Video 1
Hello so today we will go through some worked out example. In last lecture, we havediscussed how to calculate the net area of a member along critical section. So the use of theformula, we will try today to find out the net area of the section for a given section
Example: Calculate the net area of an angle ISA 75×75×6 which is connected to the gussetplate through single leg as shown in following figure. Bolts used are M20 grade 4.6.
Example: A flat size of 200 × 8 mm of grade Fe 410 is used as tension member in a rooftruss. It is connected to a 12 mm gusset plate by M16 bolt of grade 4.6 using two alternatemethods of bolting as shown in following figures. Calculate the net area of the members.
Video 2
Example: A flat size of 200 × 8 mm of grade Fe 410 is used as tension member in a rooftruss. It is connected to a 12 mm gusset plate by M16 bolt of grade 4.6 using two alternatemethods of bolting as shown in following figures. Calculate the net area of the members.
(b) Zig-zag boltingIn this case, the critical section may fail along 1-2-3, 4-5-2-3, 4-5-2-6-7 or 4-5-6-7. Hence,the net area for all possible sections needs to be calculated and the minimum value will beconsidered as net area.
It may be noted that the section along 4-5-6-7 will not be critical as the strength of the bolt 1will be added to this section.Thus the net sectional area = min of (1456 mm2, 1537 mm2 and 1618 mm2) = 1456 mm2Therefore, the most critical sectional area will be along 1-2-3.So when we are we will be going for design of some connection we will try to prefer zig-zagbolting because it will be more efficient then the chain bolting. Now in next class we will discuss about the strength calculation of the tension member. Now tension member may faildue to yielding of the gross area so because of yielding what will be the design strength thatwe will be calculating.Next we will calculate the rupture of the critical section that means along critical section howit is going to fail that we will try to calculate and there we will see that shear leg effect willcome into picture and I told that shear leg happens when the hole sections are not connectedto the member. So, if part of the member is connected then the direct axial tension will firstcome to that portion and the shear leg effect will be there in the outstanding leg, which arenot connected.So, because of shear leg effect the strength is going to be reduced little bit. So we have tocalculate that shear leg effect and then we have to find out the design strength due to ruptureand another scope of failure will be the block shear failure as a hole it may fail due to shearwhich is called block shear failure.So for that also, we have to calculate how the block shear failure is going to happen and whatwill be the design strength and then out of this minimum of these three strength will be thedesign strength of the member.