Week 2 Challenge

1. Net Area for tension member calculation problem

Calculate the net section area for the tension member as shown in Figure below. The plate size is 260 x 20 thick and Bolt size is 20 mm.

Plate – Drilled Hole

Aim- To Calculate net section area of tension member of given figures.

Given data-

Plate width b= 260mm, thickness of plate t= 20mm, Bolt Size =20mm

Bolt hole dia dh =20+2 = 22 mm

As per IS-800.2007 Clause-6.3

Net area of cross section An = (b-n dh) t = (260 – 4 X 22) X 20 = 3440 mm2

Plate – Zigzag bolting

Angle (200 x 100 x 12 with M20 bolt)

Sip Steps:

• Refer Slide 26 for Net area calculation formula
• For angle section Flatten the member and calculate the gauge distance

2. Sag rod design problem

Design a sag rod as shown in Figure below. Purlins are supported at 1/3rd points by sag rods.

Assume centre to centre distance of Rafter spaced at 8 m , spacing of purlin = 1.2 m, Self weight of roofing (including thermal insulation)= 60 kg/m2 , Wind pressure intensity = 150 kg/m2,Slope of rafter = 15 degrees, Live Load =75 kg/m2. Assume self weight of purlin as 100 kg/m.

Tip Steps :

• Calculate total gravity load (DL & LL) on the purlin
• Calculate Wind load acting on the purlin. Note that wind load acts perpendicular to the member.
• Resolve and calculate the load acting parallel to the roof
• Force contribution to each sag rod is calculated
• Calculate required net area and chose a desired sag rod size.

3. Determine section size for given tensile load

Design a single angle member of length 5m to carry axial tensile force of 500 kN. Yield strength fy of the material to be considered is 350 N/mm2.

Tip Steps :

• Calculate required area of cross section from factored load
• Choose an angle section from required area calculated
• Calculate design strength of the member due to yielding
• Calculate design strength of member by tearing of net section
• For a given member assume bolts placed with appropriate edge/end/pitch/gauge distance and calculate block shear capacity
• Check slenderness is within limit