thiết kế nâng cao bê tông cốt thép (tiếng anh)

CE 5510 - 2004
Advanced Structural
Concrete Design
CE 5510 - 2004
Flat Slab System
• Column Heads
• Division of Panels
• Deflection
• Crack Control
• Shear
• Arrangement of Reinforcement
CE 5510 - 2004
Class Objectives
•Identify the types of slab construction, summarizing
the advantages and disadvantages of each
•Explain the methods of analysis of slabs
•Determine the design moments of one-way and two way
slabs
•Design of flat slabs covering:
division into strips, edge and corner columns,
punching shear and provision of shear
reinforcement
CE 5510 - 2004
Recommended Reading
• James G. MacGregor, “REINFORCED CONCRETE:
Mechanics and Design”, 3rd Ed., Prentice-Hall,
1997, Ch. 13 and 14.
• Allen, A. H., “REINFORCED CONCRETE DESIGN
TO BS8110 SIMPLY EXPLAINED”, E&FN Spon,
London 1988, Ch. 14
•The next few slides are from the Reinforced Concrete Council

CE 5510 - 2004
Types of slabs
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Flat Slab
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Analysis of Slabs
course
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One-way spanning slab
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Simplified
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Two way action – A rectangular panel
supported on all four side
• Curvature more severe along l
x
• Moment is short span higher
• Evaluation of moment is
complex as behaviour is
highly indeterminate
CE 5510 - 2004
Consider two strips AB and ED at mid-span.
Deflection at central point C is the same.
4
Deflection of udl beam =
5wl

384EI
=∆ kwl
4
CE 5510 - 2004
4
∆
AB
= k n
AB
l
y
4
∆
DE
= k n
DE
l
x
n
AB and
n
DE
are portions of total load intensity transferred to AB and
DE respectively.
Since ∆
AB
= ∆
DE
,
4

4
wl
wl
=
=
n
DE
4
y
4
n
AB
l
4
+
x
l
4
l
+
l
y x
y x
CE 5510 - 2004
n
DE
> n
AB
Shorter span strip, DE, supports heavier portion of load
and is subject to larger moment.

Assumption – supports are unyielding
If the supports of the single panel is flexible, e.g. beams,
columns, etc. the distribution of moment is more
complex.
Degree of stiffness of yielding support determines the
intensity of the steepness of the curvature contours in the
l
x
and l
y
direction and redistribution of moments.
CE 5510 - 2004
Two-way spanning slab
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CE 5510 - 2004
Mid Span
Moments
- corner supported
CE 5510 - 2004
Approximate
moment in
one direction
in slabs
supported on
columns at
corners
CE 5510 - 2004
Midspan
moment
-edge

supported
CE 5510 - 2004
Approximate
distribution of
moment in one
direction in
slabs with
symmetrical
supports on
four sides
CE 5510 - 2004
Moment
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Restrained Corners