ce-252need of structural analysis
DESCRIPTION
structural analysisTRANSCRIPT
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Need of structural analysis
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Dr. Ashok K. JainProfessor of Civil Engineering
Indian Institute of Technology Roorkee
Jan 2010
Conceptual Structural System
STRUCTURE
EXCITATION RESPONSE
pv
EXCITATIONLoads
VibrationsSettlements
Thermal Changes
RESPONSEDisplacements
StrainsStress
Stress Resultants
Conceptual Structural SystemConceptual Structural System
EXCITATION RESPONSE
STRUCTURE
EXCITATION RESPONSEpv
Static Dynamic
Static Dynamic
Elastic Inelastic Elastic
Inelastic Linear
Nonlinear Linear
Nonlinear
This process of determining the response of a structure to the given
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excitation is known as structural analysis
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The study of solid mechanics helps in determining whether the material will be able to bear the different types of
stresses and strains
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This also depends upon the shape and size of the
structural element.
structural analysis
Why should I learn it ?
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Among all the civil engineering subjectsStructural engineering is the most difficult
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Among all the structural engineering analysis and design subjects,
Analysis subjects are the most difficultAnalysis subjects are the most difficult
Very difficultHighly mathematicalToo many calculations with too many chances of
structural analysis
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Too many calculations with too many chances of making mistakesToo monotonous
I am already afraid of STATICS
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Can I skip structural engineering subjects all together and still
become a civil i ?
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engineer ?
I put great amount of efforts in learning structural engineering subjectsStillI l k d
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I secure less marks as compared to the efforts put in other subjects
I know little of the structural analysis,So can I jump directly to
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j p ydesign ?
I have decided to go for IT job.
Do I still need to know Structural Engineering
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Structural Engineering ?
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How does it matter ?
If the forces are incorrectIf the nature of the forces is incorrectThat is
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Axial tension or compressionSagging or hogging bending moment
How does it matter ?
If the nature of stresses is incorrect tension or compressionIf there is confusion between normal
d h t
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and shear stress
How does it matter ?
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After all, Civil Engineers are known to work with a
big factor of safety
Myth
Factor of safety is meant to take care of Calculation errorsModeling errors
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gBad materials
Poor construction
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What is Civil Engineering ?
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Pure common sense
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Planning, design, execution and maintenance
of I f t t
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Infrastructure
Can you think of a facility which doesnt need
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c does t eedthe assistance of a civil engineer
?
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A structure
Must transfer all the loads ti it
GOAL
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acting on it safely to the soil below
Even in distress
Please Remember
A Civil Engineer, more specifically,
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p ya structural engineer
is responsible for the safety of lives of hundreds of people
Let us understand what is
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structural design ?
What do you mean by design ?
Creative
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Synthesis No Unique Solution/Open Ended Problem Collaboration in a Team
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What do you mean by design ?
Select appropriate materials Sh d i ( ti ) f b
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Shape and size (proportions) of membersDetailing of members and jointsDoes it satisfy functional requirements economically ?
A design must satisfy
Functional requirements - efficiencySafety against all loads, settlements, temperature fluctuations etc.Time effects and environmental impact
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Innovative
Time effects and environmental impactMust satisfy codal specificationsAestheticsFlexibility to meet future requirementsEconomical w.r.to time and money
Design Process
SYNTHESISANALYSIS
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PERFORMANCE ASSESSMENT
It is very difficult to satisfy so many design constraints
In view of limitations of material strength ductility
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material strength, ductilityand of course cost
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A large number of readymade software are now available in the marketwith very beautiful and powerful
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graphic interfaces.
Do I still have to learn analysis and strain myself?
many structures are known to have failed due to misuse
of the readymade packages
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Liability lies entirely with the designers
A good Designer has to be a good Analyst
However, A good Analyst may not be a good Designer
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good Designer
common sense is a must
A good Analyst has to begood in mathematics
Must be very careful with the sign convention
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Must be comfortable inlatest analytical tools
gincluding axes system
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Let us understand what is
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structural analysis ?
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Bending moment bending stressShear force shear stressAxial force axial stressin ario s members besides displacements
Analysis provides
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in various members besides displacements and rotations
Now design process is routine
To determine the relations betweenLoads applied on a body and the resulting deflections /deformationsLoads applied on a body and the
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Loads applied on a body and the resulting stresses
Stresses and strains for a wide variety of conditions and materials
You may use approximate methods to determine member forces
and their nature
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and their nature
for the understanding of structural analysis
Prerequisite
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Must know how tocompute support reactions in
simple beams and frames H = 0, V = 0, M = 0
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for the understanding of structural analysis
Prerequisite
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Must know how todraw free body diagrams
Free body diagrams
Cut a part of the structure that is of interest.Mark all the loads and internal member forces acting on the free body.
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Assume any direction for the internal forces. The correct direction will be known by satisfying the equations of equilibrium for the free body.
Free body diagram
Determinate Structures : Strength of Materials and Structural Analysis
S ti 11 5 T E 11 3 11 4 B E 12 11
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Section 11.5, Truss: Ex. 11.3, 11.4, Beam: Ex. 12.11, 12.13, 12.16,
Frame : Ex. 13.6 to 13.9
Indeterminate Structures : Advanced Structural AnalysisFrame : Ex. 3.11, 3.12, 5.6, 5.9, 7.2, 10.14 and 10.18Beam : Ex 11.3
M t k h t
for the understanding of structural analysis
Prerequisite
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Must know how tocompute and draw bending moment and shear force diagrams in simple
beams and frames
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Tension side
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Compression side
Sign Convention for BM Diagram
The Bending moment diagram is drawn on the tension side of the member. Thi id th f i f iti d
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This avoids the confusion of positive and negative BM.This helps visualize the deflected shape of the member.Moreover, the reinforcement in RCC members is always provided in the tension zone.
for the understanding of structural analysis
Prerequisite
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Must know how tocompute slope and deflection in simple beams and frames
Computing slope and deflection
Area moment theoremsConjugate beam method
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j gUnit load method
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Unit Load Method
Slope or deflection in beams or frames
EIMmdx
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Deflection in truss
EI AEuLF '
Must learn to apply cross-checks on all calculations
and interpretations
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interpretations
Symmetry / Anti symmetry
Let us play with
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form and support conditions
Truss
Pin endedmember
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Basic module
TRIANGLE
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Basic pin element
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Axial ForceCompression
Tension
Roof Truss
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Bridge Truss
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Bridge Truss
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Warren Truss
Warren Truss
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Bridge Truss
Pratt
57Howe
PIN CONNECTIONS RIVETTED OR WELDED
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PIN CONNECTIONS RIVETTED OR WELDED
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Kuala Lumpur Airport, Malaysia
PIN CONNECTIONS RIVETTED OR WELDED
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Terminal 1D Delhi Airport
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PIN CONNECTIONS RIVETTED OR WELDED
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Tokyo Inst Tech - Tokyo
PIN CONNECTIONS RIVETTED OR WELDED
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PIN CONNECTIONS RIVETTED OR WELDED
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Pin ended column
Basic beam elementor
column element
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Axial ForceShear Force
Bending moment
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Statically determinate beams
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u = 0v = 0 = 0
u 0v = 0 0
u = 0v = 0 0
Continuous beams
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0
Arch
ParabolaEllipse
Any other
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Frames
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1
4
1
Frames
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u = 0v = 0 0
u 0v = 0 0
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Frames
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Frames
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Loads
Static loadsDynamic loadsCyclic loads
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Deterministic loadsNon-deterministic loads
Loads
Concentrated loadUniformly distributed loadCouple or Bending moment
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Dead loadImposed loadLateral load
Permutation andCombinations
of
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FormSupport conditions
Loads
Sky is the limit
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Thank you
Suvarnabhumi Airport, Bangkok
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Ravana
Suvarnabhumi Airport, Bangkok
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Suvarnabhumi Airport, Bangkok
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Suvarnabhumi Airport, Bangkok
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Suvarnabhumi Airport, Bangkok
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Suvarnabhumi Airport, Bangkok
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