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[Rahul Ganguli29]

In a G+2 old building (more than 50/60 years old), we have to cover the bare roof by normal shed. I have already designed the shed using Tata Hollow Pipe members. Span length is 16.350 m. & the bay length (dimension of other side) is 19.05 m.
After design, the maximum reaction as per STAAD analysis is come almost near about 74 kN.The roof material is totally Lime concrete, therefore no typical RCC using Cement is absent there.
So, my concern is if I using chemical fasteners anchoring, what percentage of strength would be reduced in case of Lime concrete base instead of normal R.C.C.

Senior members of this Forum, please help me

[vikram.jeet]

Shed type roof str over old bldg with lime conc :

These are light wt structures but Wind loading is critical causing shed str to get uplifted due to wind pressures on roof . Also if shed  str is cladded  there is additional moment on supporting columns. All this need to be taken care.

In case of uplift of 7.4 tonne , since Lime conc str is old and not strong , it would be wise  to provide column anchors in form of fe 500  reinf bars , 2 nos  16mm dia right from floor level of 3rd I.e uppermost existing storey to be hooked into wall and concealed into plaster. This will ensure necessary Stabilizing weight against uplift of 7.4 tonne . But it cannot ensure resistance to any moment as result of cladding of shed. For that, stub columns with reinf bars ,at least 4 nos  required as per design of column having uplift tension force and moment from cladding.

If it is lean to roof shed , some moment from roof forces also contribute to be added to cladding moment. For A type shed unbalanced horz force from roof , though small can also be added.