some questions... (1 Viewer)

[CriminalCrab]

1. In I-beams, why is it structurally acceptable to cut holes into the web but not into the flange? Why are holes cut?
2. A galvanized steel post is anchored to concrete by zinc cobalt coated bolts. Why are the nuts on the bolts significantly more corroded?

3. Shear Force and Bending Moments: [multiple choice]
a) are equal to the reactions of a beam at the supports
b) are internal reactions to external forces applied along a
structural member
c) change along the length of the beam
d) are connected by the relationship that when the bending moment
is zero, the shear force will be a maximum.

4. A Uniformly Distributed Load (UDL): [multiple choice]
a) will produce the same shape Shear Force and Bending Moment
diagrams as several concentrated point loads placed along the
beam
b) can change in magnitude uniformly along the beam
c) has no effect on calculations on a simple beam
d) has the same magnitude acting at all points along the beam.

thanks in advance

 

[wingman]

Here's some hints.

1. Firstly, do you understand why I Beams are in the shape of an 'I'? When you've found the reason to its shape, you'll then understand why the amount of material at the centre of beam isn't critical (structurally). When you cut a hole out of the steel, what does it remove? Why would someone want to remove it?

2. http://www.galvanizeit.org/aga/abou...ng-does-hdg-last/in-contact-with-other-metals

3. Best to study the shear force and bending moment diagrams. They will help u eliminate the wrong answers.

4. Best to study the shear force and bending moment diagrams. They will help u eliminate the wrong answers.

Hopefully that's helpful.

Remember, Google is ur new friend

 

[CriminalCrab]

alright...
i'll use my brain...and giving it a go...
1. I-beams are I shaped because something about having more volume, hence strength in the top and bottom where the bending stresses are the greatest. So holes are cut to.....reduce material?. Structurally okay because....less stresses there?...not too sure.

2. zinc contact with another metal? the link you gave too complicated and i dont do chemistry...

3. to me, c and d seem correct

4. d and a sound the same....

so yea.... help?

 

[wingman]

1. Yep! you got it! reducing material is done to reduce weight and raw material costs.

2. I'm not 100% sure about zinc/cobalt corrosion combination, but reading how the question is asked, the answer would be Galvanic Corrosion. Here's a simple explanation of Glavanic Corrosion (http://www.corrosion-club.com/galvanic.htm)

3. Both c and d sound right, but going on the length of the answers (which usually is an indicator) it should be d.

4. Yep! d) has the same magnitude acting at all points along the beam.
It isnt a) because having concentrated point loads along the beam is not the same as same magnitude acting at all points (even though when we draw a UDL we have to use arrows drawn along the beam which seem it to be at concentrated points).

Hope that helped!

 

[CriminalCrab]

yay!!! thanks, it helped =)