I am using sap2000 program to model and analyze flat and beam slab systems. with different size and configuration of meshes in slab and wall elements I am getting different results. It would be very nice if anyone can share me a general guideline on meshing slab elemetns.
Thanks in advance!
Hello Ephrem and Qasim, it is obvious that the results should be different; it is mainly because of the size of the elements and the elements' approximate formulation and specifically shape functions. However, under the umbrella of convergence, all the approximate responses (results) can be considered acceptable and converging to the exact results, when the size of mesh converges to zero or when using higher order elements or their combination. Roughly speaking, a good mesh need to be denser in the areas of problem that the response changes faster and can be coarser when the response changes slower. The case is more complicated in nonlinear and nonlinear dynamic problems. However it seems out of the your question. OK, best wishes for you and all in the coming 2019.
Ephrem Beyene It is very natural that size of the mesh affects of the results.
To chose the best mesh size, must be calibrate your model with experimental results.
Generally, the best mesh size is equal to or less than the slab thickness.
Regards
Use auto-meshing options, or if necessary, mesh the slab manually. In manual meshing, you must be very careful in that:
1 - Number of elements, selected for each slab edge is such that the element shape is as near to the square shape as possible.
2 - There should be preferably even (multiples of 2) elements on each edge.
3 - You should have equal number of same width elements, in the length common to two adjacent slabs.
4 - End points of adjacent elements on both side of slab edge, perfectly match (VERY VERY IMPORTANT).
5 - Dimensions of mesh elements should be within the limits, prescribed by ETABS.
I personally like & recommend the second option, whenever there are a lot of warning messages.
REGARDS
Ephrem Beyene
In any FEM software you use, better to check the Manual (of the software) for the type of elements. In analysis of slab you need an element that considers the bending and the membrane stresses (to take care of the large deflection formulation if any). So, look for an element type that considers the large deflections of plates because it works for small and large deflections.
Regarding the mesh, better you do a convergence study to make sure the suitable mesh for each problem. In some problems there are sharp corners and opening where you need to refine the mesh to get an acceptable solution.
- Badges
- Science topic