# Homework Help: HW verification and question - One-way concrete slab reinforcement problem

1. Mar 11, 2009

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HW verification and question -- One-way concrete slab reinforcement problem

1. The problem statement, all variables and given/known data

A rich developer has convinced you to design a suites hotel in a mixture of French Chateau and Colonial Revivalism.

The basic structure is to be comprised of a continuous oneway slab supported by concrete walls between rooms. The maximum spacing of the walls is to be 5m. The loading is to be as follows:

Live Load: 1.9 kPa

Dead Load: self-weight of slab – note that concrete is 23.5 kN/m3

1) Determine the minimum thickness (hmin) of the slab (round up to
the nearest 10mm) based on the thickness requirements provided
in the course notes. (

2) Determine the typical reinforcing required for both positive
bending moment (bottom bars) in the span and negative bending
moment (top bars) over the supports. For a continuous system,
the positive moment is Mf=wfL2/16 while the negative moment
over the support is Mf=wfL2/11. The minimum bar size to be used
is 10M for bottom bars and 15M for top bars. The maximum
spacing of reinforcing is 500mm. Cover is to be taken as 20mm.
f’c=30MPa.

2. Relevant equations

positive moment is Mf=wfL2/16

negative moment
over the support is Mf=wfL2/11.

3. The attempt at a solution

1) Minimum thickness of the slab (one-way continuous) = L/24 = 5000 mm / 24 = 210mm

(derived using the following equation from course handout)

(Clause 9.8.2.1 of CSA A23.3 provides minimum thicknesses for one-way construction that are useful for preliminary sizing of one-way systems in order to estimate self-weight for design purposes)

(Solid one-way slabs)
simply supported = L/20
One end continuous = L/24 <---------------------- I used this one.
Both ends continuous = L/28
cantilever = L/10

(Beams or ribbed one-way slabs)
simply supported = L/16
One end continuous = L/18
Both ends continuous = L/21
cantilever = L/8

2) see attached images.

page 1 -- http://farm4.static.flickr.com/3643/3347943836_96b598f895_b.jpg

page 2 -- http://farm4.static.flickr.com/3448/3347941934_ff9265f7c4_b.jpg

page 3 -- http://farm4.static.flickr.com/3643/3347943836_96b598f895_b.jpg
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution