In addition I also used a bigger section than the default W18x35 and the moments were amplified. I then used a general section I created with most properties set equal to 1 including the depth and the results matched the MD results. As you can see the ration of span to depth is well below 10 and the moments were alot bigger than the moment distribution results. My model involved 24in spans with the default W18x35 section. Hidden at the very back of the text was one page which states that whenever your span to section depth ratio exceeds 10 the effects of shear deformation are negligible and when that ratio is below 10 then the effects become considerable. A multi-story, multi-bay framed structure was then used to illustrate the efficiency of the moment distribution method with EXCEL. In this paper, a 3-span continuous beam was used to demonstrate the moment distribution method using EXCEL. I have a matrix analysis book by Kassimali and throughtout the book shear deformations are ignored in the calculation of the stiffness matrices. 3-span continuous steel beam subjected to uniform loads and self weight. It was the shear deformations that were causing such dramatic changes in the results.
Thank you very much for all your comments. for a span with one end pinned, the fixed end moment (at the rigid end). In the moment distribution method, initially. I am puzzled, any helpful tips? RE: Moment Distribution Discrepancy aggman (Structural) 19 Apr 05 14:15 Doing it this way should be consistent with the way you calculate fixed end moments, i.e. It can be described as a method which gives solution by successive approximations of slope defl ection equations. The moments calculated using the moment distribution method for the first interior support are significantly lower than the SAP results. At the end of this course you will learn to successfully analyse indeterminate structures, understand concept of static and kinematic indeterminacy, fixed end moments for various conditions and draw bending moment diagrams for indeterminate structures. It seems the more spans the further off the results get for the spans adjacent to the cantilevers. A shortcut one step moment distribution method is shown in this section. The examples were all two or three span continuous and the results matched fine. 3-span continuous steel beam subjected to uniform loads and self weight. At first I thought I was making an error in the inputs for SAP so I checked moment distribution examples from my text book versus results produced by SAP. I have had three other fellow engineers check the hand calcs to see if any errors were made in calculating K's, DF's, the use of the COF's and for random sign errors, no errors were found.
The hand method I am most familiar with is moment distribution and the results are not matching within a reasonable percentage for the spans closest to the cantilevered ends.
The models consist of twenty equal spans with cantilever end spans and a uniform load across the entire beam. I have been running continuous beam models in SAP2000 and trying to verify those results using hand calculations.
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