STRUCTURAL ANALYSIS
(Determinate)
Soran University
Faculty of Engineering
Civil Engineering Department
Yousif J. Bas
(2023-2024)
CHAPTER 1
Types of Structures
and Loads
Types of Structures and Loads
CHAPTER OBJECTIVES
 To introduce the basic types of structures.
 To provide a brief explanation of the various types
of loads that must be considered for an appropriate
analysis and design.
R. C. Hibbeler, Structural Analysis, 10th Edition, 2017
(Yousif J. Bas)
Chapter Outline
 Introduction
 Classification of Structures
 Loads
 Structural Design
Introduction
 A structure refers to a system of connected parts used to
support a load.
 Important examples related to civil engineering include
buildings, bridges, and towers.
 in other branches of engineering, ship and aircraft frames,
tanks, pressure vessels, mechanical systems, and electrical
supporting structures are important.
 When designing a structure factors to consider:
 Safety
 Esthetics
 Serviceability
 Economic & environmental constraints
Classification of Structures
 Structural elements
 Tie rods
 Beams
 Columns
Classification of Structures
 Structural elements
Classification of Structures
 Structural elements
Classification of Structures
 Types of structures
 Trusses
 Cables & Arches
 Frames
 Surface Structures
Classification of Structures
 Types of structures
Loads
Loads
Structural forms
Elements carrying primary loads
Various supporting members
Foundation
Loads
 Design loading for a structure is often specified in codes
 General building codes
 Design codes
Loads
Types of load
 Dead load
 Weights of various structural members
 Weights of any objects that are attached to the structure
Loads
Example
The floor beam is used to support
the 1.8 m width of lightweight plain
concrete slab having a thickness of
100mm. The slab serves as a portion
of the ceiling for the floor below &
its bottom coated with plaster. A 3 m
high, 300mm thick lightweight solid
concrete block wall is directly over
the top flange of the beam.
Determine the loading on the beam
measured per m length of the beam.
Loads
Solution
Using the data provided from the table,
concrete slab : (0.015kN / m 2 .mm)(100mm)(1.8m)  2.70kN / m
plaster ceiling : (0.24kN / m 2 )(1.8m)  0.43kN / m
block wall : (16.5kN / m 3 )(3m)(0.3m)  14.85kN / m
Total  2.70  0.43  14.85  17.98kN / m
Loads
 Live loads
 Varies in magnitude & location
 Building loads
 Depends on the purpose for which the building is designed
 These loadings are generally tabulated in local, state or national
code
Loads
 Highway Bridge loads
 Primary live loads are those due to traffic
 Specifications for truck loadings are reported in American
Association of State and Highway Transportation Officials
(AASHTO)
Loads
 Railway Bridge loads
 Loadings are specified in American Railway Engineering and
Maintenance-of-Way Association (AREMA)
Loads
 Impact loads
 Due to moving vehicles
 The % increase of the live loads due to impact is called the
impact factor, I
 This factor is generally obtained from formulas developed from
experimental evidence. For example, for highway bridges the
AASHTO specifications require that
Loads
 Wind loads
 Kinetic energy of the wind is converted into
potential energy of pressure when structures block the flow of wind
 Effect of win depends on density & flow of air, angle
of incidence, shape & stiffness of the structure & roughness of
surface
 For design, wind loadings can be treated using static or dynamic
approach
Loads
 Wind loads
q z  0.613K z K zt K K eV 2 ( N / m 2 )
d
where
V  velocity in m/s of a 3s gust of wind measured 10m above the ground.
Values are obtained from a wind map.
K z  the velocity pressure exposure coefficient. A function of height and depends upon the ground terrain.
See Table 1.5.
K zt  a topographic factor that accounts for wind speed increases due to hills % escarpments. For flat ground K zt  1
K d  a factor that accounts for the direction of the wind.
It is used only when the structure is subjected to combination of loads.
For wind acting alone, K d  1
K e  a ground elevation factor; for a conservative design use K e  1
Loads
 Wind loads
 Once qz is obtained, the design pressure can be obtained from a list
of relevant equations
p  qGCp  qh (GC pi )
q  q z for the windward wall at height z above the ground
q h for the leeward wall where z  h , mean height of the roof
G  a wind - gust effect factor, depending on exposure.
For a rigid structure, G  0.85
C p  wall or roof pressure coefficient
Negative values indicate pressure acting away from the surface.
GC pi  the internal pressure coefficient which depends upon the
type of openings in the building.
For fully enclosed building, GC pi  0.18
Loads
 Snow loads
 Design loadings depend on building’s general shape & roof
geometry, wind exposure, location, its importance and whether or
not it is heated
 Snow loads are determined from a zone map reporting 50-year
recurrence intervals of an extreme snow depth
Loads
 Snow loads
 For flat roof (slope < 5%):
p f  0.7C e C t I s p g
(eq 1.5)
C e  an exposure factor depending upon the terrain.
A fully exposed roof in an unobstructed area C e  0.8.
If the roof is sheltered & located in the centre of a large city C e  1.2
C t  a thermal factor which refers to the average temperature
within the building. For unheated structure kept below freezing
C t  1.2, whereas if the roof is supporting a normally heated structure, then C t  1.0.
I  the importance factor as it relates to occupancy.
For e.g, I  0.8 for agriculture & storage facilities and I  1.2 for schools & hospital
Loads
 Earthquake loads
 Earthquakes produce lateral loadings on a structure
through the structure’s interaction with the ground.
 Their magnitude depends on amount
& type of ground acceleration, mass &
stiffness of structure
 The block is the lumped mass
of the roof
 the column has a total stiffness
representing all the building’s
columns
 During earthquake,
the ground vibrates
both horizontally & vertically
Loads
 Earthquake loads
 The effects of a structure’s response can be determined &
represented as an earthquake response spectrum
 For small structures, static analysis is satisfactory
S DS
Cs 
R / Ie
S DS  spectral response acceleration for short periods of vibration
R  response modification factor that depends upon the ductility of the structure
I  importance factor that depends on the use of the building
Loads
 Hydrostatic & Soil Pressure
 The pressure developed by these loadings when the structures are
used to retain water or soil or granular materials
 E.g. tanks, dams, ships, bulkheads & retaining walls




Other natural loads
Effect of blast
Temperature changes
Differential settlement of foundation
Structural Design
 Whenever a structure is designed, it is important to give
consideration to both material and load uncertainties. These
uncertainties include:
1.
2.
3.
4.
5.
A possible variability in material properties
residual stress in materials
intended measurements being different from fabricated sizes
Loadings due to vibration or impact
material corrosion or decay
Structural Design
 ASD. Allowable-stress design (ASD) methods include both the
material and load uncertainties into a single factor of safety.
 The many types of loads discussed previously can occur
simultaneously on a structure, but it is very unlikely that the
maximum of all these loads will occur at the same time. For
example, both maximum wind and earthquake loads will normally
not act simultaneously on a structure.
 In working-stress design, the computed elastic stress in the material
must not exceed the allowable stress along with the following
typical load combinations as specified by the ASCE 7-16 Standard
 dead load
 dead load + live load
 0.6 (dead load) + 0.6(wind load)
Structural Design
 LRFD. (load and resistance factor design)
Since uncertainty can be considered using probability theory, there
has been an increasing trend to separate material uncertainty from
load uncertainty.
 this method (LRFD) or (strength design) uses load factors applied
to the loads or combinations of loads
 1.4 (Dead load)
 1.2 (dead load) + 1.6 (live load) + 0.5 (roof live load or snow load
or rain load)
 1.2 (dead load) + 1.0 (wind load) + 1.0 (live load) + 0.5 (roof live
load or snow load or rain load)
 0.9 (dead load) + 1.0 (wind load)