The discussion revolves around the treatment of fixed end moments (FEM) in a structural analysis problem involving a beam with supports at points A, B, and C. Participants explore why certain fixed end moments are not considered in the analysis, particularly at points AB and BC, and how this relates to the classification of supports as pinned rather than fixed.
Participants generally agree that there are no fixed end moments at A, B, and C. However, there is disagreement and confusion regarding the specific values of fixed end moments and the implications of the support types on the analysis.
Participants express uncertainty about the assumptions made in the analysis, particularly regarding the classification of supports and the resulting fixed end moments. The discussion highlights the complexity of statically indeterminate beam analysis and the need for specific methods to address the problem.
One more problem , why (FEM)BC is 3PL / 16 ?PhanthomJay said:
You are correct that there are no fixed end moments at A, B, and C. But remember, these series of problems you have been working on are for statically indeterminate beams because there are more unknown external support reaction forces and moments than the number of equilibrium equations, so you have to resort to indeterminate analysis methods such as the slope-deflection approach or moment distribution method. These methods require you to assume initially that the interior joint (B) is fixed, then you release the joint from fixity and let the assumed FEM moment distribute to the other ends based on stiffness and carry over factors. In this example, in span BC, you temporarily fix joint B, and since the beam is pinned at C, you use the table for a fixed-pinned beam to get the FEM_BC of 3PL/16. After completing the analysis, you end up with only internal moments, but no external FEM moments at the supports.fonseh said:
