CSA A23.3-04 Changes

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Nov 26, 2013 (3 years and 10 months ago)

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CSA A23.3
-
04 Changes


NBCC load & combination factors



c

changes from 0.6 to 0.65


Clause 8


load and combination to appendix


Clause 10


small changes to slenderness


Clause 11


major changes


Clause 13


slab bands


Clause 14


major re
-
write


Clause 15


piles and pile caps added


Clause 21


major changes


Clause 23


minor changes


Append D


anchorage is all new

Clause 10 Flexure and Axial Loads

)
2004
(
1
4
.
0
)
1994
(
25
.
0
)
2004
&
1994
(
1
2
.
0
d
g
c
g
c
d
st
s
g
c
I
E
EI
I
E
EI
I
E
I
E
EI









The old simplified equation for
effective moment of inertia has been
changed.

Clause 11 Shear and Torsion


This Clause has major changes.


The simplified and general method
approach is gone, there is now only one.


The cases previously covered by the
simplified method are now special cases.


The general method has been changed and
the tables are gone replaced by equations.

Clause 11 Shear and Torsion

94
3
.
23
2
.
0
'


A
d
b
f
V
w
c
c
c

04
3
.
23
72
.
0
9
.
0
'



A
h
or
d
d
d
b
f
V
v
v
w
c
c
c


04
3
.
23
cot
94
3
.
23




A
s
d
f
A
V
A
s
d
f
A
V
v
y
v
s
s
y
v
s
s



Clause 11 Shear and Torsion

11.3.6.2

Values for Special Member Types


Unless permitted otherwise by Clause

11.3.6.3 or Clause

11.3.6.4,
the value of β shall be taken as 0.21 and θ shall be taken as 42
°

for
any of the following member types

(a)

slabs or footings with an overall thickness not greater than 350

mm;

(b)footings in which the distance from the point of zero shear to the
face of the column, pedestal or wall is less than 3 times the
effective shear depth of the footing;

(c)

beams with an overall thickness not greater than 250

mm;

(d)concrete joist construction defined by Clause

10.4; and

(e)

beams cast integrally with slabs where the depth of the beam below
the slab is not greater than one
-
half the width of web nor 350

mm.

d
b
f
d
b
f
d
b
f
V
w
c
w
c
v
w
c
c
c
'
'
'
1134
.
9
.
21
.
6
.







Clause 11 Shear and Torsion

11.3.6.3

Simplified Method


In lieu of more accurate calculations in accordance with
Clause

11.3.6.4, and provided that the specified yield strength
of the longitudinal steel reinforcement does not exceed
400

MPa and the specified concrete strength does not exceed
60

MPa, θ shall be taken as 35
°

and β shall be determined as
follows

(a)

If the section contains at least minimum transverse
reinforcement as required by Equation

(11
-
1) then β shall be
taken as 0.18;

d
b
f
d
b
f
V
w
c
v
w
c
c
c
'
'
1053
.
0
9
.
0
18
.
0



s
d
f
A
s
d
f
A
s
d
f
A
V
y
v
s
y
v
s
v
y
v
s
s








29
.
1
43
.
1
9
.
0
cot
Clause 11 Shear and Torsion

(b)
If the section contains no transverse reinforcement and the specified
nominal maximum size of coarse aggregate is not less than 20

mm
then





(c)
Alternatively, the value of b for sections containing no transverse
reinforcement may be determined for all aggregate sizes by
replacing the parameter dv in Equation

(11
-
9) by the equivalent
crack spacing parameter sze where






however sze shall not be taken less than 0.85sz. The crack spacing
parameter, sz, shall be taken as dv or as the maximum distance
between layers of distributed longitudinal reinforcement, whichever
is less. Each layer of such reinforcement shall have an area at least
equal to 0.003bwsz, see Fig.

11
-
2.


)
9
11
(
169
.
0
400
)
(1000
230







then
d
if
d
v
g
z
ze
a
15
s
35
s


Clause 11 Shear and Torsion

11.3.6.4

General Method

The values of β and θ shall be determined from the
following equations



)
s
1000
(
1300
)
1500
(1
40
.
0
ze
x






x
7000
29




)
A
2(E
5
.
0
/
s
s
p
p
po
p
f
p
f
v
f
x
A
E
f
A
N
V
V
d
M







Clause 13 Two
-
way Slab Systems



Major change
-

added slab bands


Narrowed the ranges of distribution to
negative and positive steel in the column
strips

Clause 13 Two
-
way Slab Systems


Now have four categories:


Slabs
-
0.70 to 0.90 and + 0.55 to 0.65


Drop Panels
-
0.75 to 0.90 and + 0.55 to 0.65


Slab Bands
-
0.80 to 0.90 and + 0.80 to 1.0


Slabs on Bands
-
0.05 to 0.15 within b
b
and rest uniformly
distributed across entire width (including b
b
)


positive moment at all spans where



0.50 to 0.60


positive moment at all spans where









to




0
.
1
2
1





0
.
1
2
1





2
1
5
.
0




2
1
6
.
0


Clause 13 Two
-
way Slab Systems



Slab Shear


size effect for two way (punching) shear


no more principle axis calculations


One
-
Way shear on revised perimeter for corner columns,
just d/2 away from column and if column is in from the slab
edge maximum of d beyond


Edge loads
-

minimum top steel between columns


Finite element analysis


Revised relations to deal with
m
xy


)
1000
/(
1300
d

Clause 14 Walls


Complete re
-
write to address the wider range of walls being
designed.


Three basic categories


Bearing walls


Non
-
bearing walls


Shear walls


Covers many general requirements such as:


lateral support


concentrated loads


vertical loads through floors and shear across construction
joints


Clause 14 Walls


Wall



vertical slab element, which may or may not be
required to carry superimposed in
-
plane loads, in which the
horizontal length,
ℓw
, is at least 6 times the thickness, t, and
at least 1/3 of the clear height of the element.


Bearing Wall



a wall that supports

a.
Factored in plane vertical loads exceeding 0.1 f
c
’A
g

b.
weak axis moments about a horizontal axis in the plane
of the wall

c.
Shear forces necessary to equilibrate the forces in (b)

Clause 14 Walls


Non
-
bearing Wall



a wall that supports f
actored in plane
vertical loads less than or equal to 0.1 f
c
’A
g

and, in some
cases, moments about a horizontal axis in the plane of the
wall and the shear forces necessary to equilibrate those
moments.


Shear wall


a wall or an assembly of interconnected walls
considered to be part of the lateral
-
load
-
resisting system for a
building or structure. Shear walls support

a.
Vertical loads

b.
Moments about horizontal axes perpendicular to the wall
(strong axes bending)

c.
Shear forces acting parallel to the plane of the wall


Clause 14 Walls

14.1.8.7

Ties for Distributed Vertical
Compression Reinforcement.


Distributed vertical reinforcement, if
stressed in
compression
, shall be tied and detailed in
accordance with the provisions for column
reinforcement in Clause

7, except that ties can be
omitted if:

a)
the area of vertical steel is less than 0.005Ag,
and

b)
the bar size is 20M or smaller.

Clause 15 Foundations


Extensively revised to add new treatment of
piles and pile caps.


For example provides reductions for
effective cross section and capacity for
uncased piles.


Requires design for the range of specified
tolerance with a minimum of
±

50 mm


Clause 21 Seismic design


A general revision to align with NBCC
changes such as the introduction of R
d

and R
0

as well as new drift limits.


Enumeration of code recognized ductile
systems


NBCC Concrete Ductile Systems

SINGLE WALL
Rd = 2.0
Rd = 4.0
COUPLED WALL
Rd = 2.5
MOMENT FRAME
Rd = 3.5
Rd = 4.0
Rd = 3.5
Plastic Hinges to Absorb Energy

Example Unclassified Systems



OUTRIGGER WALL
FRAME WALL
WALL - COLUMNS
BRACED FRAME
Clause 21 Seismic design


Removal of limit of 55 MPa on f

c
.


Revised (revised from CPCA Handbook
values) effective stiffness factors for wall
and coupling beams to be used for analysis.


New relations for transverse reinforcement
for R
d

= 4.0 columns including the effect of
axial load level.


Clause 21 Seismic design

21.2.1.2


For the purposes of determining forces in and deflections of the structure,
reduced section properties shall be used. Table

21
-
1 lists the effective
property to be used as a fraction of the gross section property.





Table

21
-
1



Element Type

Effective Property

Beam

Ie = 0.4 Ig

Column

Ie =

c

Ig

Clause

21.6.8.6 Coupling Beam

Ave = 0.15Ag ; Ie = 0.4Ig

Clause

21.6.8.7 Coupling Beam

Ave = 0.45Ag ; Ie =0.25 Ig

Wall

Axe =

w

Ag ; Ie =

w
Ig

Slab Frame Element

Ie = 0.2 Ig

Clause 21 Seismic design


Column and wall stiffness reduction factors

0
.
1
6
.
0
5
.
0
'



g
c
s
c
A
f
P

0
.
1
6
.
0
'



g
c
s
w
A
f
P

Column Confinement (Cl. 21.4.4.2)



c
yh
c
ch
g
f
sh
sh
f
f
A
A
P
P
n
n
A
'
0
2
2
.
0




n
l
= 4
n
l
= 8
Clause 21 Changes


Ductile Walls


Clarification of when a wall with openings may be
treated as a solid wall


Revised requirements for the extent of ductile
detailing over the building height


Added tying requirements for distributed
reinforcement in ductile walls reflecting changes
to Clause 14.


Clarified the minimum concentrated reinforcement
requirements for flanged walls


Explicitly named “buckling prevention” ties

20

Plastic Buckling + Tension Yield

Clause 21 Seismic design


Revised relations for wall ductility that
include consideration of the effects of
height to width ratio and design
displacement on ductility demand.


Relations framed in terms of wall rotational
demand and wall rotational capacity.


Requirement to check rotational demand
and rotational capacity of coupling beams.

Clause 21 Changes


Ductile Walls


Introduced a “ductility” limit state for
plastic hinges in walls and coupling beams


Rotational capacity
≥ Rotational demand





Added requirement to check rotational demand
and rotational capacity of coupling beams


id
ic



Rotational Demand (Cl. 21.6.7.2)



w
w
f
d
o
f
w
w
f
d
o
f
id
Δ
nt
Displaceme
Elastic
R
R
Δ
nt
Displaceme
Design
h
Δ
R
R
Δ















004
.
0
2


id

f(RdRo -

w)
hw
hw - Lw/2
Lw
Lw/2
Rotational Capacity (Cl. 21.6.7.3)

Ultimate Curvature
Esy=0.002

ic =
L
p
(

u -

y
)
Yield Curvature
Es max = 0.05
Ecy=0.002
Ecu=0.0035
C






























w
s
w
ic
w
cy
sy
cu
w
ic
w
w
cu
ic
c
Length
Hinge
Plastic
c






max
max
2
2
2
025
.
0
002
.
0
2








Coupled Walls

21.6.8.2


The inelastic rotational demand on Ductile
Coupled and Partially Coupled Walls shall
be taken as:










where



is the total Design
Displacement.

d
o
f
R
R
Δ
004
.
0



w
d
o
f
id
h
R
R

Coupled Walls

Coupling Beams

21.6.8.4


The inelastic rotational demand on coupling beams shall
be taken as:




The inelastic rotational capacity of coupling beams

ic
shall be taken as:


(a)

0.04 for coupling beams designed with diagonal
reinforcement in accordance with Clause

21.6.8.7 and


(b)

0.02 for coupling beams designed in accordance
with Clause

21.6.8.6.

u
cg
w
d
f
id
h
R
R












0

Pin Ended Coupling Beam

Pin Ended Example

Pin Ended Case (Cl. 21.6.8.9)

Pin Ended Case (Cl. 21.6.8.9)

21.6.8.9


If the wall at one end of the coupling beam has a
factored resistance less than the nominal coupling
beam resistance, the following requirements shall
be satisfied:

(a) the coupling beam shall satisfy the shear stress
limitations of Clause

21.6.8.5 and the
requirements of Clause

21.6.8.6

(b) the wall shall be designed to the requirements of
Clauses

21.4.4.1 to

21.4.4.3, Clauses

21.4.4.6
and

21.4.5

(c) the joint between the wall and the coupling beam
shall satisfy Clause

21.5.

Torsion on Tubes

Torsion on Tubes

21.6.8.12


Assemblies of Coupled and Partially Coupled Shear Walls
connected together by coupling beams which function as a closed
tube or tubes shall be designed with:

(a)

that portion of the overturning moment due to lateral loads resisted
by axial forces in the walls, increased at each level by the ratio of
the sum of the nominal capacities of coupling beams to the sum of
the factored forces in the coupling beams required to resist lateral
loads above the level under consideration

(b)an additional increase in overturning moment resisted by axial
forces in the walls at each level corresponding to the increase in
the sum of the nominal capacities of the coupling beams above the
level under consideration required to resist the accidental torsion.

Forces @ Plastic Hinge Level

Forces @ Plastic Hinge Level

21.6.8.13


In lieu of a more detailed assessment, wall
segments that act as tension flanges in the
flexural mode shall be assumed to have no
shear resistance over the height of the
plastic hinge. For assemblies of wall
carrying torsion as a tube, the shear forces
in the tension flange shall be redistributed.

Clause 21


Moderate Ductility


Changes to the requirements for nominally
ductile frame systems reflecting the revised
R
d

value


Moderately ductile frame columns now
have be stronger than the frame beams


Revised frame column tie requirements
using the new confinement relations


Trigger added for tilt
-
up wall systems

Tilt
-
up Walls

21.7.1.2


Tilt
-
Up Wall Panels shall be designed to the requirements of
Clause

23 except that the requirements of Clause

21.7.2 shall apply
to wall panels with openings when the maximum inelastic rotational
demand on any part of the panel exceeds 0.02 radians and in no case
shall the inelastic rotational demand exceed 0.04 radians. The
requirements of Clause

21.7.4 shall apply to solid wall panels when
the maximum in plane shear stress exceeds



.



Note:
Methods for calculating rotational demand on elements of tilt
-
up panels with openings can be found in Explanatory Notes to CSA
Standard A23.3
-
04 published by Cement Association of Canada.
The seismic performance of tilt
-
up buildings depends not only on the
performance of the concrete wall panels, but also the performance of
the roof structure and the connection between the wall panels and
the roof. Only the design of the concrete wall panels is within the
scope of this standard.

'
1
.
0
c
c
f

Clause 21


Moderate Ductility


Rotational limit state design approach
introduced for moderately ductile walls


Simplified method included for cases with
moderate vertical loads or limited lateral
deflections


Special requirements for squat walls
introduced.

Squat Walls (Cl. 21.7.4)


Squat Shear Walls, h
w
/

w

≤ 2.0


R
d

= 2.0


Two possible hinge types


Flexural yield


Shear yield

Clause 21


Squat Walls

Clause 21 Changes


Added Sections


Requirements for R
d

= 1.5 buildings
introduced.


Frames


Walls


2
-
way slabs


New requirements for precast buildings.


Essentially ACI.



Clause 21 Seismic design


New section on structural diaphragms.


21.10.3.1


Diaphragm shall be idealized as a system consisting of the
following components arranged to provide a complete
load path for the forces:


(a)

chords proportioned to resist diaphragm moments as
tensions and compression forces.


(b)

collectors arranged to transfer the forces to, from and
between the vertical Seismic Force Resisting Systems.


(c)

either shear panels to transfer forces to, from and
between the chords and collectors or


(d)

continuous strut and tie in
-
plane shear trusses.

Clause 21 Seismic design


New section on foundations.


Essentially detailing rules


Extensive revisions to requirements for
structural elements not part of the Seismic
Force Resisting System.


Clause 21.12


Gravity Elements


Introduced rules for the treatment of “non
-
structural” concrete elements


Changes to the displacement limits that trigger
ductile, moderately ductile and conventional
detailing


Introduction of default requirements for the case
where detailed compatibility calculations are not
performed


New requirements for slab column connections.

Clause 21.12


Gravity Elements

Gravity Element Failure

Slab Punching Failure

Gravity Slab/Column (Cl. 21.12.3)


Slab Column Connections


Design for gravity two
-
way shear stresses


Calculations use EQ load combinations


R
E

is reduction in vertical punching shear capacity as a
function of interstorey deflection

0
.
1
005
.
0
85
.
0










i
E
R

Punching Test Data

Drift Ratios With and Without Shear Reinforcement
0
1
2
3
4
5
6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Vu/V0
Drift Ratio (%)
Dilger and Cao
Wey and Durrani
Robertson and Durrani
Pan and Mohle (92)
Pan and Mohle (89)
NBCC 2004 Drift Limit
Proposed Equation
Pan and Moehle 40% stress at 1.5% drift
IBC/SEAOC
Dilger & Cao SSR
Other Clauses


Clause 22 Plain Concrete


section added for unreinforced drilled piles


Clause 23 Tilt
-
Up Wall Panels


essentially unchanged,

m

goes from 0.65 to
0.75


Appendix D Anchorage


all new, introduces the method which was in
IBC 2000 and now ACI 318
-
02 as Appendix D


based on
square
35


angle cone

Appendix D

hd
1.5 hd
1.5 hd
1.5 hd
1.5 hd
35°
Acknowledgements


Perry Adebar and his graduate students at UBC


Ron DeVall of RJC


Vancouver Clause 21Committee


Patrick Lam


John Markulin


Andy Metten


Rob Simpson


Greg Smith


National A23.3 Seismic Subcommittee