beam is very different.
Plate loads are transferred to the adjacent elements or beams through the nodes. So if you define a single plate for the entire floor and apply pressure load on it, the load would directly be transferred to the columns without bothering the beams. You have to use a mesh of plates instead and the beams should be broken as well so that there is transfer of load at all of those common nodes. Then you can apply the varying pressure as a hydrostatic load applied on the plates.
If you want to avoid modeling the plates, the only way would be to directly calculate the varying load and apply these as member loads on the appropriate members using options like Trapezoidal or linear. A floor load cannot be used in this case as it would only allow applying a uniform pressure.
Answer Verified By: Joanna Zhang
Thank you very much Sir. I now understand how the load is being considered as a plate load.