1. 1
! Introduction
! Fundamental of Structural Theory
! Classification
! Loads
! Structural Design
TYPES OF STRUCTURES AND LOADS
2. 2
Introduction
• Design of Structures
- Safety
- Esthetics
- Serviceability
- Environment
- Economy
• Structure
“….. a system of connected parts used to support a load…..”
• Analysis of Structures
- Strength
- Rigidity
• Idealization of Structures
- Physical Model
- Mathematical Model
3. 3
Fundamental of Structural Theory
• Idealization
• Physical Model
• Members
• Connections
• Supports
• Loads
• Free-body Diagrams
• System
• Member
• Mathematical Model
• Equilibrium Conditions
• Compatibility Conditions
• Constitutive Relationship
8. 8
Trusses
• Types of Structures
Cables and Arches
cables support their loads in tension arches support their loads in compression
compression
tension
10. 10
Loads
• Dead Loads
• Live Loads
• Building Loads
• Bridge Loads
• Wind Loads
• Snow Loads
• Earthquake Loads
• Hydrostatic and Soil Pressure
• Other Natural Loads
11. 11
Table 1-1 Codes
Manual for Railway Engineering, American Railway Engineering Association
(AREA)
General Building Codes
Minimum Design Loads for Building and other Structures, ANSI / ASCE 7-95,
American Society of Civil Engineers
*Basic Building Code, Building Officials and Code Administrators International
(BOCA)
*Standard Building Code, Southern Building Code Congress International
*Uniform Building Code, International Conference of Building Officials (UBC)
Design Codes
Building Code Requirements for Reinforced Concrete, Am. Conc. Inst. (ACI)
Manual of Steel Construction, American Institute of Steel Construction (AISC)
Standard Specifications for Highway Bridges, American Association of State
Highway and Transportation Officials (AASHTO)
National Design Specification, American Institute of Timber Construction (ATTC)
16. 16
Where,
L = reduced design live load per square foot or square meter of area supported
by the member, > 0.5 Lo for 1 floor, > 0.4 Lo for 2 floors or more
Lo = unreduced design live load per square foot or square meter of area
supported by the member (see Table 1-4)
AI = influence area in square feet (> 400) or (>37) square meters, equal to four
times the tributary or effective load-carrying floor area for a column, and
two times the tributary or effective load-carrying floor area for a beam*
(FPS units)L = ( 0.25 +
15
AI
(
(SI units)L = ( 0.25 +
4.57
AI
(
The reduced load L
• >.50 Lo , for floor (2-story)
• >.40 Lo , for floor (>2-story)
• =1.00 Lofor roof, public hall, parking garage
Lo
Lo
17. 17
Live Load
Occupancy or Use psf kN/m2
Assembly areas and theaters
Fixed seats 60 2.87
Movable seats 100 4.79
Dance halls and ballrooms 100 4.79
Garages (passenger cars only) 50 2.40
Office buildings
Lobbies 100 4.79
Offices 50 2.40
Storage warehouse
Light 125 6.00
Heavy 250 11.97
Residential
Dwellings (one- and two-family) 40 1.92
Hotels and multifamily houses
Private rooms 40 1.92
Public rooms 100 4.79
Schools
Classrooms 40 1.92
Corridors above first floor 80 3.83
Table 1-4 Minimum Live Loads*
18. 18
Example 1-1
The floor beam in the figure below is used to support the 2 m width of a
lightweight plain concrete slab having a thickness of 10 cm. The slab serves as a
portion of the ceiling for the floor below, and therefore its bottom is coated with
plaster (25 kg/m2). Furthermore, an 2.5 m height, 30 cm thick masonry wall is
directly over the top flange of the beam. Determine the loading on the beam
measured per foot of length of the beam.
30 cm.
2.5 m.
1 m. 1 m.
10 cm.
plaster
20. 20
30 cm.
2.5 m.
1 m. 1 m.
10 cm.
14 kN/m (1430 kg/m)
Concrete slab: )2400( 3
m
kg 480)1.0)(2( =mm kg/m
Plaster ceiling: 50)2)(25( 2
=m
m
kg
kN/m
)360( 2
m
kg
Masonry wall: 900)5.2( =m kg/m
คอนกรีตเสริมเหล็ก 2400 kg/m3
อิฐมอญเต็มแผนฉาบปูน 360 kg/m2
Total load 1430= kg/m
21. 21
Example 1-2a
A two-story office building has interior columns that are spaced 7 m apart in two
perpendicular directions. If the (flat) roof loading is 100 kg/m2 determine the
reduced live load supported by the spread-footing foundation. Assume the ground
floor is a slab on grade.
At 7 m
7 m
7 m7 m
22. 22
At
SOLUTION: ANSI-based US Code
7 m
7 m
7 m7 m
FR = (100 kg/m2)(49 m2) = 4.90 T
For the second floor, the live load is taken from table 1-4:
Lo = 250 kg/m2 .
Since AI = 4At = 4(49 m2) = 196 m2 > 37.2 m2 , the live load can be reduced. Thus,
2
/144250)575.0(250)
)49(4
57.4
25.0()
4
57.4
25.0( mkgL
A
L o
T
==+=+=
The load reduction = (0.575) L0 > ( 0.50) L0 O.K. Therefore
FF = (144 kg/m2)(49 m2) = 7.044 T
The roof loading is 100 kg/m2
At = (7 m)(7 m) = 49 m2
23. 23
At 7 m
7 m
7 m7 m
For the ground floor, the live load is taken from table 1-4:
Lo = 250 kg/m2 . No live load reduction is allowed.
FG = (250 kg/m2)(49 m2) = 12.25 T
The total live load supported by the foundation is thus
F = FR + FF + FG = 4.90 + 7.044 + 12.25 = 24.19 T
24. 24
At
SOLUTION: Thai Code
7 m
7 m
7 m7 m
FR = (100 kg/m2)(49 m2) = 4.90 T
For the second and ground floor, the live load is
taken from table 1-4:Lo = 250 kg/m2 .
FF = (250 kg/m2)(49 m2) = 12.25 T
The total live load supported by thefooting is thus
F = FR + FF = 4.90 + 12.25 + 12.25 = 29.4 T
roof loading is 100 kg/m2
At = (7 m)(7 m) = 49 m2
25. 25
Example 1-2b
A eleven-story office building has interior columns that are spaced 7 m apart in
two perpendicular directions. If the (flat) roof loading is 100 kg/m2 and floor
loading is 250 kg/m2 determine the reduced live load supported by a typical
interior footing using the US code and Thai code.
At 7 m
7 m
7 m7 m
10
9
8
7
6
5
4
3
2
1
ground
roof deck
26. 26
At
SOLUTION
7 m
7 m
7 m7 m
For the second floor, the live load is taken from table 1-4:
Lo = 250 kg/m2 .
Since 4At = 4(49 m2) = 196 m2 > 37.2 m2 , the
live load can be reduced. Thus,
2
/144)250(575.0
250)
196
57.4
25.0(
)
4
57.4
25.0(
mkg
L
A
L o
t
==
+=
+=
The load reduction here is (0.575)L0 > (0.40)L0 O.K.
Therefore use 0.575 for all.
At = (7 m)(7 m) = 49 m2
For Thai code: see table 1-3b.
For the US code based on ANSI:
10
9
8
7
6
5
4
3
2
1
ground
roof deck
28. 28
Example 1-2c
A eleven-story office building has interior columns that are spaced 7 m apart in
two perpendicular directions. If the (flat) 15 cm-thick roof liveload is 100 kg/m2
and 20 cm-thick floor live loading is 300 kg/m2 determine the reduced live load
supported by a typical interior footing using the US code and Thai code.
At 7.5 m
7.5 m
7.5 m7.5 m
10
9
8
7
6
5
4
3
2
1
ground
roof deck
29. 29
At
SOLUTION
7.5 m
7.5 m
7.5 m7.5 m
For the second floor, the live load is taken from table 1-4:
Lo = 250 kg/m2 .
Since 4At = 4(56.25 m2) = 225 m2 > 37.2 m2 , the
live load can be reduced. Thus,
2
/4.166)250(555.0
300)
225
57.4
25.0(
)
4
57.4
25.0(
mkg
L
A
L o
t
==
+=
+=
The load reduction here is (0.555)L0 > (0.40)L0 O.K.
At = (7.5 m)(7.5 m) = 56.25 m2
For Thai code: see table 1-3b.
For the US code based on ANSI:
10
9
8
7
6
5
4
3
2
1
ground
roof deck
32. 32
I = <
L + 38.1
15.24
0.3
For highway c the AASHTO Specification gives the expression for
the impact factor as
In which L is the length in meter of the portion of the span loaded to cause the
maximum stress in the member under consideration.
2.9 T 9.1 T 4.6 T 8.2 T 8.2 T
4.2 m 1.2 m4.2 m
Bridge Loads
12 Ton Truck 21 Ton Truck
35. 35
p = q G C
Where,
q = basic pressure at the height of 10 m
= 0.613 KzKztV 2I (N/m2, m/s)
p = wind pressure
G = gust factor (0.85, typical)
C = shape factor
External Pressure: Formulation
36. 36
qhGCp
(p = qhGCp)side wall
qhGCp
qzGCp
wind
B
L
ridge
plan
qhGCp
qhGCp
qhGCp
qzGCp
q = 0. 613 KzKztV 2I q, N/m2
V , m/s
External Pressure on Main Wind-Resisting System
elevation
θ
z
h
4.6 m
39. 39
Total Wind
Pressure on the
Main Wind-Force
Resisting System:
Enclosed Building qzGCp
qhGCp
qhGCp
qhGCp
+
0.18qh
+
0.18qh
qhGCp
=
pz
ph
ph
ph
ph
A pz
ph
ph
ph
ph
B
=
40. 40
qz = 0.613 KzKztV 2I (N/m2)
Where,
V = the velocity in m/s of a 3-second gust of wind measured at 10 m
above the ground during a 50-year recurrence period. Values are obtained from
a wind map.
I = the importance factor that depends upon the nature of the building occupancy
(see Table 1-6)
Kz = the velocity pressure exposure coefficient, which is a function of height and
depends upon the ground terrain (use equation or see graph 1-1).
Kzt = a factor that accounts for wind speed increases due to hills and escarpments.
For flat ground Kzt = 1
q = qz for windward wall,
= qh for others
Detail:
p = q GCp - qh(GCpi)
GCp = ±0.18, enclosed building*
GCp = ±0.55, partially enclosed building*
GCp = ±0, open building*
42. 42
Exposure B
Urban and
suburban areas
Exposure A
Large city centers
Exposure C
Open terrain
Exposure D
Edge of large
bodies of water
Table 1-5 Exposure Categories for Buildings for Wind Loads
Constants
Exposure Category zg, m αααα G
Flat, unobstructed coastal areas D 213 11.5 0.85
Large city centers with at least 50% of the buildings having
heights in excess of 70 ft ( 21m) A 457 5.0 0.85
Urban and suburban areas with closely spaced obstructions of
the size of single family houses or larger B 366 7.0 0.85
Open terrain with scattered obstructions of heights generally
less than 30 ft (9 m) C 274 9.5 0.85
48. 48
All buildings other than those listed in Categories I, III and IV II 1.00
Buildings representing a substantial hazard to human life in
the case of failure, such as: those where more than 300 people
congregate in one area; schools and day-care facilities with
capacity greater than 250; colleges with capacity greater
than 500; hospitals without emergency treatment or surgery
facilities but with patient capacity greater than 50; jails, power
stations and utilities not essential in an emergency; and buildings
containing toxic and explosive materials III 1.15
Essential facilities, including hospitals, fire and police stations,
national defense facilities and shelters, communication centers,
power stations, and utilities required in an emergency IV 1.15
Building representing low hazard to human life in the
case of failure, such as agricultural and minor storage
facilities I 0.87
Table 1-6 Classification of Buildings for Environmental Loads
Importance Factor, I
Occupancy or use Category Wind loads
49. 49
Surface L/B Cp Use with
Table 1-7 Wall pressure coefficients, Cp
windward wall All values 0.8 qz
>
Leeward wall 0-1 -0.5
2 -0.3 qh
4 -0.2
Side walls All values -0.7 qh
51. 51
Wind Cp
direction h/L
Horiz distance from
windward edge
0 to h/2 -0.9
h/2 to h -0.9
h to 2h -0.5
>2h -0.3
0.5≤
1.0≥ 0 to h/2 -1.3**
>h/2 -0.7
Normal
to
ridge
for
θ < 10o
and
parallel
to
ridge
for
all θ
*Value is provided for interpolation
purposes
**Value can be reduce linearly with
area over which it is applicable
follows:
Area Reduction
(ft2) factor
100 (9.29 sq m) 1.0
250 (23.23 sq m) 0.9
1000 (92.9 sq m) 0.8
*** For roof slopes greater than 80o,
use Cp = 0.8.
≤
≥
Table 1-8A Windward Roof Pressure Coefficients, Cp , θ < 10o
56. 56
Example 1-3a
The building shown is mostly closed (internal pressure is considered) is used for
an industrial purpose. The building is located in the industrial park situated in the
flat open terrain in Pak Thongchai, Nakhon Ratchasima. Determine the wind load
acting on the walls, sides and roofs following the guidelines given by
ANSI/ASCE 7-95, and draw diagrams of the possible loading calculated.
wind
30 m
15 m
6.5 m
140 km/h
15o
58. 58
6.5 m
7.5 m 7.5 m
15o
h = 6.5 + (7.5tan15o )/2 = 7.5 m
qz = 0.613 KzKztV 2I (N/m2)
• Find qz and qh
)
6060
1
)(
10140
(
3
s
h
h
m
V
×
×
= = 38.89 m/s, I = 1.0 and Kzt = 1 for flat terrain. Therefore,
qz = 0.613 Kz(1)(38.89)2(1) = 927Kz ----------(1)
60. 60
• Find Cp and G
- Windward wall, leeward wall and side walls find from table 1-7.Leeward roof find
from table 1-9 and windward roof find from graph 1-3.See in the reference in the
back.
Cp = 0.5Cp = 0.8
Cp = 0.5
15o
Cp = 0.7
L/B = 15/30 = 0.5
B
L
ridge
plan
Cp = 0.8 Cp = 0.5
Cp = 0.7
Cp = 0.7
63. 63
Example 1-3b
The building shown in the figure is used for industrial purpose and is located
outside of Nakhon Ratchasima, Thailand on flat terrain. When the wind is
directed as shown, determine the design wind pressure acting on the roof and
sides of the building using the ANSI / ASCE 7-95 Specifications. Use G = 0.85.
wind
30 m
15 m
6 m
150 km/h
9 m
64. 64
wind
30 m 15 m
6 m
150 km/h
9 m
qz = 0.613 KzKztV 2I (N/m2)
The basic wind speed is V = 150 km/h = 41.67 m/s , and since the building is used
for industrial purposes, the importance factor is I = 1.0. Also, for flat terrain,
Kzt = 1. Therefore,
qz = 0.613 Kz(1)(41.67)2(1.0)
= 1064 Kz N/m2
θ = tan-1(3/7.5) = 22o, the mean height of the roof is h = 6 + 3/2 = 7.5
θ h
73. 73
251 N/m2
248N/m2
334 N/m2
A
127 N/m2
797 N/m2
833 N/m2
612N/m2
698 N/m2
113 N/m2
B
491 N/m2
433 N/m2
469 N/m2
Conclusion
419 N/m2
419 N/m2
248 N/m2
qzGCp
B
L
ridge
plan
783 N/m2
783 N/m2
412 N/m2
qzGCp
B
L
ridge
plan
74. 74
Design Wind Pressure for Signs.
ffz AGCqF =
Here
G = the wind-gust coefficient factor defined previously, 0.85 (typical)
Cf = a force coefficient which depends upon the ratio of the large dimension M of the sign
to the small dimension N. Values are listed in table below
Af = the area of the face of the sign
Force Coefficients for
Above-Ground Solid Signs, Cf.
M/N Cf
<6 1.2
10 1.3
20 1.5
40 1.75
60 1.85
L
B
75. 75
Earthquake Loads
Deformed
configuration
Initial (undeformed)
configuration
V = CsW
Where, V = total lateral force or base shear, W = dead load of the building,
Cs = seismic response coefficient
Cs =
1.2Cv
RT2/3
<
R
2.5Ca
Where, Cv and Ca are the seismic coefficients based on the soil profile, and on the
effective peak velocity-related acceleration (Av) and the effective peak acceleration
(Aa) respectively; R denotes the response modification factor; and T represents the
fundamental period of vibration of the structure.
Ground motion
76. 76
Hydrostatic and Soil Pressure
h
p = γ h
p = γ h
Where, γ = unit weight of the liquid.
Other Natural Loads
Several other types of live loads may also have to be considered in design of
a structure, depending on its location or use. These include the effect of blast,
temperature changes, and differential settlement of the foundation.
77. 77
Structural Design
Reinforced Concrete Structures
1.) 1.4D + 1.7L
2.) 0.75 [1.4D + 1.7L + 1.7W]
3.) 0.9D + 1.3W
4.) 1.4D + 1.7L + 1.7(soil pressure)
5.) 0.75 [1.4D + 1.7(temperature load) + 1.7L]
6.) 1.4(D + temperature load)
Steel Structures
1.) 1.4D
2.) 1.2D + 1.6L + 0.5(roof live load)
3.) 1.2D + 0.5L (or 0.8W) + 1.6(roof live load)
4.) 1.2D + 0.5L + 0.5(roof live load) + 1.3W
5.) 1.2D + 0.5L + 1.5E
6.) 0.9D -1.3W (or 1.5E)
Allowable Stress Design (ASD)
1.) D + L + [roof live load]
2.) D + L + [W or E]
Where, D = Dead load, L = Live load , W = Wind load , E = Earthquake load
