STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

sidhaivam · SEFI Member Joined: 19 Sep 2014 Posts: 3

Dear Friends,

Need your experienced views/opinions/suggestions on the fwg problem
I present the problem stmt as under:-

1. Design an Octagonal Metal Roof with 1:15 pitch and central Crown.
2. Dimensions : sides of the Octagon = 9m
3. Height of the roof at Eaves =4.2m
4. RCC Circular Columns are at each apex of the octagon and are 900mmDia 5. Basic Wind Speed is 47m/s and Bldg is in EQ zone IV.
6. The walls of the Octagonal hall are in Brick masonary and have 18% Openings.
6. No columns are allowed in the octagon anywhere else.

This Bldg is in the ground floor and the floor below (UG) houses a larger Bldg. Now I have the following issues

1. For the wind loading external coeffs should I use the Table 6 and table 4 of IS 873-III( mono-sloped Roofs) or use Table 4 and Fig 2 of IS 875-III( Circular standing Conical Roofs).
2. What type of truss is well suited for this type of situation given the octagonal hips and common crown and the large column free space present.
3. Suggestions about the connection/member choice at the crown.

Thanks in advance in anticipation of your valuable views