Week 9 Challenge

Q1.

Aim: To design a 3 hinged pitched roof frame of a steel building.

Given data:

• The length of the column is considered as 10 m.
• The slope of the roof is 1 in 10 and the roof is accessible for maintenance purposes (75 kg/m²) only.
• Bay spacing is 5 m and the frame width is 20 m.
• Weight of roofing sheet = 5kg/m²
• Weight of purlins + tertiary members = 25 kg/m²

Solution:

Live load on the rafter= 75 x 5 = 375 kg/m=3.75 kN/m

Dead load on the rafter= (25+5) x 5=150 kg/m =1.5 kN/m

The calculated loads are applied on the model preapred in Staad Pro.

And a combination of DL+LL is created.

To simulate the internal hinge at the midpoint of the roof frame, In two connected members at the midpoint, release of Mx,My & Mz have been applied at the start and end node for corresponding members from specification tab.

Then, for design, AISC ASD has been chosen as design code and required parameters like ratio,Lx,Ly,Lz,Ky,Kz are assigned for different members as given below.

For starting, the section chosen for both and column was ISMB 300. But utilization ratio was on higher side. To get the value of utilization ratio, many iterations were done by considering different sections properties for the considered members. Finally, for ISWB 550 as section property for both beam and column, the utilization ratio is found to be less than 1.

Result:

The section for both rafter and column is found to be ISWB 550.

Q2.

Aim:To draw B.M.D for given frames.

Solution:

i)

(Loading diagram)

(Bending Moment Diagram)

ii)

(Loading Diagram)

(Bending Moment Diagram)

iii)

(Loading Diagram)

(Bending Moment Diagram)

Q3.

Aim: To determine the lateral deflection of all 3 cases of question 2.

Solution:

ISMB 600 has been chosen as the section property for all the members in the 3 cases.

i) Lateral deflection at point A-0.022 mm.

vertical deflection at B-0.767 mm

vertical deflection at C-0.022 mm

ii)Lateral deflection at A-209.926 mm

Vertical deflection at A-0.021 mm

Lateral deflection at B-210.168 mm

Vertical deflection at B-0.648 mm

iii)

Lateral deflection at A-15.278 mm

Vertical deflection at A-0.024 mm

Lateral deflection at B-15.261 mm

Vertical deflection at B-0.055 mm