masonry and shear

8/13/2019 Masonry and Shear

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Masonry

Masonry + shear



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)



Masonry

Behaving of masonry under

shear:



Masonry

V Ed

V Ed

Ed



Masonry

n shear failure of the bond between mortar

and units

n shear failure in mortar only



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



MasonryMasonry



Masonry

Test results:



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.



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



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;



Masonry



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



Masonry

n SHEAR WALLS

Masonry walls subjected to shear

n BASEMENT WALLS



Masonry

Basement and retaining walls

n Structural model,

n inner forces: M, N, V

n Check sliding along the insulation



Masonry

Shear walls



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



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).



Masonry

Calculation of load carried by one wall

(statically determinate system)



Masonry



Masonry

12 126

l x = 30

B

C

A 4

x A =

2

l y = 1 2

6W x

W yy

x



Masonry

Stiffness of shear walls

n elastic

n htot : l 2

¨ shear effect could be neglected (assume stiffness in bending

only

n including flanges



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



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:



Masonry



Masonry

Analysis of shear wallsn The most unfavourable combination of vertical load and shear

max Nmin N

max V



Masonry

n vertical loading

n bending moments

n V Ed ≤ V Rd

n N Ed ≤ N Rd



Masonry

Simplified calculation method for

shear walls

masonry and shear

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