Analysis Aid Preparation for Self Supporting Fixed Ended Helical Stairs
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Date
2015
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Abstract
As amazing its appearance is, spiral stair has complex geometric configuration. As a result of
this complexity, its analysis is challenging. And our Building Code of Standard doesn’t have
analysis aid for these special structures, like the ones we have for slabs. Hence, the purpose of
this study is to come up with a convenient and user friendly analysis tables and charts for the
analysis of spiral stairs. This research follows analytical and finite element approach
interdependently. The out come of the research is perceived by accompanying the comparative
assessment of the two approaches.
The analysis of spiral stairs is done in different approaches. First detail formulation is derived
for the stair using strain energy concept considering the stair as twisting girder and in plane
curved beam. Secondly, modeling and analysis is carried out using finite element technique as
3D twisting beam and 3D twisting shell stair slab separately. Then, graphical and tabular
comparison is done between all approaches. In addition, modification factors are formulated
considering variation of internal actions along stair width. More over, valid width is demarcated
to limit the acceptable width for the applicability of centerline model for stain energy solution
of helical stairs.
Hence, the analysis tables and charts that are annexed in the write up together with the
modification factors presented are very crucial tools for the analysis of these spectacular
complex structures.
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Structures