3 posts in this topic
By Waqas Haider
Assalam o alaikum,
I am having a building with a semi circle shape. None of the footing is either parallel to global X-axis nor to the global Y-axis. The plan of footings is attached. The problem I am facing is, ETABS reports joint reactions along global X-axis and global Y-axis instead of along the local axes of column. Since my columns are at a degree to global axis, the joint reactions also becomes at a degree from column and footing. Since to use simple combined stress formula of
stress = P/A + Mx*Y/Ix + My*X/Iy
I need forces along axis of footing. Or i will have to resolve either moment of inertia of footing along direction of forces or vice versa, which is quite tough and time taking. The other option I can go for is to design footing in SAFE. But again here, there i dont find any option to rotate footing at a certain degree to match orientation of columns. If i rotate local axis of footing, It only rotates its local axes and meshing but not the footing physically itself. The orientation of footing remains same. How can i solve this problem? Either having reactions in etabs along local axes of columns can solve my issue so that i can design it manually or rotating footing in safe to match local axes of columns can solve my issue. So can any one guide me how to do either option? Thanks.
By kHURRAM ALI
aslamwalekum , when we design reinforced concrete elements , for beam we take 0.35 , for column and wall we take 0.7 and for slabs we take 0.25 as modifiers , but i read in aci that for servicibilty analysis these modifiers has to increase by 43% which means for beam it become 0.5 , for column and shear walls it become 1.0 and for slab it become 0.35 , by doing this model drift and deflection both reduce to almost half of its original value.
one thing more when we do manual check we dont take crack sections , for e.g for simply supported beam the deflection is 5\384 WL^4\EI , here the I (inertia ) is not the for the crack section ,its for the uncracked section , so what modifiers should be use 0.35 or 0.5 or 1.0
By groszni awesome
assalamualaikum sepakistan users
i wanna ask what are the considerations of using this ribraft foundation thing?
what are the advantages and disadvantages?
what are some load applied on it?
how do we design the slab and the beam?