Intro to Structural Engineering

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Haward Technology Middle East
PIONEERS IN TECHNOLOGY TRANSFER
Mr. Jorge Palma
Structural Engineering for
Non-Structural Engineers

Haward Technology Middle East 2
Section 1
Section 1
Introduction to Structural
Engineering
The Structural Engineer Role
Governing Principles
Overall Course Objective

Section 1
 Structural Engineering deals with the analysis and
design of structures.
 Structure can be defined as an assembly of various
components that act together under “stress”
conditions.
 Bridges, highways, buildings, transmission towers,
trusses, water tanks, offshore structrures, are common
today.

Section 1
 The basic purpose of designing a structure is to ensure
its safety, functionality and economy under the most
severe condition of using, during its lifespan.
• Information flows of studies and research increasing
• Improvements of manufacturing process and
materials
• Fast upgrade of design tools (including CAD
software)
• Engineering applications are interdisciplinary
(Architecture, Construction, Maintenance,
Repairing, Financing, Environmental…)

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The Structural Engineer Role: The Design
 Optimal structural design shall achieve balance
between the following requirements:

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Governing Principles Of Engineering Design
 Application of basic scientific principles for safe,
practical and cost effective solutions.
 Strutuctural design is based on:
• Mechanics (analyzes structural components as rigid
bodies under external actions)
• Strengh of materials (analyses structural
components as deformable bodies under external
action depending of material properties)

Section 1
Overall Course Objective
 Identify the role of structural engineer
 Explain the behavior of structural members under
loading
 Apply the concept of stress functions like tension,
compression, shear and bending
 Use the basic concepts for analysis of statically
determinate and indeterminate structures
 Analyze deformation of members under loading
 Discuss the significance of material properties in design
 Perform basic design of reinforced cement concrete
structures, steel structures and masonry & timber
structural members

Section 1
Principles of Strength of Material
 Theory of Elasticity Objectives:
• Understand the mechanical properties of the
material
• Undesrtand the behavior of the material under
stress.
• Understand the mechanism of deformation of
material and evaluate the magnitudes

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 Mechanical properties
• Properties related to strees and deformations are
important for structural engineering and
construction
• They are determined in laboratory conditions to
establish permissible limits.

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 Elasticity of materials
• All material bodies undergo deformations when
loads are applied on them.
• When the applied load is removed, body does
overcome this deformation and recovers original
shape.
• This property is know as elasticity

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Elasticity of Materials Stress
and Strain
 When a prismatic member
is applied on a load along
its axis, the load is
uniformly distributed along
its entire cross sectional
area (tension)

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Elasticity of materials
 Force per unit area = F/A= σ
 Stress (kgf /cm2
, or N/mm2
)
 Elongation per unit area: ∆l/l= ε
 Strain (unitless quantity)

Section 1
Hooke’s Law:
 “Within elastic limits, strain is proportional to stress”
σ= ε x E
 Where E is the modulus of Elasticity or Young´s
Modulus

Section 1
Hooke´s Law

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Poisson´s Ratio:
 Lateral strain /axial strain = µ (constant)
 For isotropic materials its value is 0,25
 Change in volume per unit of volume
∆V/V= ε(1-2µ)
 Limit value of µ can be: µ= 0.5
 For metals: µ= 0.25-0.35

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 Young´s Modulus helps to evaluate deformation of
material under stress and Poisson´s ratio allows to
understand the ofailure mechanism of various strutural
materials.

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Oblique Section

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Oblique Section. Normal Stress

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Oblique Section. Tangential Stress
 Many materials have lower resistance to shear than to
axial forces.

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Flexural Stresses in Beams

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Flexural Stresses in Beams (Pure Bending(

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Flexural Stresses in Beams (Pure Bending(
Stress, σmax=(M/z)
 This expression of relationship between maximum
bending stress, moment at the section and the
sectional property Z ,called section Modulus.
 (Section Modulus depends to the Moment Inertia I and
the farthermost layer from the centroidal axis.)

Section 1
Flexural Stresses in Beams. Moment Inertias.

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Principles of Strengh of Material
Principles of Bending Stress Applied

Section 1

Section 1
Shear Forces and Bending Moment

Section 1
Shear Forces and Bending Moment
 For first and second cases i and ii, (without UDL=w),
the rate of change of the bending moment will be:
 For second case ii (considering all vertical forces), the
rate of change of shear forces is:

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 For case iii (only concentrated load W), the rate of
change of the shear force will be sudden , then dM/dx
would become discountinuos at the section of
application of the load.

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 Bending Shear
Stress in sections
reach maximum
along neutral axis
interfaces

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Bending Shear Stress
 Horizontal and vertical shear stress. Relationships:
τ (h) = τ (v)

Section 1
Bending Shear Stress

Section 1

Section 1
Bending Shear Stress. Determination. Distribution
of Flexural Stress

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Bending Shear Stress. Determination. Distribution of
Flexural Stress
 Static Moment of beam Area respect to the neutral
axis. For rectangular beam the static moment area is:

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of Flexural Stress

Section 1
of Flexural Stress
Determination of maximum value of W

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Flexural Stress

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Flexural Stress
 Determination of maximum value of W

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of Flexural Stress
 Determination of maximum value of W
The permissible value of the load derived from the
criteria of bending stresses in much smaller compared
to a smilar value derived from the criteria of shear
stress. Therefore it is clear that maximum bending
stress shall goven the design in the case and the
maximum permissible value of W shell be 18,000 N.

Section 1
Deformation of Beams
 The design of beams also may be determined by its
resistance to deformation, a property termed as rigidity.
 Deformation should be within acceptable limits.
 Deflection is one of the most critical measurements of
deformation.
 Due to loads on beam and the moment generation at the
section the beam adopts a new profile know as:
deflected shape of the beam.
 We are limited to elastic deformation only and consider
that stress is proportional to straim ( Hook´s law).

Section 1
Deformation of Beams. Elastic Curve

Section 1
Deformation of Beams. Elastic Curve
Maximum deflection

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Deformation of Beams. Elastic Curve. Moment Area
Method

Section 1
Deformation of Beams. Moment Area Method
 Theorem –I: For an elastic curve, the angle between
tangents at any two points on the curve is equivalent
to the total area of the bending moment diagram
between these two points, divided by EI.
 Theorem –II: for an elastic curve, the deviation of any
point prependicular to the original beam axis, relative
to the tangent drawn on the curve at any other point,
is equivalent to the moment of the area of the bending
moment about the first point, divided by EI.

Section 1

Section 1
Combined Stresses, Bending and Compression

Section 1
Combined Stresses, Bending and Compression
 For topmost layer, the direct compressive stress shall neutralize
the value of the tensile flexure stress-assuming flexural one is
larger. The net tensile stress:
 For bottom most layer, the direct compressive stress shall add to
the value of the tensile flexure stress. The net compressive
stress at the bottommost layer:

Section 1
Combined Stresses in Columns (along x-x´(

Section 1
Combined Stresses in Columns (along x-x´(
 Due to combined effect of the moment a direct force,
the stresses on the outermost fibers will be:
 As W/A is the compressive stress, the use of positive
sign will give the value of maximum compressive
stress and the use of negative sign will give the value
of the maximum tensile stress.

Section 1
Lateral Deformation of Columns. Euler´s Formula.
 In long colums, the flexural stress - or buckling -
governs the failure
 The importance of direct compressive stress is
relatively low.
 It is not possible to determine the rate of change of
flexural stress with the change in the magnitude of the
direct stress.

Section 1

Section 1
(hinged ends(

Section 1
Principles of Strength of Material.
End Conditions and Critical Loads

Section 1
Conclusions
 Exposed principles of strength of materials give us and
idea about the behavior of materials under stress.
 We can appreciate the reason of behaviors, that are
important from the point of view of structural
engineering in relation to material properties.
 Internal stresses develop depending on load conditions
and stress function like bending and shear originates
from similar loading.
 The deformation of structures depends on stress and
several factors different from material. Column
members have special analysis for deformations

Section 1
Structural Analysis
Principle of Mechanics
Objectives:
 Understand the types of structures and their
components
 Understand the different types of stresses and the way
strutural arrangements offer resistance to them
 Gain knowledge about the types of load and nature of
stresses and deformation that they can induce.
 Understand the principles of mechanics and their
applications in structura analysis
 Use the analytical tools to analyze the statically
determinate structures

Section 1
Structural Analysis
 The function of structures has been to withstand
stresses due to self-loads, direct loads and restrains
imposed on phisycal characteristics –like changes in
dimensions with temperature.
 Steps in typical design are:
• Study the loads and constrains under the situations
• Propose a suitable strutural system
• Examine the overall stability of the same
• Calculate internal forces and deformation of the
members
• Modify and fine tune overall dimensions and sections
of the members.

Section 1
Structural Analysis
 Clasification of structures may be by:
• Purposes (buildings for habitation, sheds for
factory, bridges for transportation, dams for water
retention, chimneys, aeroports, ports
telecomunications towers…)
• Shape and forms (beams, columns, slabs, walls,
footings, frames, trusses)
• Analytical procedure ( determinate and
indeterminate structures, two-dimensional, tri-
dimensional

Section 1
Structural Analysis
 Types of loads:
• Dead loads
• Live loads
• Lateral loads
• Snow loads
• Thermal loads
• Other

Section 1
Structural Analysis
Loads

Section 1
Structural Analysis
Principle of Mechanics. Loads
Live Load

Section 1
Structural Analysis
Loads

Section 1
Structural Analysis

Section 1
Structural Analysis
Loads

Section 1
Structural Analysis

Section 1
Structural Analysis
http://youtu.be/j-zczJXSxnw

Section 1
Structural Analysis

Section 1
Structural Analysis
 Unexpected Extreme Loads: Sendai, Japan 8.9 Earthquake and 7.0
m. Tsunami wave

Section 1
Structural Analysis
 Unexpected Extreme Loads: Sendai, Japan 8.9
Earthquake and 7.0 m. Tsunami wave
http://vimeo.com/21769477

Section 1
Structural Analysis
 Structures falling
• http://youtu.be/uKeENdyIluI
• http://youtu.be/GtIjUn7_erY
• http://youtu.be/INmYGiJHgTs

Section 1
Structural Analysis

Intro to Structural Engineering

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