Thursday, March 13, 2008

Mixing Concrete and Concrete Beams - Day 2 - Questions

1. A simply supported reinforced concrete beam spans 22 ft as shown. The beam is subjected to a uniform service dead load equal to 2.1 kips/ft (exclusive of beam weight) and to a uniform service live load of 2.5 kips/ft. f’c = 3000 lbf/in^2 and fy = 40,000 lbf/in^2. The depth of reinforcing is 25 in

a) Find the factored uniform load.
b) Find the tension steel required for the maximum moment
c) Find the maximum area of tension steel permitted
d) Find the minimum area of tension steel permitted
e) Find the maximum uniform factored load that the beam can sustain if no compression steel is used
f) Find the spacing of No. 3 U-shaped stirrups at the location where the shear is maximum
g) Find the total length of the beam where no shear reinforcement is required
h) Find the maximum uniform factored load that the beam can be designed for.
i) If live load is reduced to 50% of maximum, what is the new service moment
j) Find the cracking moment

2. A reinforced concrete T beam with a 25 ft span and a 24 in effective width in a floor slab system is fixed at both ends and is reinforced as shown. f’c=3000lbf/in^2 and fy=60,000lbf/in^2
a) Find the design moment capacity in the positive moment region
b) At capacity – find the stress in the compression steel in the negative moment region
c) Find the gross moment of inertia
d) Find the cracked moment of inertia in the positive moment region
e) Find the cracking moment in the positive moment region
f) Find the cracking moment in the negative moment region
g) If a uniformly distributed service load of 3.5 kips/ft acts on the beam. Using refined equation for steel stress, find the stress in the tension steel in the positive moment region.
h) Find the maximum spacing of the tension steel bars based on cracking
i) Find the maximum uniform factored load that the beam can sustain as controlled by shear reinforcement
j) Find the maximum uniform factored load that the beam can sustain as governed by the flexural capacity.

3. A beam must withstand and ultimate factored moment of 410,000 ft-lbf. f’c=4000 psi and fy=40,000psi. No 3 stirrups will be used. (Do not design shear reinforcement, check for cracking or deflections)

a) Determine beam width and depth
b) Determine required steel area
c) How many layers of steel are needed?
d) what is the overall beam depth?

4. The simply supported tension-reinforced beam shown carries 2 identical sets of point loads and a set of uniform loadings. The beam has a width of 18 in. f’c= 3000psi, and fy=60,000psi.
a) Find the ultimate moment
b) Find minimum reinforcement depth
c) Detail reinforcing steel
d) Use No 3 bars to design shear reinforcing

3 comments:

Thiruppathy Raja said...

What an exciting experience!/Hilarious! Delightful! True!/wonderful stuff! thank you!
Retaining Walls

Unknown said...

Hi! nice post. Thank you for sharing. Cheers!

- The mixing packaging

Micheal Alexander said...

Interesting Article. Hoping that you will continue posting an article having a useful information. Beam design