Structural Integrity Analysis. Chapter 1 Stress Concentration
structural analysis Chapter 1
-
Upload
mohammad-khawam -
Category
Engineering
-
view
147 -
download
12
Transcript of structural analysis Chapter 1
![Page 1: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/1.jpg)
1
Chapter 1: Types of structures and loads
Introduction
Fundamental of Structural Theory
Classification
Loads
Structural design
![Page 2: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/2.jpg)
2
Introduction
A structure refers to a system of connected parts used to support a
load....
Structure
Design of structures
Safety
Esthetics
Serviceability
Environment
Economy
Analysis of structures
Strength
Rigidity
Idealization of structures
Physical model
Mathematical model
![Page 3: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/3.jpg)
3
Fundamental of structural theory
![Page 4: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/4.jpg)
4
![Page 5: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/5.jpg)
5
Classification of structures
Structural Elements
Tie rods: Structural members subjected to a tensile force are
often referred to as tie rods or bracing struts.
![Page 6: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/6.jpg)
6
Beams: are usually straight horizontal members used primarily
to carry vertical loads.
![Page 7: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/7.jpg)
7
Columns: Members that are generally vertical and resist axial
compressive loads are referred to as columns.
![Page 8: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/8.jpg)
8
Types of structures
Trusses:
Cables and arches:
![Page 9: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/9.jpg)
9
Frames: Frames are often used in buildings and are composed
of beams and columns that are either pin or fixed connected.
Surface structures: A surface structure is made from a
material having a very small thickness compared to its other
dimensions.
![Page 10: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/10.jpg)
10
Loads
The design loading for a structure is often specified in codes.
![Page 11: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/11.jpg)
11
![Page 12: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/12.jpg)
12
Dead loads:
Dead load consist of the weights of the various structural
members and the weights of any objects that are
permanently attached to the structure.
The densities of typical materials used in construction are
listed in Table 1-2, and a portion of a table listing the
weights of typical building components is given in table 1-
3.
![Page 13: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/13.jpg)
13
![Page 14: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/14.jpg)
14
![Page 15: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/15.jpg)
15Dead load = 4.72 + 0.48 + 12.375 = 17.575 KN/m
Example: The floor beam is used to support
the 2m width of a lightweight plain concrete slabhaving 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.
Furthermore, a 2.5m height, 30 cm thick light
weight solid concrete block wall is directly over
the top flange of the beam. Determine the loading
on the beam measured per meter of length of the
beam.
0.24
16.5 12.375 kN
0.48 kN
Solution
See tables
![Page 16: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/16.jpg)
16
![Page 17: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/17.jpg)
17
![Page 18: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/18.jpg)
18
Live loads:
Live loads can vary both in their magnitude and location.
They may be caused by the weights of objects temporally
placed on a structure, moving vehicles, or natural forces.
Various types of live loads will now be discussed.
![Page 19: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/19.jpg)
19
![Page 20: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/20.jpg)
20
For some types of buildings having very large floor areas, many codes will
allow a reduction in the uniform live load for a floor, since it is unlikely that the
prescribed live load will occur simultaneously throughout the entire structure
at any one time.
(37.2) square meters, equal to four
0
57.425.0 L
AL
I
0
1525.0 L
AL
I
(FPS units)
(SI units)
![Page 21: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/21.jpg)
21
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.
Problem 1-2
![Page 22: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/22.jpg)
22
SOLUTION: ANSI-based US Code
The roof loading is 100 kg/m2 (given)
At = (7 m)(7 m) = 49 m2
FRoof = (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,
250494
57.425.0
4
57.425.0
57.425.0 00
L
AL
AL
tI
2/144250575.0 mkgL
The load reduction = (0.575)L0 > (0.50)L0 O.K. Therefore,
FFloor = (144 kg/m2) (49m2) = 7.044 t
Floor:
Roof:
![Page 23: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/23.jpg)
23
Ground floor:
For the ground floor, the live load is taken from table 1- 4:
Lo = 250 kg/m2 . No live load reduction is allowed.
FGround floor = (250 kg/m2)(49 m2) = 12.25 T
The total live load supported by the foundation is thus
F = FRoof + FFloor + FGround floor = 4.90 + 7.044 + 12.25 = 24.19 T
![Page 24: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/24.jpg)
24
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.
![Page 25: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/25.jpg)
25
SOLUTION
For the US code based on ANSI:
At = (7 m)(7 m) = 49 m2
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,
250494
57.425.0
4
57.425.0
57.425.0 00
L
AL
AL
tI
2/144250575.0 mkgL
The load reduction here is (0.575)L0 > (0.40)L0 O.K. Therefore use 0.575 for all.
![Page 26: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/26.jpg)
26
![Page 27: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/27.jpg)
27
Bridge Loads
12 ton truck 21 ton truck
For highway c the Association of State and Highway Transportation Officials
(ASHTO) Specification gives the expression for the impact factor (I) 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.
3.01.38
24.15
LI
![Page 28: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/28.jpg)
28
Wind Loads
Wind Pressure for Building
External Pressure
Internal Pressure
![Page 29: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/29.jpg)
29
External Pressure
![Page 30: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/30.jpg)
30
External Pressure: Formulation
p = q G C
Where, q = basic pressure at the height of 10 m
q = 0.613 KzKztKdV 2I With (q [N/m2], V [m/s])
V: the velocity of a 3 seconds gust of wind measured 10m above the
ground during a 50-year recurrence period. Values are obtained from a
wind map shown in figure 1-12.
I: the importance factor that depends upon the nature of the building
occupancy; for example, for buildings with a low hazard to human life,
such as agriculture facilities in a non-hurricane prone region, I = 0.87,
but for hospitals, I = 1.15
Kz: The velocity pressure exposure coefficient, which is a function of
height and depends upon the ground terrain. Table 1- 5 lists values for
a structure which is located in open terrain with scattered low-lying
obstructions
Kzt: a factor that accounts for wind speed increases due to hills and
escarpments, for flat ground Kzt = 1.
Kd: a factor that accounts for the direction of the wind. It is used
only when the structure is subjected to combinations of loads. For
wind acting alone, Kd = 1.
![Page 31: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/31.jpg)
31
p = wind pressure
G = gust factor (0.85, typical)
C = shape factor
p = q G C
![Page 32: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/32.jpg)
32
External Pressure on Main Wind-Resisting System
q = 0.613 KzKzt KdV 2I With (q [N/m2], V [m/s])
p = q G Cp
Cp: a wall or roof pressure coefficient (see Figures below).
qz: windward wall.
qh: Leeward wall.
![Page 33: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/33.jpg)
33Cp: See figure 1-13 (textbook)
![Page 34: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/34.jpg)
34
Internal Pressure: Enclosed Building*
Internal Pressure: Partially Open Building*
* Reference: ASCE 7-98
![Page 35: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/35.jpg)
35
![Page 36: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/36.jpg)
36
![Page 37: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/37.jpg)
37
![Page 38: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/38.jpg)
38
![Page 39: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/39.jpg)
39
![Page 40: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/40.jpg)
40
![Page 41: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/41.jpg)
41
![Page 42: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/42.jpg)
42
![Page 43: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/43.jpg)
43
![Page 44: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/44.jpg)
44
![Page 45: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/45.jpg)
45
Wall pressure coefficient, Cp.
![Page 46: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/46.jpg)
46
Maximum negative roof pressure coefficient, Cp, for use with qh.
![Page 47: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/47.jpg)
47
![Page 48: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/48.jpg)
48
![Page 49: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/49.jpg)
49
![Page 50: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/50.jpg)
50
![Page 51: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/51.jpg)
51
![Page 52: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/52.jpg)
Design Wind Pressure for Signs.
Here:F= qzGCfAf
If a structure is classified such that, the distance from
the ground to the bottom edge must be equal to or
greater than 0.25 times the vertical dimension, the wnd
will produce a resultant force acting on the face of the
sign which is determined from:
52
![Page 53: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/53.jpg)
Hydrostatic and Soil Pressure
53
![Page 54: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/54.jpg)
54
Snow loads:Like wind, snow loads in the ASCE 7-02 Standard are generally determined
from a zone map reporting 50-year recurrence intervals of an extreme snow
depth.
If a roof is flat, defined as having a slope of less than 5%, then the pressure
loading on the roof can be obtained by modifying the ground snow loading,
pg, by the following empirical formula:
Pf = 0.7CeCtIpg
Here:
Ce: exposure factor which depend upon the terrain. For example, for a fully
exposed roof in an unobstructed area, Ce = 0.8, whereas if the roof is
sheltered and located in the center of a large city, then Ce = 1.3
Ct: a thermal factor which refers to the average temperature within the
building. For unheated structures kept below freezing Ct =1.2, whereas if the
roof is supporting a normally heated structure, then Ct = 1.0.
I: the importance factor as it relates to occupancy. For example, I = 0.8 for
agriculture and storage facilities, and I = 1.2 for hospitals.
![Page 55: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/55.jpg)
55
If pg ≤ 20lb/ft2 (0.96 kN/m2), then use the largest value for pf, either computed
from the above equation or from pf = Ipg.
If pg > 20lb/ft2 (0.96 kN/m2), then use pf =I(20lb/ft2).
![Page 56: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/56.jpg)
56
![Page 57: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/57.jpg)
57
![Page 58: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/58.jpg)
58
Structural Design
Reinforced Concrete Structures
Steel Structures
![Page 59: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/59.jpg)
59
![Page 60: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/60.jpg)
60
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.
![Page 61: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/61.jpg)
61
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,
![Page 62: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/62.jpg)
62
![Page 63: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/63.jpg)
63
![Page 64: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/64.jpg)
64
![Page 65: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/65.jpg)
65
![Page 66: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/66.jpg)
66
![Page 67: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/67.jpg)
67
![Page 68: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/68.jpg)
68
![Page 69: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/69.jpg)
69
![Page 70: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/70.jpg)
70
![Page 71: structural analysis Chapter 1](https://reader033.fdocuments.in/reader033/viewer/2022042522/55a5b2b51a28aba07b8b4655/html5/thumbnails/71.jpg)
71