johnson9883

bump

The part 2 has a length of 80mm , so total length of base = 40 +80 + 80 =160

No , what is com No , what is complemetary stress ? In the notes , why the I-beam is sheared in the direction outward and inward of the book ? it's not stated in the notes earlier in example , right ?

for this question , I'm having problem with the shear stress at point E and shear stress at centorid. normally , the shear stress at the centoid will be maximum , right ? But , in my working , I found that the shear stress at the centroid is smaller than the shear stress at E. What's wrong with the working ? i get y coordinates of centorid = 66.7mm For Ixx , i get (5.00x10^-5)(m^4) , For V(shear force ) , I use (437.5x10^3) For shear stress at centroid , i use formula of $$\tau = V(Q) / It $$ so at centroid , Q = (66.67x10^-3)(160x10^-3)(66.67x10^-3 / 2 ) = 3.56x10^-4 so $$\tau $$= (437.5x10^3)(3.56x10^-4) / (5.00x10^-5)(160x10^-3) = 1.9x 10^7 Pa at E , Q = Ay = (40x10^-3)(80x10^-3)(53.33x10^-3)**(2)** = 3.41x10^-4 so , $$\tau $$= (437.5x10^3)(3.41x10^-4) / (5.00x10^-5)(80x10^-3) = 3.6x 10^7 Pa For Q at E i have labelled it with the orange part , for Q at centroid , i have labelled it with the green part ....

why ? is it due to the case that the studiot post earlier ? the shear force act inside and outside of book on the beam ?

Do you mean that if the shear force is in this direction (green arrow to left and right ) , then my area of green part would be correct ? So, the shear force in the previous diagram you posted is inside and outside of the book ? it's not stated in the question whether the shear force is applied in which direction , how do you know the direction of shear force which is insdie and outside of book ?

why ? I dont understand ... for the green part , my working is the length of horizontal I-beam x (19.6mm) (122.22mm - (19.6/2) ) , But , unfortunealy , the length of horizontal I-beam is not given ..... I dont understand the author's working in notes , can you explain further ?

In the example , i suspect the selected A (area) is wrong... From the notes , A' is the area of top (or bottom ) portion of the member cross sectional area . But , in the example , we could see that the selected area is located to the right of the point where shear stress is calculated , is the notes wrong ? IMO , the selected A' should look like this , right ? (refer to green part in the 3rd photo )

In my book , it's stated that the at the boundary , the shear stress in beam = 0 . However , wheni tried the circled equation , i didnt get shear stress = 0 . What;s wrong with it ? Is the concept of at the boundary , the shear stress in beam = 0 . correct ? http://imgur.com/a/k9geD http://imgur.com/a/KKCGR