CEE 626 MASONRY
DESIGN
Seismic, Anchors and
lateral loads Out-ofplane
Slide Set 7
Spring 2015
1
TMS 402 Part 2
Design Requirements

Ch. 4: General Analysis &
Design Considerations

Ch. 5: Structural Elements

Ch. 6: Details of
reinforcement, metal
accessories & anchor bolts

Ch. 7 Seismic design
requirements
2
Seismic Design:
TMS 402 Chapter 7

Applies to all masonry except


Walls must either be
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isolated from the seismic force - resisting system
classified as shear walls
Objective is to improve performance of masonry
structures in earthquakes
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glass unit masonry and veneer
improves ductility of masonry members
improves connectivity among masonry members
Requirements for AAC masonry differ slightly
Slide 3
Seismic Design:
TMS 402 Chapter 7

Assign a structure’s Seismic Design Category
(SDC) according to ASCE 7 - 10


SDC depends on seismic risk (geographic location),
risk category (importance), underlying soil
SDC determines


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required types of shear walls (prescriptive
reinforcement)
prescriptive reinforcement for other masonry
elements
permitted design approaches for LFRS
Slide 4
Seismic Design:
TMS 402 Chapter 7

Seismic design requirements
are based on ASCE 7 - 10
Seismic Design Categories
(from A up to F)

Requirements are
cumulative; requirements in
each “higher” category are
added to requirements in the
previous category
Slide 5
Minimum Reinforcement, Shear
Wall (SW) Types
SW Type
Minimum Reinforcement
SDC
Empirically
Designed
none
A
Ordinary Plain
none
A, B
Detailed Plain
Vertical reinforcement = 0.2 in.2 at corners, within 16
in. of openings, within 8 in. of movement joints,
maximum spacing 10 ft; horizontal reinforcement W1.7
@ 16 in. or #4 in bond beams @ 10 ft
A, B
Ordinary
Reinforced
same as above
A, B, C
Intermediate
Reinforced
same as above, but vertical reinforcement @ 4 ft
A, B, C
Special
Reinforced
same as above, but horizontal reinforcement @ 4 ft,
and  = 0.002
any
Slide 6
Seismic Design:
TMS 402 Chapter 7

Seismic Design Category A



drift limit of 0.007 from ASCE 7 - 10 (Section 12.12.1)
for typical masonry structures
minimum design connection force for wall - to roof
and wall - to - floor connections from ASCE 7 - 10
(Section 12.11.2)
Seismic Design Category B

lateral force – resisting system cannot be designed
empirically
Slide 7
Seismic Design:
TMS 402 Chapter 7

Seismic Design Category C


Shear walls must meet minimum prescriptive
requirements for reinforcement and connections
(ordinary reinforced, intermediate reinforced, or
special reinforced)
Other walls must meet minimum prescriptive
requirements for horizontal or vertical reinforcement
Slide 8
Requirements for Detailed Plain SWs
and SDC C: TMS 402 Section 7.3.2.3
roof connectors
@ 48 in. max oc
roof
diaphragm
#4 bar (min) within
16 in. of top of parapet
Top of Parapet
#4 bars around
openings
#4 bar (min)
within 8 in. of
corners &
ends of walls
24 in. or 40 db
past opening
#4 bar (min) @
diaphragms
continuous
through control
joint
#4 bar (min)
within 8 in. of
all control joints
control joint
#4 bars @ 10 ft oc
#4 bars @ 10 ft oc or W1.7 joint
reinforcement @ 16 in. oc
Slide 9
Seismic Design:
TMS 402 Chapter 7

Seismic Design Category D



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Masonry that is part of the lateral force – resisting
system must be reinforced so that v + h  0.002,
and v and h  0.0007 (Special Shear walls)
Type N mortar and masonry cement mortars are
prohibited in the seismic force – resisting system
Shear walls must meet minimum prescriptive
requirements for reinforcement and connections
(special reinforced)
Other walls must meet minimum prescriptive
requirements for horizontal and vertical reinforcement
Slide 10
Requirements for Special Reinforced
Shear Walls: TMS 402 Section 7.3.2.6
roof connectors
@ 48 in. max oc
roof
diaphragm
#4 bar (min) within
16 in. of top of parapet
Top of Parapet
#4 bars around 24 in. or 40 db
openings
past opening
#4 bar (min)
within 8 in. of
corners &
ends of walls
#4 bar (min) @
diaphragms
continuous
through control
joint
#4 bar (min)
within 8 in. of
all control joints
control joint
#4 bars @ 4 ft oc, 1/3 h, or
1/3 L
#4 bars @ 4 ft oc, 1/3 h, or
1/3 L
Slide 11
Seismic Design Categories E and
F: TMS 402 Section 7.4.5

Additional reinforcement requirements for masonry
not laid in running bond and used in
nonparticipating elements
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Horizontal Reinforcement of at least 0.0015 Ag
Horizontal Reinforcement must be no more than 24 in.
oc.
Must be fully grouted and constructed of hollow open-end
units or two wythes of solid units
Slide 12
Reinforced Masonry
Allowable (ASD) –
For Special Shear Walls
Special considerations for Special
Shear Wall design See Ch 7 in Code
For Special shear walls - fv = 1.5 V/Anv
Reinforced Masonry
Allowable (ASD) – Additional Stuff
For Special Shear Walls
Special considerations for Special
Shear Wall design limit Total Steel
Reinforced Masonry Shear Walls
Strength Design –Additional stuff (SD)
Special considerations for Shear wall design – Mostly
related to Seismic loading – See Ch 7 in Code
SD – Limits on Max amount of reinf. - depends on SDC –
(ASCE 7) – and type of shear wall
-
Make sure you have enough Shear capacity to ensure
flexure failure when flexural dominated walls
-
Prescriptive Shear reinforcing amounts depending on
SDC – (ASCE 7) – and type of shear wall
Shear Wall Maximum Reinforcement
STRENGTH DESIGN ONLY
a = 3 for intermediate
shear walls R = 3.5
= 4 for special shear walls
R=5
For walls designed with
Seismic R ≤ 1.5 & M/Vd≤1
There is no limit on reinforcing
all other a = 1.5
Note Detail and Reinforced
Shear Walls R = 2 ,URM R = 1.5
Shear Wall Maximum Reinforcement
STRENGTH DESIGN ONLY
a = 3 for intermediate
shear walls R = 3.5
= 4 for special shear walls
R=5
For walls designed with
Seismic R ≤ 1.5 & M/Vd≤1
There is no limit on reinforcing
all other a = 1.5
Note Detail and Reinforced
Shear Walls R = 2 ,URM R = 1.5
Reinforced Masonry
Special Shear Walls Strength Design
– Prescriptive Shear reinforcing amounts depending on
SDC – (ASCE 7) – and type of shear wall (SD)
On board
SEE MDG CH 10 -4-6
On board
On board
Limit Design – Appendix C

New to 2013 TMS 402

May be used as an option for Special Reinforced
Shear Walls
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Sophisticated Analysis Method

Perforated Walls
Slide 22
Limit Design: Seismic Design of
Reinforced Masonry Structures
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force - based design (ASCE 7 - 10)
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emphasizes strength
displacement - based design (no code provisions
yet)
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emphasizes deformation
Slide 23
Force-based Seismic Design
Limitations

uncoupled cantilever walls are easy
to design

coupled cantilever walls are more
difficult to design

walls with arbitrary openings may be
impossible to design rationally
Slide 24
Limit Design: Seismic Design of
Reinforced Masonry Structures

Design Methodology

Seismic Analysis > Yield Mechanism > Verify Strength and Displacement
vs.
Full Structure Hinging
Base Hinging
Slide 25
Reinforced Masonry
Allowable (ASD) & Strength (SD)
Anchors:
Anchors bolts – headed and bent bolt in
masonry – ASD and SD provisions essentially
the same and have been calibrated to the
different load levels
- see Ch 8.1.3 ASD and 9.1.6 (SD) also areas
defined in 6.2
not covered in course
Look first at Out of Plane Loads
Need to account for openings
vertical
strips
roof diaphragm
horizontal
strips
`
If the Door spans
vertically the load is
increased
If the windows span
vertically the load is
increased
Ends of Walls usually have
higher wind loads
Also may get an increase in vertical loads due to beam reactions over openings
The question is how much of the wall is effective around the openings – Typically assume effective width
On board
On board
On board
Lateral Loads – Cavity Walls
Also known as Multi wythe-non composite walls
Lateral Loads – Cavity Walls
Also known as Multi wythe-non composite walls
•
•
Code requires Axial
load to be carried by
only the wythe it is
applied to – Same for
in-plane loads
But out of plane
Moment can be
shared between
wythes w.r.t stiffness
Lateral Loads – Cavity Walls
Also known as Multi wythe-non composite walls
•
•
Note that air space
crossed by ties
Air space needs to be
1” min (2” recom.)
and a maximum of
4.5”
Lateral Loads – Cavity Walls
•
Note that 3EI/L is for a pin at the far
end (it would be 4EI/L if it was fixed
Lateral Loads – Cavity Walls
Lateral Loads – Cavity Walls
In this case the ties at the top will act as the reaction
for the outer wythe and can be heavily loaded
Lateral Loads – Cavity Walls
In this case the ties at the top will act as the reaction
for the outer wythe and can be heavily loaded
Lateral Loads – Cavity Walls
1
2
900 (2ksi) = 1,800 ksi
700 (4ksi) = 2,800 ksi
5.63
3.63
321,216
133,930
455,146
0.706
0.294
Lateral Loads – Cavity Walls
= 0.706
=271w + 1765 (lb.in) with w in psf)
= 4.28w + 27.88
fb1 <= 61 psi (table in Code for Fully grouted Type S)
Note this is for D + L + W (OLD Load
Combos)
Also need to look at .6 D + 0.6W &?
= -23.1+ 4.28w + 27.88 = 61 so
w = 13.1 psf
Lateral Loads – Cavity Walls
= 0.294
M2= 112.9w + 735
fb2
= 4.29w + 27.95
<= 24 psi (table in Code for Fully solid Type S)
= -7.3+ 4.29w + 27.94 = 24 so
w = 0.78 psf
Lateral Loads – Cavity Walls
•
•
•
•
•
Note the brick will crack first and limits loading
But the code allows you to allow the brick to
crack if it is a veneer and the backing system
takes all the load
In this case:
This would mean the block would take all the
load i.e. DF =1.0 – redo. Calcs.- gives w = 7.35 psf
So this “w” would be the best you could get out
of this wall configuration. Look at ASCE Load
Combo’s and how this will change result