In this article, we will follow the rules from EN1996-1-1 to verify an unreinforced masonry wall subjected to an in-plane lateral force.
Keywords: Advance Design, Masonry, Eurocode 6, EN1996-1-1
Masonry can effectively carry compressive forces but this material only has moderate capacity when it comes to shear.
Yet, masonry walls may be exposed to wind forces that could cause shear failure mechanisms, especially on the top levels, where the compressive forces are moderate.
Therefore, shear resistance of masonry walls must be properly assessed.
Eurocode 6 provides a method in that regard.
2. Sliding shear resistance of an unreinforced masonry wall
Unreinforced masonry walls subjected to shear loading are covered in section 6.2 from EN1996-1-1.
As usual with the Eurocodes, a design force (VEd, design shear force) is compared to a resisting force (VRd, shear resistance).
Assume the following wall:
Initial shear strength: fvk0 = 0,20 MPa
Compressive strength: fk = 5,00 MPa
Partial factor for material: γM = 2,2
2.2. Shear resistance VRd
Shear resistance VRd is defined in eq. (6.13).
First of all, we need to estimate the compressed length of the wall (lc).
The VEd lateral force is indeed creating an in-plane moment that can cause tension at the bottom part of the wall, especially if the compressive forces are low.
- Moment at the bottom of the wall
- Compressed length lc
The eccentricity exceeds 1/6 of wall length.
Assuming a linear distribution and based on the equilibrium of force and moment:
We can assess the length of the compressed part of the wall:
- Shear strength fvd
Assuming all joints (vertical and horizontal) are filled with mortar, we compute the characteristic shear strength fvk with eq.(3.5).
The design compressive stress σd can slightly increase fvk.
fvk does not exceed
The design shear strength is then given by:
- Shear resistance VRd
We can finally compute shear resistance VRd from eq. (6.13):
Sliding shear verification:
The sliding shear verification is passed.
This verification can prevent some of the shear failure mechanisms that may occur in masonry buildings.
Of course, hand calculation might be tedious.
Fortunately, our upcoming Advance Design module, dedicated to masonry wall design, will perform this verification, among others, in a matter of seconds and provide a detailed calculation report, with intermediate values and reference to the EN1996-1-1.
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