Hello so we will discuss how to calculate the design strength of a member.So I will go through one work out example through which we will try to see how to find outthe design strength due to gross yielding of the section, due to rupture of the critical sectionand due to block shear. So these three aspects will be seen in the workout example.And in the workout example we will go through one angle section in which one leg isconnected to the gusset plate that means the shear leg effect will come into picture.
Example:Two ISA 75×50×8 are connected to a gusset plate on its same side of thickness 10mm by fourM18 grade 4.6 bolts. Find the design tensile strength of the angle if (1) gusset is connected tothe longer leg (2) gusset is connected to the shorter leg.Solution:(1) Gusset connected to the longer leg2 ISA 75 × 50 × 8 connected back to back with its longer length.Thus, the gross area will be Ag = 2 × 938 = 1876 mm2
Let us assume pitch distance = 50 mm, edge distance = 30 mmThen we will go to calculation of the strength due to rupture of the critical section. So asdiameter is 18, so hole diameter will be dh diameter of hole become 18 + 2 that is 20 mm andwe can assume pitch distance as say 2.5d that is 50 mm and edge distance e as 1.5d that is 30mm, so we can use this, ok.
Here we have calculated the strength of the connection where the longer leg is connected.Now we will see what will be the design strength when the shorter leg is connected to gusset,this is one thing another thing we will see which one is efficient.
(2) Gusset connected to the shorter legStrength due to yielding of gross section:
Now if we compare that in case of first one the value is coming 426.36 kilonewton and incase of second one value is coming 390.86 kilonewton, right. And what we see here that iflonger length is connected then the strength is more strength of the joint is more. Sowhenever we are using unequal section we should try to join the longer length with the gussetplate to get the strength more with same material, right. So, this is how we can calculate thedesign strength of a member which is subjected to axial tension and the three criteria we willfollow and the least of these three will be the design strength of the member, thank you.
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