cie 619 chapter 1 introduction handout

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DEPARTMENT OF CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING

CIE619 - STRUCTURAL DYNAMICS AND EARTHQUAKE ENGINEERING IISpring 2009

Instructor: Andrei M Reinhorn, PhD, PE

Office: 135 Ketter HallE-mail: [email protected] Website: http://civil eng buffalo edu/cie619

Chapter 1 - Introduction 1

Chapter 1 - Introduction

Course Website: http://civil.eng.buffalo.edu/cie619TA: TBA

*Notes: Andre Filiatrault (modified by Andrei M Reinhorn)

GENERAL OBJECTIVES The CIE 619 course allows structural engineers to consolidate their knowledge on the effect of earthquake ground motions on civil engineering structures. The course willcover the analysis and the design of structures made of various materials that are locatedin active seismic zones. The course will also introduce the use of supplemental dampingand seismic isolation systems to raise the seismic performance of buildings and bridges. The course will also call upon the critical sense of structural engineers in order to allowthe seismic evaluation of existing structures.


Finally, the course will allow structural engineers to acquire new basic knowledge inearthquake engineering that will allow them to communicate better with scientists and engineers of other disciplines in earthquake engineering (e.g. seismologist, geotechnicalengineers, etc.).

1. INTRODUCTION TO EARTHQUAKE ENGINEERING At the end of this chapter, structural engineers will have an appreciation of the history ofthe development of earthquake engineering worldwide and will also gain knowledge onthe development of seismic provisions in US building codes.

2. ELEMENTS OF SEISMOLOGY AND SEISMICITY At the end of this chapter, structural engineers will have acquired basic sufficientknowledge in seismology and seismicity in order to correctly interpret the “language” ofseismologists. They also will be able to perform simple calculations on recorded groundmotions.


3. ELEMENTS OF SEISMIC HAZARD ANALYSIS

At the end of this chapter, structural engineers will understand the basis of the proceduresused to determine the seismic hazard level at a given based on past seismicity of the region, the level of attenuation of seismic waves and the design return period. Thus, theywill be able to appreciate the origin of seismic hazard maps contained in current USbuilding codes.

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SUGGESTED TEXTBOOKS: Elements of Earthquake Engineering and Structural Dynamics, Second Edition, AndréFiliatrault, Polytechnic International Press, 2002. Dynamics of Structures: Theory and Applications to Earthquake Engineering, ThirdEdition, Anil K. Chopra, Prentice Hall. Earthquakes – 4th Edition, Bruce A. Bolt, W.H. Freeman and Company, New York.


Principles of Passive Supplemental Damping and Seismic Isolation, ConstantinChristopoulos; Andre Filiatrault, IUSS Press, 2006.

Additional References will be introduced in specific lectures

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Week Topic Sections in TextbooksFiliatrault Chopra Bolt Christopoulos

1 Element of Seismology and Seismicity 2.1 to 2.14 --- 1 - 7 ---2

3 Seismic Hazard Analysis 3.1 to 3.4 ‐‐‐ ‐‐‐ ‐‐‐

4 Dynamic Analysis of Structures 4.2.3, 4.3 -4.9

18.1 - 18.719.1 - 19.4

--- 2.1 - 2.75678 Principles of Seismic Design 6.1 - 6.5 21.1 - 21.9 12 2.1 - 2.7

Recess

References


9 Principles of Seismic Design 6.7 - 6.12

10 Energy Concepts 9.1 - 9.4 --- --- 3.1 - 3.51112 Introduction to

Passive Supplemental Damping and Seismic Isolation

9.5 - 9.8 20.1 - 20.5 --- 4.1 - 4.45.2, 5.5 -

5.66.2 - 6.4, 6.6,

7.1, 7.6 -7.11, 9.1, 10.2 - 10.5

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14 Projects Oral Presentations ---

Schedule Detailed

GRADING POLICY: Evaluation % of Final Mark

Assignments / Homeworks 30% Project Report 25% Project Oral Presentation 15% Final Examination 30%

Exams Materials: All exams are open materials (any), however, no material can be shared under any circumstances GRADES ASSIGNMENT The final grade will be assigned according to the University policies (i.e. A, A-, B+, B, B-, C+, C, F, using a uniform distribution in steps of five points (A=95 and above F=64 and below)


uniform distribution in steps of five points (A 95 and above, F 64 and below). A A- B+ B B- C+ C F

95-100 90-94 85-89 80-84 75-79 70-75 65-69 0-64 You MUST have a passing average in the individual examination, in order to pass this class. Failure to have a passing average of 50 will automatically result in an F grade. “Incomplete grades” will not be assigned, except for serious and well-documented reasons.

PROJECT DESCRIPTION The objective of the project is to perform the visual screening of an existing building forpotential seismic hazard. Students are divided into teams of three or four during the firstlecture. The visual screening will be based on the FEMA-154 procedure published by the Federal Emergency Management Agency. This procedure does not require the use ofstructural drawings. Each team will need to identify the building of their choice, perform the visual screeningfollowing the FEMA 154 procedure and complement it, if needed, with other analysisprocedures of their choices. Single-story buildings cannot be selected. Buildings on the


p g y g gcampus of the University at Buffalo (UB) can be selected. Architectural and structural drawings for UB buildings can be obtained by contacting Ronald C. Van Splunder at 645 6339 x 338 or [email protected]. Each team will hand in only one project report at the last lecture summarizing their workand providing a final opinion on the potential seismic vulnerability of their building. Thereport must also provide preliminary retrofit procedures, if needed. After the last lecture, each team will make an oral presentation to the class on the mainfindings of their project. This session will be open to the public.

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The project will be evaluated on the following:

The thoroughness of the rapid visual screening procedure and the resourcefulnessdemonstrated by the team.

The technical level of the complementary analysis procedures (if any). The quality of the presentation. The adequacy of the retrofit procedure proposed (if any). The quality of the oral presentation.



IMPORTANT DATES February 5, 2008: Selection of the building: each team must hand-in a one page

containing a brief summary of the building that they have selected including: buildingname, building location, No. of stories, Structural type, a photo of the building.

March 4, 2008: Progress Report: each team must a hand-in a one-page progress

report on their project.

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April 24, 2008: Project report: each team must hand-in their final project report.

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PROJECT REPORT FORMAT*

The Project report must be limited to 10 pages (extra pages will not be read) and mustinclude the following items: 1. Title page

a) Title: RAPID VISUAL SCREENING OF THE (name of building) BUILDINGS FOR POTENTIAL SEISMIC HAZARDS – CIE 619 SPRING 2008

b) Team name (find one!) c) Group symbol/logo (make one up!) d) Names of team members e) Signatures team members (very important) f) Date

2. Summary (one page) 3. Description of Building


Building location, address, No. of stories, Year built (approx), Total floor area (approx), Type of occupancy, Structural type, Soil type, etc.

4. FEMA-154 Visual Screening Procedure

a) Description of Procedure b) Results Obtained

5. Complementary Analysis Procedures (if any)

a) Description of Procedures Used b) Results Obtained

6. Final Seismic Risk Evaluation 7. Proposed Retrofit Procedure (if any). *Items 1 to 4 are minimum grade requirements for the project report

Importance of Earthquake Engineering




(Coburn and Spence, 2002)

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(1,685,000 total fatalities in 20th century)







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Earthquake Energy

Sumatra-Andaman (2004)

Chapter 1 - Introduction

Source: EERI Slides & Earthquakes by Bruce A. Bolt

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BRIEF HISTORY OF EARTHQUAKE ENGINEERING

• Young science

• Seen its major developments in 20th century

• At Eighth World Conference on Earthquake


• At Eighth World Conference on Earthquake Engineering held in San Francisco in 1984, George Housner presented historical review of major developments in earthquake engineering


• Foundations of earthquake engineering elaborated in 18th and 19th centuries by British scientists (although England is a country of low seismicity)

• Industrial revolution (1700 to 1900) strongly


• Industrial revolution (1700 to 1900) strongly influenced developments in various sciences

• Robert Hooke (1635-1703), known for his famous elasticity law, was one of first scientists involved with earthquake phenomenon – Between 1667 and 1668, gave several talks on earthquakes

and volcanoes at Royal Society of London


• In 19th century: no distinction between seismology and earthquake engineering

• Seismology derived from Greek word «sismo» or «vibration»– used for the first time by British engineer Robert Mallet (1810-1881)


y g ( )– also introduced now well known terms «epicentre» and «focal point».

• In 1848, Mallet published concepts for elaboration of first electromagnetic seismograph– instrument was never built

• Italian born Luigi Palmieri (1867-1896) modified Mallet’s idea to build first automatic seismograph and obtain the first modern earthquake records

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• John Milne, James Ewing and Thomas Gray, teaching at the Imperial College of Engineering in Tokyo, founded Seismological Society of


y , g yJapan – In 1880, became first scientific association entirely

dedicated to the study of seismic phenomena

– Forerunner of International Association for Earthquake Engineering


• At turn of the century, three major earthquakes strongly contributed to further development of knowledge related to seismic phenomena


– 1891: Mino-Awari (Japan)

– 1906: San Francisco (USA)

– 1908: Messina (Italy). • happened on December 28th 1908

• more than 83 000 people died

• led to first construction methods to sustain earthquakes and, therefore, the science of earthquake engineering.


• Italian government set up special committee made up of nine practicing engineers and five engineering professors– mandate to study 1908 Messina earthquake and formulate

recommendations. – in committee’s report, M. Panetti professor of applied mechanics at the


p , p ppUniversity of Turin, proposed that for active seismic zones, civil engineering structures be calculated with a uniform static lateral load represented by «seismic coefficient » expressed as fraction of structure’s weight

– also emphasized that effects of earthquakes on structures are in fact a «structural dynamics» problem

– yet this problem «much too complicated» to address, and equivalent static approach was preferred for design of earthquake resistant structures

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• Static approach remained in use until engineers finally gained access to powerful computers

• In 1909, A. Danusso, professor of structural engineering at University of Milan, published a paper that explained in detail application of the static approach proposed by Panetti St ti th d l l i t t d i b ildi d d t i d f


• Static method was slowly integrated in building codes and sustained few modifications until the 1940's

• After Tokyo’s great earthquake of 1923, Japanese seismic provisions adopted a seismic coefficient of 10%.

• City of Los Angeles adopted a seismic coefficient of 8% following 1933 Long Beach earthquake

• Seismic coefficient that varies with height of structure was introduced only in 1943

– birth of the static approach method as found in modern building codes.



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COMPUTERS AND EARTHQUAKE ENGINEERING

• Evolution of computers, from analog to digital, paramount for earthquake engineering

• Computers allowed earthquake records to be analyzed in a reasonable amount of time

• Cornerstone in the application of «seismic response spectrum» method, proposed by George Housner (1910 -2008 ) at the beginning of the 1950's


g ( ) g g• Computers also allowed dynamic analysis of structures subjected to seismic

excitations – this type of analysis, qualified by Panetti as «much too difficult» in 1908, was now

readily accessible to engineers • Numerical procedures, such as finite element method, were also used in dynamic

analyses of complex structures • Although powerful computers were beneficial to earthquake engineering, machines

can not replace the judgment of structural engineers • Design and building of an earthquake resistant structure is as much a science as it is

an art

COMPUTERS AND EARTHQUAKE ENGINEERING

• Past 10 years has seen rapid innovation in the practice of earthquake engineering.

• Computational tools, including:


– OpenSees (http://opensees.berkeley.edu/)

– IDARC (http://civil.eng.buffalo.edu/idarc2d50/)

– SAP 2000 NL (http://www.csiberkeley.com/)

– 3-D BASIS (http://civil.eng.buffalo.edu/3dbasis/)

– RUAUMOKO (http://www.civil.canterbury.ac.nz/ruaumoko/index.html)

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EXPERIMENTAL EARTHQUAKE ENGINEERING

• Although powerful computers allow dynamic analysis of complex structures, earthquake engineering is not beyond experimental testing


g g y p gmethods

• Laboratory experimentation remains necessary tool to maintain adequate level of seismic protection for civil engineering structures


• Around the world, experimental research is used to study behavior of elements, of assemblies and of complete structural systems in a seismic environment


• In experimental earthquake engineering research , three types of tests may be performed: – a) quasi-static test

– b) pseudo-dynamic/hybrid test

– c) shake table test


• Quasi-static test:– inertia forces generated by an earthquake on a structure replaced by

equivalent static loads – hydraulic actuators produce static forces between a reaction frame and

a specimen


– generally performed on large scale structural elements – basic information, such as strength, stiffness and ductility, obtained to

predict the behavior of a structure – results used to validate and develop numerical models – may be interrupted at any time to assess the condition of the specimen – main weakness: comparison between the specimen’s ability to dissipate

energy and the energy dissipation capacity required to ensure seismic safety; constant problem is to know whether specimen is overloaded or not

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• Quasi-static test



• Pseudo-dynamic/hybrid test – combine quasi-static tests with a numerical analysis to simulate seismic

response of a structure– speed much slower than speed of a real earthquake– directly measure internal forces at specific points on structure within a given

ti i t l


time interval – Forces used to solve numerically system’s equations of motion and calculate

resulting displacements– hydraulic actuators provide calculated displacements on specimen. – limitations :

• materials sensitive to strain-rate effects may produce results that are invalid in a real earthquake.

• because of low speed, can not test viscoelastic damping systems• because of cost , only few hydraulic actuators are used, thereby limiting the number

of degrees-of-freedom


• Shake table test – only experimental technique allowing to directly simulate inertia forces

on a structure with distributed mass – can reproduce different types of ground motions such as recorded

earthquakes synthetic accelerograms or simple signals such as sine


earthquakes, synthetic accelerograms or simple signals such as sine waves

– ground motion intensity can be increased to induce inelastic response of specimen.

– allow evaluation of nonlinear response and failure modes of structures in realistic seismic environment.

– major weakness: load bearing capacity of the testing platform • in most cases, small scale testing is used

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• Shake table test








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The 1995 Kobe Earthquake

’06 The next Great Quake


Questions/Discussions


cie 619 chapter 1 introduction handout

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