Structural Floor Panels Design Guide - Hebel Supercrete AAC ...

2.2.4.3 Parallel Loads
Analyse the panels for loads parallel to the floor
panel axis. The governing panels will normally be in the
diaphragm with the greatest number of panels.
a) Calculate the maximum tensile force in the reinforcing
steel in the first joint (from the outer edge of the
diaphragm).
T = (w x L) - (w x 0.6)*
2 * for full width 600mm panel
b) Calculate the steel area required for this tensile force
As = T
fy
It is not advisable to use high tensile steel for the ring
anchor reinforcing, as the use of high tensile steel with low
compressive strength Supercrete AAC could lead to an
explosive failure of the Supercrete. It is not balanced
design philosophy to use high strength steel in low strength
concrete.
If the area of reinforcing required is calculated to be less
than 12 mm in diameter, use a 12 mm deformed bar. If the
bar area required is more than 12 mm diameter, then the
steel area in the next joint must also be calculated.
In this case, T = (w x L) - (w x 2 x 0.6)
2
and subsequent joints should be similarly checked if
required.
The diagonal compression force in the Supercrete panels
is then calculated :
C = T max
Cos where = Tan
If this force exceeds 10 kN, then a corner chamfer is
required on the outer panels until the diagonal force
reduces to less than 10 kN in the inner panels of the
diaphragm. Panels should only be notched if they are
200mm thick or greater – it may be necessary to increase
the panel thickness to accommodate the diagonal
forces. The maximum ultimate compressive stress in the
Supercrete AAC is 4 MPa. The required length of the
chamfer is therefore given as:
Where Lc = length of chamfer in both directions in mm
-1(0.6)
(S)
Lc = C
0.6 x D x 4√2
C = Diagonal compressive force in Newtons
D = Panel thickness in mm
The length of the chamfer should normally only be required
to be approximately 100mm, and a maximum of 150mm.
Higher values will compromise the end bearing and shear
capacity of the panel, which also need to be checked
anyway.
c) Calculate the tensile force in the perimeter ring anchor
steel perpendicular to the applied external forces.
T = wL2 8 x 0.7 x S
Where w = Externally applied horizontal load in N/m
L = Length of diaphragm perpendicular to
applied load in metres
S = Length of panel parallel to applied loads
d) Calculate the steel area required for this tensile force
As = T
SFP 2012 38 Copyright © Supercrete Limited 2008
fy
2.2.4.4 Perpendicular Loads
Analyse the panels for loads applied perpendicular to the
panel axis.
a) Calculate the maximum bending moment in each panel:
Mmax = wS
Where w = Externally applied horizontal load in N/m
S = Length of panel perpendicular to applied
loads
n = Number of panels in diaphragm
2
8n
b) Calculate the width of the compression block in the
AAC in accordance with standard reinforced concrete
beam analysis
Where a = width of compression block in mm
As = Area of ring anchor steel in panel joint in
mm2 a = As. fy
3.4 x D
fy = Yield strength of reinforcing steel in MPa
D = Thickness of panel in mm
c) Calculate moment capacity of each panel
Mc = Ø.As. fy(600 – (0.5a)) x 10 -3
Where Mc= Moment capacity of panel in N-m
Ø = Capacity reduction factor
As = Area of ring anchor steel in panel
joint in mm2 fy = Yield strength of reinforcing steel in MPa
a = Width of compression block in mm
d) If the moment capacity of the panel exceeds Mmax,
then they have sufficient bending capacity.
Determine the shear force per metre that needs to be
transferred into the support walls
= wS
2L
Normally this shear force is resisted by the vertical bars
in the Supercrete Block support walls, or in the case of
steel support beams, by the cleats on top of the beams,
and capacity of these is sufficient. If not, additional cleats or
shear dowels may be required.