Hi Everyone
When we analysis in Plaxis2d we see the results of model moment is kNm/m. we understand that the results are unit meter. Finally we multiply the results excavation step length in tunnel.
When we analyse same model in plaxis 3d, we see that the results of the model moment are also unit metre. Should we do so, multiply the results again by the excavation step length. Could you please help me
Burak,
By excavation step, I think you are referring to NATM tunnel and spacing of lattice girder, so that you can use the moment capacity contribution of lattice girder in tunnel. So, in that case, if you calculate your moment capacity for a beam supported with one lattice girder and shotcrete with a length equal to excavation length, it is correct that you multiply with excavation length. You can also use 1 m length, but in that case taking into contribution of lattice girder is harder, so excavation length makes sense. (Just see the previous reports in the company, I know you have it)
When you model in Plaxis 3D, you get the bending moments of every points seperately. For your purposes, you can take the maximum (or average, your decision) bending moment on the area of interest, and multiply that with excavation length. Or you can average the bending moment along a strip of excavation length.
Your question is not about Plaxis actually, it's about your moment capacity calculation. If you are calculating the bending moment capacity of a 1 m section as 150 kNm, 1.5 m section will have 150 x 1.5 = 225 kNm. You can multiply the Plaxis 3D results with 1.5 m in that case. It means you are analysing a beam with dimensions 1.5 m x t where t is your shotcrete thickness.
Good luck.
Answer Verified By: Burak Besli