Bending Moment results for Beam Elements

[Arumugam ce19d044]

Dear All

Bending moment at the fixed ends of a Fixed-Fixed beam with beam element formulations is not matching with that of the results from the standard formula. It is a static analysis of a beam subjected to UDL load through *LOAD_BEAM_SET and with ELFORM = 1 & 4 in SECTION_BEAM. Please give guidance on obtaining convergence in the results.

Also need some guidance on using LS-DYNA for strength-assessment of existing structure that consists of reinforced sections of beams, columns, slabs and unreinforced masonry walls. 

Regards

Arumugam

[l...@schwer.net]

For your fixed-fixed beam end moments, I think you are missing the so called “work equivalent moments” at the ends in your model.

 

First consider a uniformly distributed load (UDL) on a simply supported beam. We know this beam will bend under the UDL. However, if we represent this by a single beam element we will have half the UDL acting at each end (node) directly over the end support – the beam will not bend.

 

What is missing are the end moments caused by the UDL, but not included in the simple vertical load only equivalent loading system.

 

Every discrete beam element should include these work equivalent moments. However, in a string of elements these moments typically cancel each other at the nodes of adjoining elements; for UDL case. Thus leaving only the moments at the end of the discretized beam.

 

Further, the magnitude of these work equivalent moments decreases with the length of the discretized beam element as the length squared:

 

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