PMCE Structural Dynamics
Transcript of PMCE Structural Dynamics
CE 809 - Structural Dynamics
Lecture 0: Course Introduction
Semester – Fall 2021
Dr. Fawad A. Najam
Department of Structural Engineering
NUST Institute of Civil Engineering (NICE)
National University of Sciences and Technology (NUST)
H-12 Islamabad, Pakistan
Cell: 92-334-5192533, Email: [email protected]
Prof. Dr. Pennung Warnitchai
Head, Department of Civil and Infrastructure Engineering
School of Engineering and Technology (SET)
Asian Institute of Technology (AIT)
Bangkok, Thailand
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Examples of Problems related to Structural Dynamics
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Tacoma Narrows bridge
• A classic example.
• A suspension bridge built in 1940s.
• The bridge was designed by one of the leading experts in suspension bridges at that time.
• Dead load, traffic load, and wind induced drag load (lateral force) were considered in the structural
design.
• However, the bridge collapsed during a wind storm in which the wind velocity was much lower than
the maximum wind speed used in the design.
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Flutter of Tacoma Narrows Bridge
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Tacoma Narrows bridge
• The design, based on static concept, was perfectly correct, but the dynamic effects were not
considered.
• From the recorded motion picture, we found that the bridge collapsed by a certain unstable dynamic
excitation mechanism (torsional flutter).
• Starting from small amplitude torsional oscillation, the motion grew up until suspended ropes broke
by fatigue, and then the bridge collapsed.
• After this failure, many studies on bridge dynamics were conducted, and every bridge engineer who
involves in the design of long-span bridges has to learn the theory of structural dynamics.
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Flutter of Tacoma Narrows Bridge
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Wind Effects on Structures
Static
effects
Deformation due to time-averaged aerodynamic force
Stress due to wind-induced pressure or force
Static
instability
Torsional divergence (negative stiffness)
Lateral buckling
Dynamic
effects
Forced
vibration
Buffeting (random
vibration)
due to atmospheric turbulenceLimited-
amplitude
response
due to body-induced turbulence (wake)
Vortex excitation
Dynamic
instability
(negative
damping)
Galloping
Divergent-
amplitude
response
Wake galloping
Torsional flutter
Coupled flutter
Rain-induced vibration
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A Hospital Building subjected to an earthquake
• Structural safety is the main concern.
• A hospital building was subjected to the San Fernando
earthquake in 1971, and it was severely damaged.
• The building vibrated like a large rigid mass shaking on
flexible columns. These columns had to resist large
cyclic shear force, and after few cycles they failed.
• The dynamic shear force is proportional to the product
of mass and acceleration of the building
𝐹 = 𝑚 𝑎
Olive View Hospital
(First story has a permanent displacement of 2 feet (61 cm)
Courtesy: P. C. Jennings and G. W. Housner
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Earthquake Loading on Structures
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A Hospital Building subjected to an earthquake (continued)
During the 9 February 1971 San Fernando earthquake the new Olive View Hospital building was
severely damaged. In response to very strong ground shaking. the building vibrated essentially as a
large mass on relatively flexible columns. The spirally reinforced concrete columns were deformed
far beyond the requirements of the building code.
Second story column fracture in Olive View Hospital
Collapsed first story of Psychiatric building at
Olive View HospitalOlive View Hospital after February 1971 San
Fernando earthquake
Courtesy: P. C. Jennings and G. W. Housner
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A Hospital Building subjected to an earthquake (continued)
• In many current seismic resistant design codes, a regular building may be designed by a static
method, that is, the building may be designed to resist an equivalent static lateral force (of
earthquake).
• Although the analysis involved is static analysis, the equivalent static force is entirely formulated
from the consideration of the dynamic behavior of the building.
• For the seismic design of complex structures and/or important structures, an explicit dynamic
analysis may be required.
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Wenchuan Earthquake (2008), China
Magnitude = 7.9
Death Toll > 70,000
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Balakot, Kashmir Earthquake (2005)
Magnitude = 7.6
Death Toll = 79,000
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Yogyakarta Earthquake (2006)
Magnitude = 6.2
Death Toll = 5,000
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Kobe Earthquake (1995)
Magnitude = 6.9
Death Toll > 6000
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Earthquake Motion: Kobe Earthquake, 1995
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Typical Commercial Concrete Buildings
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Building Response to EQ Ground Shaking
Lateral-Torsional Movement (period = 0.50 sec)
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First-story Collapse of Commercial Buildings The 1999 Chi-Chi Earthquake (Taiwan)
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Why This Course?
Location of Major Earthquakes in Last 100 Years
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Why This Course?
Seismic zonation of Pakistan as per Building Code of Pakistan (BCP). The areas in red color (Zone 4) are under severe threat of earthquakes.
The areas in dark blue and light blue are relatively less exposed to seismic threat.
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Tower Structures
• Marine observation towers, airport control towers, tall and slender buildings (see the following
slides).
• These structures are safe against wind and earthquake.
• But the wind-induced vibration may causes human discomfort – motion sickness, difficult to perform
desk work, furniture and fixtures make sounds
• Serviceability problems
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The Yokohama Marine
Tower (Japan, 1961)
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The Sydney Tower
(Australia, 1981)
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The CN Tower
(Canada, 1976)
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Tall Buildings - Dynamic Wind Effects need to be considered !
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Photo Courtesy: http://www.bangkok.com/magazine/baiyoke-tower-II.htmPhoto Courtesy: https://www.bangkokpost.com/learning/advanced/1073529/
Tall Buildings - Dynamic Wind Effects need to be considered !
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Response of a mid-rise
building with a high
natural frequency
Response of a high-rise
building with a low natural
frequency
Wind force (Drag)
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A Steel Stack
A Steel Stack
Pendulum Tuned Mass Damper
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Suspended Wire Rope
Steel Ring
Viscous Damper
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A Pedestrian Bridge
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A Pedestrian Bridge
• 2000 pedestrians walk across the bridge in the same time.
• The bridge is subjected to human-induced force in both vertical and horizontal directions.
• The bridge girder vibrates laterally, and the stay cables also vibrate with very large lateral vibration
amplitudes, says up to 50 cm.
• The dynamic stresses are so low that the structure will never fail.
• And the vibrations are too low to cause any difficulty on the walking mode of pedestrians.
• But many pedestrians are afraid to walk. Many people complain about the vibration, and many of
them think that the bridge was poorly designed and constructed.
• Problem of ‘human perception of vibration’
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Why This Course? - Course Objectives
• As modern structures are becoming slender and light, they are also becoming more susceptible to
dynamic loadings.
• Various examples of real-life dynamic problems that frequently confront civil engineers include:
• Aerodynamic stability of long-span bridges
• Earthquake response of multi-story buildings
• Impact of moving vehicles on highway structures, etc.
• The traditional engineering solutions to these problems, based on "static force" and "static response", are
no longer valid in most cases.
• Many of these problems have to be tackled by applying the knowledge of structural dynamics. Thus, a
basic understanding of the dynamic behavior of structures as well as the underlying principles is essential
for structural engineers.
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Learning Outcomes
• Develop the basic understanding of principles of structural dynamics
• Develop the ability to integrate the principles of structural dynamics in structural design of buildings and
structures
• Develop the ability to analyze and solve problems in dynamic response and behavior of buildings and
structures
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Course Outline
1) Dynamics of Simple Structures (single-degree-of-freedom systems)
a. Equation of motion
b. Free vibrations
c. Response to harmonic force
d. Response to periodic force
e. Response to arbitrary dynamic force
f. Nonlinear dynamic response
2) Multi-Degree-Of-Freedom Structures
a. Formulation of matrix equations of motion
b. Analysis of free vibrations
c. Modal analysis and forced vibrations
d. Nonlinear dynamic response
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Course Outline
3) Continuous Structures
a. Partial differential equations of motions (for strings, bars, beams)
b. Modal analysis
c. Wave propagation analysis
4) Earthquake Response
a. Response spectrum concept
b. Application to earthquake engineering
5) Random Vibrations
a. Probability theory, random processes
b. Correlation and spectral density functions
c. Response to stationary random excitations
d. Crossing, peak distributions, extreme value analysis, evaluation of fatigue life
e. Application to wind engineering
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Course Outline
6) Control of Dynamic Response
a. Overview of vibration control
b. Tuned Mass Dampers
c. Active vibration control
Chapter Topic Videos YouTube Link Duration
Introduction Introduction to the Course y2u.be/MCRX1KXQZBU 16:42
Dynamics of
Simple
Structures
SDF Systems Formulation of Mathematical Model of SDF Systems y2u.be/sbxf1D1Umvw 50:53
Free Vibration Free Vibration Response of SDF Systems y2u.be/_ZUp3c5IMIk 1:47:25
Harmonic Loading
Response of SDF Systems to Harmonic Loading - Part 1 y2u.be/qh47IyfCA9E 1:30:49
Response of SDF Systems to Harmonic Loading - Part 2 y2u.be/bh8DTlu3urU 1:24:59
Response of SDF Systems to Harmonic Loading – A Recap y2u.be/Li6Of0tlOjc 48:04
Periodic Loading
Response of SDF Systems to Periodic Loading – Part 1 y2u.be/9ueH32NpRkc 25:25
Response of SDF Systems to Periodic Loading – Part 2 y2u.be/1reOQ18—gQ 53:09
Solved Examples – Harmonic/Periodic Responses of SDF Systems y2u.be/YEg15kIaoF4 17:23
Impulse Loading Response of SDF Systems to Impulse Loading y2u.be/GVov4SyM2Nc 18:42
General Loading
Response of SDF Systems to General Dynamic Loading – Part 1 y2u.be/TWkCBCZiDuM 43:16
Response of SDF Systems to General Dynamic Loading – Part 2 y2u.be/Ow3V4tKQW9c 1:14:34
ETABS Modeling of a Single-Degree-of-Freedom (SDF) System y2u.be/iLlC0h6W6Oo 25:08
Earthquake
Response of SDF
Systems
Concept of Elastic Response Spectrum y2u.be/08FqAqrpbLc 36:51
Elastic Response Spectrum of a Ground Motion – An Introduction y2u.be/ckpzOp5ivrc 29:44
Basic Processing of Ground Motion Records using SeismoSignal y2u.be/cGEJ6yX9VsY 33:28
Dynamics and Earthquake Response of Simple (Elastic) Structures - A Quick Summary y2u.be/tjdMQs3ZmUc 1:20:46
The Concept of Elastic Design Spectrum y2u.be/DVt0R_0063Q 30:25
The Concept of Inelastic Response Spectrum y2u.be/BYjM7N8FOtI 1:39:20
Chapter Topic Videos YouTube Link Duration
Dynamics of
Simple
Structures
Generalized SDF
Systems
Generalized Single Degree of Freedom Systems - Part 1 y2u.be/73kwkfCG0yA 1:17:02
Generalized Single Degree of Freedom Systems - Part 2 y2u.be/pt6AnqqDvaI 1:11:57
Chapter Topic Videos YouTube Link Duration
Dynamics of
Discrete MDF
Structures
MDF Systems Formulation of Mathematical Model for MDF Systems y2u.be/YuD1gdpSbPs 31:09
Free Vibration
Free Vibration Response of MDF Systems y2u.be/XlEsGZ37vG0 1:11:27
Classical Modal Analysis of Building Structures and Interpretation of Results Using CSI
ETABSy2u.be/KZgTFseW3Kc 44:29
Orthogonality Property of Mode Shapes - ETABS Demonstration y2u.be/nrI50lhfv6A 26:49
Forced Vibration
Response of MDF
Systems
Mode Superposition Method for the Dynamic Analysis of Structures y2u.be/z16tSTs91PM 1:03:19
Modal Damping and Rayleigh Damping Models - ETABS Demonstration on Damping in
Dynamic Analysisy2u.be/4rgTdWGbmpQ 34:54
Numerical Evaluation of Dynamic Response of MDF Systems - Step-by-step Direct
Integration Methody2u.be/re_qK_UHStE 1:15:25
Determination of Mode Shapes and Natural Frequencies of MDF Systems using MATLAB y2u.be/MywS__AXBL8 12:38
Assignments - Dynamic Response of MDF Structures y2u.be/SohHK6Ax1AM 16:26
Dynamics of
Continuous
Structures
Continuous
Structures
Formulation of Equations of Motion and Free Vibration Response y2u.be/FdjtVdVHiyg 1:33:23
Modal Orthogonality and Forced Vibrations Response y2u.be/DBJVIB4WEgQ 39:45
SDF Systems – Discrete MDF Systems – Continuous Systems (A Quick Summary) y2u.be/O-eVoopUmRY 12:33
Wave Propagation Introduction to Wave Propagation y2u.be/0c5M1KlK3b8 1:23:12
Random Vibrations
Probability theory, random processes
Correlation and spectral density functions
Response to stationary random excitations
Crossing, peak distributions, extreme value analysis, evaluation of fatigue life
Control of Dynamic ResponseOverview of vibration control
Tuned Mass Dampers
Active vibration control
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Reference Books
• A. K. Chopra, (2017): Dynamics of Structures-Theory and Applications to Earthquake Engineering, ISBN
0134555120, 9780134555126, Prentice Hall international series, Pearson, 2017.
• R. W. Clough, and J. Penzien, (2003): Dynamics of Structures, Computers and Structures, Incorporated, ISBN
0923907505, 9780923907501.
• Roy R. Craig, (2010): Structural dynamics: An introduction to computer methods, ISBN 0471044997, Wiley.
• J. W. Smith, (1988): Vibration of Structures: Applications in Civil Engineering Design, Chapman and Hall,
London.
• T. R. Tauchert, (1974): Energy Principles in Structural Mechanics, McGraw-Hill, ISE.
• H. Bachmann, and W. Ammann, (1987): Vibrations in Structures-Induced by Man and Machines, Series:
Structural Engineering Documents. Vol. 3e. International Association for Bridge and Structural Engineering
(IABSE), Zurich, Switzerland.
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Reference Books
• D. E. Newland, (1993): An Introduction to Random Vibrations, Spectral and Wavelet Analysis,
Longman, 3rd Edition, London.
• S. H. Crandall, and W. D. Mark, (1963): Random Vibration in Mechanical Systems, Academic Press,
New York.
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Journals and Magazines
• Earthquake Engineering and Structural Dynamics, Wiley
• Engineering Structures, Elsevier
• Structural Design of Tall and Special Buildings, Wiley
• Journal of Structural Engineering, ASCE
• Soil Dynamics and Earthquake Engineering, Elsevier
• Journal of the engineering mechanics division, ASCE
• Magazine of Concrete Research, ICE
• Structures and Buildings, ICE
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Evaluation Scheme
• The final grade will be computed according to the following weight distribution:
• One Hour Tests: 30%
• Assignments: 10%
• Quizzes: 10%
• Final Exam: 50%
• Link for downloading course material.
www.structurespro.info
www.fawadnajam.com
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• Monday to Friday – Working Hours
• Office No. 14, Ground Floor, PG Wing Building, SCEE, NUST
Instructor and Contact
Fawad A. NajamDepartment of Structural Engineering
NUST Institute of Civil Engineering (NICE)
National University of Sciences and Technology (NUST)
H-12 Islamabad, Pakistan
Cell: 92-334-5192533, Email: [email protected]
Thank you