Figure 4.1 : Wall acting as end support
(2)P Walls acting as end supports to floors or roofs that are subjected to wind loading shall be designed according to 4.2.2 only if:
0,12qri.h2
NSd where:
h is the clear storey height, in metres ;
qd is the design wind load on the wall per unit area of the wall, in kN/m2;
NSd is the minimum design vertical load on the wall at the top storey, in kN/m ;
t is the actual thickness of the wall, or the loadbearing leaf of a cavity wall, acting as an end support, in metres.
(3) As an alternative to obtaining t from equation (4.2), t may be determined from the design method given in 4.1 of ENV 1996-1-3, provided that the minimum design vertical stress at the mid-height position of the top storey wall is 0,15 N/mm2 or less and provided that neither major collapse nor total loss of stability of the building would result in the event of the failure of the top storey section of wall under consideration.
(4) If the method stated in clause (3) is adopted for the design of the wall then the vertical load resistance of the wall NRd should be derived from a presumed eccentricity at the ends of the wall of 0,41 and a bearing depth of 0,21 (see C1 (3) & (4) of Annex C to ENV 1996-1 -1).
4.2.2 Determination of design vertical load resistance of a wall
4.2.2.1 General
(1)P Under the ultimate limit state it shall be verified that:
NSd^NRd where:
NSd is the design vertical load on the wall ;
NRd is the design vertical load resistance of the wall according to clause 4.2.2.2.
4.2.2.2 Design vertical load resistance
(1) The design vertical load resistance NRd may be determined from : 0>.fk.A
where:
O is the capacity reduction factor allowing for the effects of slenderness and eccentricity of the loading, obtained from 4.2.2.3 ;
fk is the characteristic compressive strength of the masonry ;
is the partial factor for the material, obtained from 2.3 ;
A is the net area of the masonry, taking into account any openings.
(2) The characteristic compressive strength of the masonry, f^, should be obtained from 3.6.2 of ENV 1996-1 -1, or from use of a simplified approach.
NOTE : A simplified method for obtaining fk is given in Annex D.
4.2.2.3 Capacity reduction factor
(1) The capacity reduction factor O may be determined from :
*ef hef is the effective height of the wall (see 4.2.2.4);
tef is the effective thickness determined in accordance with 4.4.5 of ENV 1996-1-1 ;
O is the capacity reduction factor which incorporates the buckling effect, the accidental eccentricity, the eccentricity due to loads and the creep effect.
4.2.2.4 Effective height of walls
(1) The effective height may be determined by where :
h is the clear storey height;
pn is a reduction factor where n = 2, 3 or 4 depending on the edge restraint or stiffening of the wall.
(2) The reduction factor pn may be determined as follows.
(i) For walls laterally and rotationally restrained at top and bottom only by reinforced or prestressed concrete floors or roof (see figure 4.2) and having a bearing of at least 2/3 the thickness of the wall, but not less than 85 mm :
hef = Prrh
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