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8/13/2019 Masonry and Shear
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Masonry
Masonry + shear
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Masonry
n Walls subjected to
lateral loading
n Shear walls
n basement walls
n retaining walls
n walls subjected to wind load
¨ reinforced masonry¨ usually not needed (not
decisive)
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Masonry
Behaving of masonry under
shear:
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Masonry
V Ed
V Ed
Ed
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Masonry
n shear failure of the bond between mortar
and units
n shear failure in mortar only
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MasonryMasonry
n adhesion between units and mortar
n tensile strength of mortar
n shear strength of masonry unitn strength of masonry unit in the direction of
normal stress
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MasonryMasonry
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Masonry
Test results:
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Masonry
Shear strength of masonry
n f vk = f vk0 + 0,4 d
n The characteristic shear strength of
masonry is a function of the¨characteristic initial shear strength of the
masonry
n given in a table
¨and the design compressive stress orthogonalto the shear plane being considered.
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Masonry
n f vk characteristic shear strength of masonry,
using
¨ general purpose mortar
¨ thin layer mortar in beds (0,5 mm to 3,0 mm)
¨ lightweight mortar
n with perpend joints
f vk = f vk0 + 0,4 d
f vk = 0,5 f vk0 + 0,4 d
¨ but not greater than f b or f vlt
filledunfilled
0,065
0,045
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Masonry
n f vk0 characteristic initial shear strength, under
zero compressive stressn f b is the normalised compressive strength of
the masonry units
n f vlt is a limit to the value of f vk
n d is the design compressive stressperpendicular to the shear in the member at the
level under consideration, using the appropriate
load combination based on the average vertical
stress over the compressed part of the wall thatis providing shear resistance;
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Masonry
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Masonry
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Masonry
Resistance V Ed
≤ V Rd
n V Rd = f vd t l c n V Rd = f vd b l c
for f vk calculation
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Masonry
n SHEAR WALLS
Masonry walls subjected to shear
n BASEMENT WALLS
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Masonry
Basement and retaining walls
n Structural model,
n inner forces: M, N, V
n Check sliding along the insulation
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Masonry
Shear walls
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Masonry
Shear walls
n Resistance to horizontal actions is generally provided bya system, formed by the floors and shear walls.
n Horizontal actions:¨ wind loads,
¨ effects due to the imperfection (angle ) ,
¨ others in special cases
n Openings in shear walls can considerably affect theirbehaviour, their presence should be taken into account.
n Chases and recesses reduce the shear capacity of a
wall.
toth100
1=ν
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Masonry
n For the distribution of horizontal actions only, the elastic
stiffness of the shear walls, including any flanges, shouldbe used.
n If the floors can be idealised as rigid diaphragms, (forexample, in the case of in-situ concrete slabs) aconservative procedure is, to distribute the horizontalforces to the shear walls, in proportion to their stiffness,on the assumption that all deflect by the same amount.
n Where the plan arrangement of the shear walls isasymmetric, or for any other reason the horizontal forceis eccentric to the overall stiffness centre of the structure,account shall be taken of the effect of the consequent
rotation of the system on the individual walls (torsionaleffects).
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Masonry
Calculation of load carried by one wall
(statically determinate system)
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Masonry
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Masonry
12 126
l x = 30
B
C
A 4
x A =
2
l y = 1 2
6W x
W yy
x
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Masonry
Stiffness of shear walls
n elastic
n htot : l 2
¨ shear effect could be neglected (assume stiffness in bending
only
n including flanges
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Masonry
Flange of a shear wall
n A limited portion of an intersecting wall can
act as a flange to a shear wall, increasing
its stiffness and strength:
1) the lesser of: htot /5 ,
l s /2 ,
h /2 ,
6 t ;
2) intersecting wall
3) shear wall
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Masonry
Analysis of shear walls
n For the analysis of shear walls, the designhorizontal actions and
n the design vertical loads shall be applied to the
overall structure.n This causes the following situation of the
individual shear wall:
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Masonry
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Masonry
Analysis of shear wallsn The most unfavourable combination of vertical load and shear
max Nmin N
max V
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Masonry
n vertical loading
n bending moments
n V Ed ≤ V Rd
n N Ed ≤ N Rd
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Masonry
Simplified calculation method for
shear walls