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Special Moment frame Stair case

Gilbert Fontenard
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Good Day,

I am currently modelling a staircase supported by a moment frame and I have come across a strange occurrence. When I checked my column forces the axial forces seemed alright but the moments were strange as the moments generated along the top portion of my column is greater that that of the lower portions and supports, which seems incorrect based on the theory of bending moment. The model I generated employed the use of beam elements for my columns and beams and plate elements for my columns. I have included the Staad file for inspection. 

Thanks. STAIRS-frame.zip

  • 0 Offline in reply to Biswatosh
    If you select any column the observation is the same under all load cases. For example, let me use the column comprising members 576, 573 and 579, and lets investigate case number 1: EQ +X (+ACC). If you notice member 579 (Which is located at the top of the structure) has the largest moments (Mz =8.87,-10.9), while member 573 (Mz =-0.254, -2.34) and member 576 (Mz = 3.99, -3.25) have smaller moments despite being closer to the base of the structure, which seems highly inaccurate.
  • 0 Offline in reply to Gilbert Fontenard

    Hello Gilbert Fontenard,

    Sir I have downloaded your STAAD file in order to review your Error but sir I did not find any inaccuracy in the STAAD report as it may be the case after  final moment distribution of the various members, its not necessary that the top column has to have lower moments then the bottom column rather top column will have less axial force than the bottom column.

    I have attached a pdf file in order to give a clear indication of the moments distribution method please view it and let me know if it has solved your query.

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