G = 0.85 for rigid structure
Cp (refer to fig. 113)
Gcpi = ± 0.18 for fully enclosed building.
Cp & Kz
Design Wind Pressure for Signs
q
h
= wind pressure at top of sign
G = wind gust coefficient
A
s
= area of the face of sign
C
f
= force coefficient affected by sign dimension and clear area ratio
(for B/s = 4 see table 16). B=width of sign & s=height of sign &
h=elevation from ground to top of sign.
F = q
h
GC
f
A
s
Snow Load
Parameter that affects snow load:
Roof geometry, Wind exposure, Location, Importance, Heated structure or not
For roof slope < 5% then multiply snow load (p
g
) by the following factors:
p
f
= 0.7C
e
.C
t
.I.p
g
Where:
C
e
= 0.8 in an unobstructed area & 1.2 if sheltered in a large city.
C
t
= 1.2 for unheated structures & 1.0 for heated structures
I = 0.8 for agriculture and storage facilities & 1.2 for hospitals
Conditions:
if p
g
≤ 0.96 kN/m
2
then use the larger of p
f
= 0.7C
e
.C
t
.I.p
g
or p
f
= I.p
g
If p
g
> 0.96 kN/m
2
then use pf = I. 0.96 kN/m
2
Snow Loads on Roof
Earthquake Loads
Caused by ground motion and lateral resistance of the structure
Magnitude depends on:
Ground acceleration
Mass
Stiffness of the structure
Earthquake Loads
Two types of analysis:
1.
Dynamic Analysis:
Recommended for high rise and important structures
Elaborate and requires the use of computers
2.
Static Analysis
Used for small structures
Replaces dynamic loads by static loads to find base shear
Earthquake Disasters
Earthquake, Chile (2010)
Structural Design
In construction error can happen due to:
Variability in material property
Accidental loading due to vibration or impact
Material corrosion or decay
Therefore safety factor must be introduced to design the methodology to
account for uncertainties
Two methods:
1.
Working stress method
Maximum allowable stress = elastic limit
Loads are then multiplied by safety factor
Load Combination:
D
0.6 D + 0.6W
0.6 D + 0.7 E
Structural Design
Two methods:
2.
Stress Design or LRFD (Load and Resistance Factor Design)
Maximum allowable stress = ultimate strength in concrete and
plastic strength in steel
Material safety factor and load safety factor are separated
Load Combination:
1.4D
1.2D + 1.6L + 0.5S
1.2D + 1.5E + 0.5L
Earthquake, Wind, Snowloads
Earthquake footage in Japan Earthquake

2013
Fo
Hurrican Katrina  2007
AEGs
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 Spring '17
 Structural Engineering, Truss, Construction terminology, Structural load