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

s
50,
mm
2
s
50,
mm
2
ing
ing
Earthquake loads
100
Earthquake loads are quite different in that they actually
originate with mass of the building itself. All buildings
have a mass from the weight of components used in their
construction. When an earthquake occurs, this causes
a horizontal movement of the ground. For the ground
to reach a certain horizontal velocity, it must be given an
acceleration to achieve this velocity, as it is initially at rest
with zero velocity. This acceleration applied to the building
mass, will cause a horizontal force to be applied to all
Varies
Varies
Varies
components 200, 250 of the building, 250 or 300 which mmmust
be 250 resisted or 300 by mm
the or structure. 300 mm These forces in effect work in the 70 reverse End Bearing
100
direction TYPE to 5wind
loads, TYPE as they 7are
imparted TYPE to 50 the Side building 9Bearing
from the foundations up. As the earths’ surface moves in
an earthquake, it can be likened to ripples on the surface of
a pond. As each ripple passes, the earths surface is moved
first in one direction and then in the reverse direction, in
a cyclic motion. The forces imparted to the building are
applied in one direction and then the completely opposite
direction. These forces can be applied from any direction
on the structure as the earthquake could be located on any
of the 360 degrees on the compass. The cyclic movements
can cause Variesan
oscillating motion Varies to be set up in Varies a building
200, 250 250 or 300 mm 250 or 300 mm
with a frequency, or number of oscillations per minute,
or 300 mm
dependant TYPE 5on
how rigid TYPE the structure 7 is. On TYPE multi-storey 9
buildings, this can mean that the ground surface is moving in
one direction while the top of the building is still moving in
the reverse direction. It can also mean that if the structure
has a different natural frequency to the earthquake, the
structure can get out of sync, with a resultant magnification
of forces. Seismic forces are determined from a large
number of factors dependant on the type of structure, its
size, and location, and are expressed as a proportion of the
acceleration due to gravity.
2.2.1.2 Distortion Under Load
70 End Bearing
50 Side Bearing
2.2.1.3 Unloaded Diagonal wall outline Bracing
To brace or stiffen a structure, it is necessary to define each
section of Deformed the structure wall outline with after triangular application shapes. This is the
of loads (exaggerated) at top of wall
Horizontal
only shape that will lock all points in relative positions wind to or
each other. In a structure, these triangles become lines load of
force, and Inherent there stiffness must be at corners structural keeps members wall in place to
close to perpendicular under load
allow these forces to connect in a triangular lattice.
These diagonal braces will keep the corners of the walls
in the Plan same View relative of Walls position Without to each Diaphragm other but if this is
the only bracing used, the top of the walls are still free to
distort along their length.
Unloaded
Unloaded
wall
wall
outline
outline
Distortion of walls reduced and all corners move same
amount Plan View assuming of Walls infinitely Without stiff diagonal Diaphragm
bracing
Plan View of Walls With Diagonal Bracing
Unloaded and loaded
2.2.1.4 wall outline Diaphragm Action
Installation of loads of a (exaggerated) diaphragm at or top a of stiff wall panel that connects to
Horizontal
all top edges of the walls will prevent this distortion, wind as this or
flat panel is effectively an infinite number of diagonal load Horizontal braces
side by side that make Diagonal up bracing into a solid surface.
load
The floor diaphragm spreads the applied loads to all top
edges Distortion of the of supporting walls reduced walls and all and corners the move walls same parallel to the
amount assuming infinitely stiff diagonal bracing
applied loads resist these forces by also acting as vertical
diaphragms Top Plan of all View walls or of bracing held Walls in position walls. With by These Diagonal diaphragm loads and Bracing are transferred
into resisting the foundations forces to applied at the loads base spread of evenly these around walls by shear
wall lines
Deformed wall outline after application
of loads (exaggerated) at top of wall
Inherent stiffness at corners keeps wall
close to perpendicular Diagonal bracing under load
A simple four walled building, without a floor or ceiling/roof
forces.
Plan View of Walls Locked in Place
diaphragm, that has loads applied horizontally to it from
Unloaded and loaded by a Diaphragm
wall outline
wind or earthquakes, is able to distort. The only resistance
to these loads is from any inherent stiffness in the walls,
especially at corner junctions.
Such a building, without a diaphragm acting as a stiff lid, will
be “floppy” and free to distort under wind Horizontal or earthquake applied loads parallel to panel axis
loads.
Unloaded wall outline
Top of all walls held in position by diaphragm and
resisting forces to applied loads spread evenly around
C1 C2 C3 C4 wall C5 lines C6
Horizontal applied loads parallel to panel axis = w kN/m
Deformed wall outline after application
of loads (exaggerated) at top of wall
Inherent stiffness at corners keeps wall
Horizontal
wind or
earthquake
load
Plan View of Walls Locked in Panel Place outlines
by a Diaphragm
close to perpendicular under load T1 T2 T3 T4 T5 T6
C7 C8 C9 C10 C11 C12 C13 C14
Plan Reaction View force of Walls in Without Diaphragm Horizontal applied loads parallel to panel axis
bracing wall to
Reaction
force in
foundation
bracing wall
to foundation
Infinate number of diagonal
braces in diaphragm
Deformed wall outline after application
Reaction force in
bracing wall to Reaction
force in
foundation bracing wall
to foundation
SFP Unloaded 2012 wall outline
32 Copyright © Supercrete Bending Limited 2008
T7 T8
Unloaded wall outline
S
T9 T10 T11 T12 T13
L
Infinate number of diagonal
braces in diaphragm
moment
diagram
earthquake
Horizontal
wind or or
earthquake
load
earthquake
wind or
earthquake
Horizontal
wind or
earthquake
load
React
force
bracin
to fou
React
force
bracin
to fou
M max. = wS
8n
M max. = wS
8n