Chapter 3

Question 1

List the 3 assumptions made when using c/c span

Answer 1

1) The reaction load is concentrated at the centerline of the support instead of being distributed over the width of the support.
2) The increase in stiffness at the support location is ignored. Beam is prismatic up to centerline
3) The beam is allowed to deflect up to the centerline, ignoring the presence of the column.

Question 2

List the 5 conditions in order to use AFA

Answer 2

1) There must be 2 or more spans
2) The loads must be uniform
3) factored live load must be less than twice factored dead load
4) The spans must not differ by more than longer span/shorter span <1.2
5) beam is prismatic

Question 3

What is the max shear load at center span

Answer 3

wlfL/8

Question 4

Why is Moment Redistribution done?

Answer 4

To account for the inelastic behaviour of concrete

redistribution can result in a lower number of bars being needed - more economical

Question 5

Recommended bar cut off

Answer 5

l/4 at end support

l/3 at interior support

Question 6

Describe direction of cracks. Which direction is of concern?

Answer 6

Cracks running parallel to flexural reinforcement are due to shrinkage and temperature effects.
Large cracks running perpendicular to flexural reinforcement are of concern - due to failure