study on response reduction factor of rc watertank

7/21/2019 STUDY ON RESPONSE REDUCTION FACTOR OF RC WATERTANK

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A STUDY ON RESPONSE REDUCTION FACTOR OF RC WATER TANK

By

MILAN H MANEK

(Enrolment No. 130540720006)

Guided By

Prof. D.K.JIVANI (M.E. CASAD)

Prof. Civil Engg. Dept., DIET, Hadala

A Thesis Submitted to

Gujarat Technological University

In partial Fulfilment of the Requirements for

The Degree of Master of Engineering

In Civil-Structural Engineering

JANUARY-2015

DARSHAN INSTITUTE OF ENGINEERING & TECHNOLOGY, RAJKOT-MORBIHIGHWAY, HADALA.


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CERTIFICATE

A STUDY ON

RESPONSE REDUCTION FACTOR OF RC WATER TANK Mr.

MILAN H MANEK 130540720006

Seal of Institute

This is to certify that the work embodied in this dissertation entitledwas carried out by

(Enrolment No. ) at D.I.E.T., Hadala for partial fu lfilmentto M.E. Civil Engg.(Structural) degree to be awarded by Gujarat Technological University.This research work has been carried out under my supervision and is to my satisfaction.

Date:Place: Hadala

Prof. D.K.Jivani Dr. R. G. Dhamsania

(Guide) Principal

D.I.E.T, Hadala D.I.E.T, Hadala


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DECLARATION OF ORIGINALITY

Signature of Student:

Name of Student: MILAN H MANEK

Enrollment No: 130540720006 Signature of Guide:

Name of Guide: PROF. Dipak K. Jivani

Institute code: 054

I hereby certify that I am the sole author of this thesis and that neither any part of this thesis northe whole of the thesis has been submitted for a degree to any other University or Institution.

I certify that, to the best of my knowledge, my thesis does not infringe upon anyonescopyright nor violate any proprietary rights and that any ideas, techniques, quotations, or any

other material from the work of other people included in my thesis, published or otherwise, are

fully acknowledged in accordance with the standard referencing practices. Furthermore, to the

extent that I have included copyrighted material that surpasses the bounds of fair dealing

within the meaning of the Indian Copyright Act, I certify that I have obtained a writtenpermission from the copyright owner(s) to include such material(s) in my thesis and haveincluded copies of such copyright clearances to my appendix.

I declare that this is a true copy of my thesis, including any final revisions, as approved by mythesis review committee.

Date:

Place: RAJKOT


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THESIS APPROVAL

This is to certify that research work embodied in this entitled A

STUDY ON RESPONSE REDUCTION FACTOR OF RC WATER TANK

Mr. MILAN H MANEK (Enroll No.130540720006) at Darshan institute

of Engineering and Technology, Rajkot

Date:

Place:

Examiner(s):

( ) ( ) ( )

----------------------- ---------------------- --------------------------

was

carried out by

is approved for award of the degree of M.E.

Civil (St ructure) by Gujarat Technological University.


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ACKNOWLEDGMENTS

MILAN H MANEK

Enroll No.130540720006

I would like to extend my heartiest thanks with a deep sense of gratitude and respect to all

those who provided me immense help and guidance during the research.

I would like to thank my dissertation guide Prof. D. K. JIVANI Professor,

Structural Engineering department, DIET, Rajkot for providing a vision about the

dissertation. I have been greatly benefited from the regular critical reviews and

inspiration throughout my work.

I would also like to thank my Professors for their unfailing cooperation and

sparing their valuable time to assist me in my work. I have developed not only technical skills

but also learned a ll those qualities required to become a good professional engineer.

Last but not least, I would like to mention here that I am greatly indebted to each and

everybody who has been associated with this research at any stage but whose name does not

find a place in this acknowledgment.


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ABSTRACT

The main purpose of earthquake resisting design is is that the structure should not

permitted to collapse but damage is allowed during earthquake. water tank is importantstructure. Staging type of tanks are generally collapse during earthquake , so it is required

to calculate earthquake load perfectly. Past evidence had shown that the elevated tanks are

vulnerable due to earthquake. The tanks are designed based on linear elastic methods

which are considered only elastic range. factor shows the reserved strength of water tank.in

IS 1893-2002(part-2)value of R factor for RC elevated shaft supportd tank is 1.8 and for

column supported 2.5. One constant R-value for elevated water tank cannot reflect the

expected inelastic behavior of all elevated water tanks located in different seismic

zone and having different staging pattern.So it is required to find out perfect value of R

factor for various type of RC elevated tank individually. The present study efforts are

made to evaluate the response reduction factor of RC framed staging elevated water tank

having varying staging height, capacities, staging type and zones. The main objective

of this study is to verify the R factor of most common designed Elevated Intze tank through

comparing the assumed R factor during design to actual R factor obtained from non-linear

analysis.


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TABLE OF CONTENTS

Title Page No.

ACKNOWLEDGEMENTS.............................................................................................. 5

ABSTRACT...................................................................................................................... 6

TABLE OF CONTENTS...................................................................................................7


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INDEX

CHAPTER 1 INTRODUCTION.9

CHAPTER 2 LITERATURE REVIEW12

1.1 Overview91.2 Need For the Present Study..10

1.3 Objective ..11

1.4 Scope of work...................................11

2.1paper1.12

2.2paper 2....15

2.3paper 3....17

2.4 paper 4.................................................. ................................................... ...........................18

2.5paper 520

2.6 paper 6....21

2.7 paper 7....22

2.8 paper 8................................ ........................................................ ........................................23


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CHAPTER-1 INTRODUCTION

1.1 Over View:

Water Is Considered As The Source Of Every Creation And Is Thus A Very Crucial Element For

Humans To Live A Healthy Life. High Demand Of Clean And Safe Drinking Water Is Rising

Day By Day As One Can Not Live Without Water. It Becomes Necessary To Store Water. Water

Is Stored Generally In Concrete Water Tanks And Later On It Is Pumped To Different Areas To

Serve The Community.

One Of The Oldest Known Water Tanks In Kenya Was Built By The Railway At Makindu River

In 1907. It Appears The Tank Was Connected To A Hydram Pump That Used The Power Of The

Flowing Water In The River To Push Water Into The Tank From Where It Was Used By Steam

Locomotives.

Water Tanks Can Be Classified As Overhead, Resting On Ground Or Underground Depending

On Their Location. The Tanks Can Be Made Of Steel Or Concrete. Tanks Resting On Ground

Are Normally Circular Or Rectangular In Shape And Are Used Where Large Quantities Of

Water Need To Be Stored.

Overhead Water Tanks Are Used To Distribute Water Directly Through Gravity Flow And Are

Normally Of Smaller Capacity. As The Overhead Water Tanks Are Open To Public View, TheirShape Is Influenced By The Aesthetic View In The Surroundings.


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1.2 Need Of Study:

R As Per International Standards For Elevated Tanks:

Generally Staging Type Over Head Tanks Collapse In Earthquake . It Is Very Important To

Consider Earthquake Load In Design Of Elevated Tank.

Response Reduction Factor (R) Is Very Important To Find Out Earthquake Load.The Response

Reduction Factor Reflects The Capacity Of Structure To Dissipate Energy By Inelastic Behavior.

The Values Of Response Reduction Factor(R) Of Rc Elevated Water Tank Are Given In Is

1893 Draft Code, Which Is Arrived At Empirically Based On Engineering Judgment. The

Values Of Response Reduction Factor Of Elevated Water Tank Adopted By Difference

Codes/Standards Are Summaries Below.

odes/Standards R Factor

bc 2000/ Fema 368 .5 To 3.0

ci 350.3 .0 To 4.75

s:1893-2002(Part -2) Rcc Frame Support

Draft Code)

.8 (Omrf)

Smrf)

The Value Of R-Factor Is Fixed 2.5 For Frame Supported Rc Elevated Tank.One Constant

R-Value For Elevated Water Tank Cannot Reflect The Expected Inelastic Behavior Of All

Elevated Water Tanks Located In Different Seism ic Zone And Having Different

Capacities.So It Is Required To Find Out Perfect Value Of R Factor For Various Type Of Rc

Elevated Tank Individually.


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1.3 Objectives:

1.5Scope Of Work:

The Main Objective Of This Study Is To Verify The R Factor Of Most Common

Designed Elevated Intze Tank Through Comparing The Assumed R Factor During

Design To Actual R Factor Obtained From Non-Linear Analysis. The Specific

Objectives Of The Study Are To:

Conduct Static Non-Linear (Pushover) Analysis And Calculate R Factor Of E levated

Intze Tank

Prepare A Spreadsheet To Design Elevated Tank

Compare The Calculated R Factor With The Assumed R Factor.

Evaluate Ductility, Redundancy And Over Strength Factor Of Elevated Intze Tank

Study The Effect Of Staging Height And Staging Type On Response Reduction Factor

(R).

To Study Effect Of Zone Factor On Response Reduction Factor (R).

To Prepare A Spreadsheet And Design Water Tank As Per Is- 3370:2009 (Limit State

Method).

Understand The Procedure Of Water Tank Modelling And Pushover Analyses In SapSoftware Considering Hydrodynamic Pressure As Per Iitk-Gsdma Guidelines.

To Perform Pushover Analysis Of Elevated Water Tank For Different Capacity, Height ,

Zone And Compare The Results.

Perform A Comparative Study Between Different Staging Patterns In Form Of Variation In

Ductility, Redundancy And Over Strength Factor Etc

Calculated And Compare The Calculated R Factor With The Assumed R Factor


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Chapter-2 Litrature Review

2.1 Evaluation Response Reduction Factor Of Rc Framed Staging ElevatedWater Tank Using Static Pushover Analysis( Tejash Patel1, Jignesh Amin2,

Bhavin Patel3 1- Post Graduate Student, Svit, Vasad, October, 2013

Published On February 2014

215)

Severe Damages Were Observed In Buildings, Public Utility Structures Like Water Tanks And

Hospitals During 26th January 2001 Bhuj Earthquake. Earthquake Can Induce Large Horizontal

And Overturning Forces In Elevated Water Tanks And Are Quite Vulnerable To Damage InEarthquakes Due To Their Basic Configuration Involving Large Mass Concentrated At Top

With Relatively Slender Supporting System. The Basic Principal Of Designing Structures For

Strong Ground Motion Is That The Structure Should Not Collapse But Damage To The

Structural Elements Is Permitted. Since A Structure Is Allowed To Be Damaged In Case Of

Severe Shaking, The Structure Should Be Designed For Seismic Forces Much Less Than What

Is Expected Under Strong Shaking, If The Structures Were To Remain Linearly Elastic.

Response Reduction Factor Is The Factor By Which The Actual Base Shear Force Should Be

Reduced, To Obtain The Design Lateral Force. Base Shear Force Is The Force That Would Be

Generated If The Structure Were To Remain Elastic During Its Response To The Design Basic

Earthquake (Dbe) Shaking. Ozhendekci Et Al. (2006) Evaluated The Seismic Response

Modification Factor For Eccentrically Braced Frames. Conclusion Was Made That One

Constant R-Value Cannot Reflect The Expected Inelastic Behavior Of All Building Which Have

The Same Lateral Load Resisting System. Pore Et Al. (2006) Described Effect Of Response

Reduction Factor In Performance Based Seismic Design Of Rc Building For India.

The Values Of Response Reduction Factor Of Rc Elevated Water Tank Are Given In Is 1893

(Part-Ii) 2002, Which Is Arrived At Empirically Based On Engineering Judgment. The Values

Of Response Reduction Factor Of Elevated Water Tank Adopted By Difference

Codes/Standards Are Summaries In Table.


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odes/Standards R Factor

bc 2000/ Fema 368 .5 To 3.0

ci 350.3 .0 To 4.75

s:1893-2002(Part -2) Rcc Frame Support

Draft Code)

.8 (Omrf)

.5 (Smrf)

One Constant R-Value For Elevated Water Tank Cannot Reflect The Expected Inelastic

Behavior Of All Elevated Water Tanks Located In Different Seismic Zone And Having

Different Capacities. In The Present Study Efforts Are Made To Evaluate The Response

Reduction Factor Of Five Existing Rc Framed Staging Elevated Water Tanks Having Staging

Height Of 12 M But Having Varying Capacities. The Effects Of Seismic Zone And Fundamental

Time Period Of Water Tank On The Response Reduction Factor Are Also Discussed

The Concept Of R Factor Is Based On The Observations That Well Detailed Seismic Framing

Systems Can Sustain Large Inelastic Deformations Without Collapse And Have Excess Of

Lateral Strength Over Design Strength. Response Reduction (R) Factors Are Essential SeismicDesign Tools, Which Are Typically Used To Describe The Level Of Inelasticity Expected In

Lateral Structural Systems During An Earthquake. The Response Reduction Factor (R) Is

Depends On Over Strength (Rs), Duct ility (R), Redundancy (Rr).

Over Strength Factor (Rs) Accounts For The Yielding Of A Structure At Load Higher Than The

Design Load Due To Various Partial Safety Factors, Strain Hardening, Oversized Members,

Confinement Of Concrete. Non-Structural Elements Also Contribute To The Over Strength.

Ductility Factor (R) Is A Ratio Of Ultimate Displacement Or Code Specified Permissible

Displacement To The Yield Displacement. Higher Ductility Implies That The Structure Can

Withstand Stronger Shaking Without Collapse. Redundancy Factor (Rr) Depends On The

Number Of Vertical Framing Part icipate In Seismic Res istance. Yielding At One Location In

The Structure Does Not Imply Yielding Of The Structure As A Whole. Hence The Load

Distribution, Due To Redundancy Of The Structure, Provides Additional Safety Margin.

Concept Of Response Reduction Factor:


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In Present Study Five Rc Elevated Water Tanks Having A Capacity Of 20m3, 30m3, 50m3,

60m3, And 70m3 Are Considered. For All The Tanks, The Height Of Staging Is 12m And

Staging Comprise Of 4 Columns.

Etabs V.9.5 Software Is Used To Perform The Non Linear Static Pushover Analysis. The Rc

Beams And Columns Are Modeled As 3-D Frame Elements With Centerline D imension. Slabs

Are Modeled As Membrane Elements And Are Assumed To Behave As Rigid Diaphragms.

Column Foundations Are Assumed To Be Fixed. Damping Ratio Of 5 Percent Is Assumed For

All Natural Modes. Flexure Moment (M3), Axial Biaxial Moment (P-M2-M3) And Axial

Compressive Shear Force (V) Hinges Are Assigned At The Face Of Beam, Column, And

Bracing Respectively Using The Static Pushover Analysis.

In Order To Achieve The Objective, The Following Procedure Was Adopted 1. Developing A

Three Dimensional Model Of Existing Rc Frame. 2. Application Of Gravity Loads, Live Loads,Water Load, Etc. 3. Application Of Static Lateral Load Induced Due To Earthquake, At Cg Of

Container 4. Developing M-T & V- ? Relationship For Rc Trestle. 5. Pushing The Structure

Using The Load Patterns Of Static Lateral Loads, To Displacements Larger Than Those

Associated With Target Displacement Using Static Pushover Analysis 6. Developing Pushover

Curve And Estimating The Force And Deformations In Each Element At The Level Of

Displacement Corresponding To Target Displacement 7. In This Study The Response Reduction

Factor (R) Of Exiting Rc Framed Elevated Water Tank Having A 12m Height Of Staging But

Different Capacities Are Evaluated. The Significant Outcomes Of Works Are Summarized As

Follows: 1. The Response Reduction Factor Is Considerably Affected By The Seismic Zone And

Fundamental Time Period Of Water Tanks. It Reduces As The Seismic Zone Increases And

Increases As The Fundamental Time Period Increases. 2. To Ensure The Consistent Level Of

Damaged, Values Of Response Reduction Factor Should Be Based On Both Fundamental Period

Of The Staging And Type Of Soil. 3. The Values Of Response Reduction Factor For A Given Rc

Framing System Should Vary Between Seismic Zones. Also The Reinforcement Detailing

Requirements Should Vary With Seismic Zone. 4. Estimation Of Response Reduction Factor

With Exact Analysis Will Help In An Economical Design. 5. It Is Observed That Response

Reduction Varies From 2.63 To 4 For Tank In Full Condition In Seismic Zone V.


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2.2 Formulation Of Response Reduction Factor For Rcc Framed Staging Of

Elevated Water Tank Using Static Pushover Analysis

(Mr. Bhavin Patel And Mrs. Dhara Shah)Earthquake Can Induce Large Horizontal And Overturning Forces In Elevated Water Tanks.

Such Tanks Are Quite Vulnerable To Damage In Earthquakes Due To Their Basic Configuration

Involving Large Mass Concentrated At Top With Relatively Slender Supporting System. When

The Tank Is In Full Condition, Earthquake Forces Almost Govern The Design Of These

Structures In Zones Of High Seismic Activity. It Is Important To Ensure That The Essential

Requirement Such As Water Supply Is Not Damaged During Earthquakes. In Extreme Cases,

Total Collapse Of Tanks Shall Be Avoided. However, Some Repairable Damage May Be

Acceptable During Shaking Not Affecting The Functionality Of The Tanks

Evere Damages Were Observed In Buildings, Public Utility Structures Like Water Tanks And

Hospitals During 26th January 2001 Bhuj Earthquake. Is:18931984 Does Not Count The

Convective Hydrodynamic Pressures In The Analysis Of Tank Wall And Assumes The Tank As

A Single Degree Of Freedom Idealization. The Accurate Approach For Analysis Of Water Tank

Is To Model The Tank With Two Masses Representing The Impulsive As Well As Convective

Components Of Liquid. Lots Of Research Has Been Made In Two Mass Model Of Esr And

Hydrodynamic Analysis Of The Container. It Has Also Been Observed That A Well Designed

And Well Constructed Water Tank Can Withstand More Lateral Loads Than It Is Designed For

Due To Three Reasons: Over Strength (Rs) Redundancy (Rr) Ductility (R) The Response

Reduction Factor Or Force Modification Factor R Reflects The Capacity Of Structure To

Dissipate Energy Through Inelastic Behavior. It Is A Combined Effect Of Over Strength,

Ductility And Redundancy Represented As

R = Rs * Rr * R.


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Conclusion

There Is No Mathematical Basis For The Response Reduction Factor Tabulated In Indian Design

Codes.

A Single Value Of R For All Buildings Of A Given Framing Type, Irrespective Of Plan And

Vertical Geometry, Cannot Be Justified. But For Esr Staging (BeamColumn Frame Or Shaft),

Where The Basic System Of Framing And Behavior Is More Or Less Common, The Method Can

Be Derived To Evaluate RFactor. Similar Effort Has Been Made Here.

To Ensure The Consistent Level Of Damage, Values Of R Should Depend On Both Fundamental

Period Of The Staging And The Soil Type.

The Values Assigned To R For A Given Framing System Should Vary Between Seismic Zones.

Also Detailing Requirements Vary By Zone.


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2.3 Review Of Code Provisions On Design Seismic Forces For Liquid Storage

Tanks

It Is Well Recognized That Liquid Storage Tanks Possess Low Ductility And Energy Absorbing

Capacity As Compared To The Conventional Buildings. Accordingly, Various Design CodesProvide Higher Level Of Design Seismic Forces For Tanks. In This Article, Provisions Of Ibc

2000, Aci, Awwa, Api, Eurocode 8 And Nzsee Guidelines Are Reviewed, To Assess The

Severity Of Design Seismic Forces For Tanks Vis--Vis Those For Buildings. It Is Seen That,

Depending On The Type Of Tank, Design Seismic Force For Tanks Can Be 3 To 7 Times Higher

Than That For Buildings. Based On The Comparison Of Provisions In These Documents,

Various Similarities, Discrepancies And Limitations In Their Provisions Are Brought Out.

This Article Presents An Assessment Of Design Seismic Force For Tanks Vis- -Vis Design

Seismic Force For Buildings As Mentioned In The Following Documents:

(A) Ibc 2000

(B) Aci Standards Aci 371 (1998) And Aci 350.3 (2001)

(C) Awwa D-100 (1996), Awwa D-103 (1997), Awwa D-110 (1995) And Awwa D-115 (1995)

(D) Api 650 (1998)

(E) Eurocode 8 (1998)


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2.4 Criteria For Design Of Rcc Staging For Overhead Water Tanks

Liquid Tanks Are Important Public Utility And Industrial Structures. Specifications, The Design

And Construction Method In Reinforced Concrete Are Influenced By The Prevailing

Construction Practices, The Physical Properties Of The Material And The Environmental

Conditions.

While The Common Methods Of Design Have Been Covered In This Standard Code, Design Of

Structures Of Special Forms Or In Unusual Circumstances Should Be Left To The Judgment Of

The Design Engineer And In Such Cases Special Systems Of Design & Construction May Be

Permitted On Production Of Satisfactory Evidence Regarding Their Adequacy And Safety By

Analysis Or Test Or By Both

This Draft Standard Lays Down Criteria For Analysis, Design And Construction Of Reinforced

Cement Concrete Staging Of Framed Type With Columns Or Shaft Type, For Achieving A

Desirable Level Safety And Durability Of The Supported Liquid Storage Structure (Container).

Container May Consist Of Any Material Like Rcc, Fiber Concrete, Ferrocement, Steel, Pvc,

Etc.While The Provisions Of This Standard Refer To Stagings For The Storage Of Liquids, The

Recommendations Are Applicable Mainly To Water Storage Or Containment.


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2.5 An Investigation of Seismic Response Reduction Factor for Earthquake

Resistant Design(International Journal of Latest Trends in Engineering and

Technology (IJLTET))

Conclusion:

The present study estimates the seismic Response reduction factor (R) of reinforced concretespecial moment resisting frame (SMRF) with and without shear wall using static nonlinear

(pushover) analysis. Calculation of Response reduction factor(R) is done as per the new

formulation of Response reduction factor (R) given by Applied Technology Council (ATC)-19

which is the product of Strength factor (Rs), Ductility factor (R) and Redundancy factor (RR).

The analysis revealed that these three factors affects the actual value of response reduction factor

(R) and therefore they must be taken into consideration while determining the appropriate

response reduction factor to be used during the seismic design process. The actual values

required for determination of Response reduction factor (R) is worked out on the basis of

pushover curve which is a plot of base shear verses roof displacement. Finally the calcu lated

values of Response reduction factor(R) of reinforced concrete special moment resisting frame

(SMRF) with and without shear wall are compared with the codal values.

Based on above results and observations the following conclusions are drawn.

International Journal of Latest Trends in Engineering and Technology (IJLTET)

1) The Response reduction factor without shear wall is almost reduced by 50% considering

displacement ductility ratio as compared to IS Code values.

2) The Response reduction factor with shear wall are almost doubled considering rotational

ductility ratio as compared to IS code values.

3) The Response reduction factor without shear wall considering rotational ductility ratio was

found to approximately same as compared to IS code values.

4) In case of buildings with shear wall considering rotational ductility ratio there is significant

difference between Response reduction factors and IS code values.5) The Response reduction factor with shear wall considering displacement ductility ratio was

found to approximately same as compared to IS code values.

6) In case of buildings without shear wall considering displacement ductility ratio there is

significant difference between Response reduction factors and IS code values.


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2.6 Seismic Behavior Of Shell-Base Connections In Large Storage

Tanks(Alain Nussbaumer, Martin Kolle 1steel Structures Laboratory

(Icom), Swiss Federal Institute Of Technology, Lausanne, Switzerland)

Conclusions:

Unanchored Steel Tanks Subjected To Strong Ground Motion May Experience Rocking MotionIf The Moment Generated By The Inertial Mass Of The Content Stored Is Greater Than The

Resisting Moment Provided By The Weight Of The Tank And Its Content. Rocking Of The

Tank Causes The Shell-Base Welded Connection To Undergo Cycles Of Rotation. The

Eurocode Provides A Methodology For Estimating The Maximum Rotation That This

Connection May Experience. This Methodology Was Applied To Study Six Tanks Located In

Switzerland And It Was Found That Four Of These Tanks Did Not Satisfy The Rotation Limit

Set By The Code. These Findings Motivated A More Comprehensive Study In Which Two

Tanks Were Analyzed According The Eurocode And New Zealands Recommendations, And

By Means Of A Pushover And A Time History Analysis.

This Paper Investigated The Rotation Demand Provided By The Eurocode, The New Zealands

Recommendations, A Pushover Analysis And A Time History Analysis. Eurocode Results Were

Too Conservative For The Slender Tank (I.E., Rmlang), But Relatively Acceptable For The

Squat Tank Studied (I.E., Mellingen). On The Other Side, The New Zealands

Recommendations And The Pushover Analysis Provided Values Between The Average And

The Maximum Rotation Measured From The Time History Analysis. While More Work Is

Needed To Have Final Conclusions Regarding The Demand Of The Tank, This Investigation

Clearly Points Out That The Eurocode Does Not Provide The Right Means To Estimate The

Rotation Of The Shell-Base Connection In An Above Ground Unanchored Tank.The Time

History Analysis, Explained In Section 3, Provides The Most Information Of The Shell-Base

Connection Behavior. It Provides The Response History Of Deformation And Rotation At The

Connection, From Which The Number Of Cycles And The Amplitude Of Each Cycle AreObtained. The Time History Analysis Is However A Very Time Consuming Procedure,

Requiring That Ground Motions Representative Of The Site Hazard Be Obtained. The

Procedure Is Also Very Expensive Computationally. On The Other Hand, The Pushover

Analysis Can Provide A Good Overall Understanding Of The Behavior Of The Tank While

Being Significantly Less Expensive Than The Time History Analysis.


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2.7 A Case Study Considering A 3-D Pushover Analysis Procedure

( W. Huang And P. L. Gould The 14 Th World Conference On Earthquake

Engineering , October 12-17, 2008, Beijing, China )

Objectives:

Conclusions:

With An Unusually Large Rectangular Duct Opening Located About 1/3 Of The Height Above

The Base, A 115 Meter High Reinforced Concrete Chimney Collapsed During The Earthquake

While Several Other Similar Structures Survived With Only Moderate Damage. Debris Of The

Failed Stack Cut Many Lines, Which Fueled Fires That Shut Down The Refinery For Months.

This Case Study Provides Intriguing Results, Considering That The Stack Was Designed And

Constructed According To International Standards And Is Representative Of Similar Structures

At Refineries Throughout The World. The Main Focus Of The Investigation Is The Dynamic

Response Of The Stack Due To An Earthquake Motion Recorded At A Nearby Site, Named The

Ypt Record. A New 3-D Pushover Analysis Procedure Is Proposed In This Paper And The

Results Will Be Compared With Those Of A Nonlinear Dynamic Analysis. Higher Mode Effects

Are Significant For This Type Of Structure And Considered In The Proposed 3-D Pushover

Analysis Procedure.

To Evaluate The Original Design Of The Collapsed Chimney, Known As The Tpras Stack,

Using Current Analysis Techniques.

To Evaluate The Design Of A Similar Size Chimney Representative Of U. S. Practice

To Explain Why The Single Stack In Question Did Indeed Collapse While Several Similar

Structures In The Same Vicinity Survived With Minimal Damage Through The Use Of

Advanced Seismic Evaluation Tools.

To Extend The Pushover Analysis Procedure For Chimney Structures By Taking Into Account

The Higher Modes And The Three Dimensional Interaction Effects.

A New 3-D Pushover Analysis Procedure Was Proposed And Applied To Models Of Chimneys

With And Without An Opening. Various Lateral Load Patterns Were Considered. For The

Target Displacement Of The Model Without The Opening, The Error From The Uniform

Distribution Was The Largest, While The Mode 1 Distribution, Elf Distribution, And Triangle

Distribution Provided Somewhat Better Estimates. The Srss Distribution Gave A Good


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Prediction, With An Error Around 10% And The Error From The Mpa Procedure Was Even Less

Than 10%. As To The Peak Deflections, The Mpa Procedure And Srss Distribution Provided

The Best Estimates, While The Uniform Distribution Underestimated The Total Response By

Up To 30%. The Mode 1 Distribution, Elf Distribution, And Triangle Distribution Gave Similar

Estimates. Compared To A 2-D Pushover Analysis, The New 3-D Pushover Analysis Procedure

Provides A Better Estimation For Target Displacements.

For The 3-D Pushover Analysis On The Model With The Opening, The Failure Displacements

Predicted Using Different Lateral Patterns Were In An Acceptable Range. The Srss Distribution

Resulted In The Lowest Error, Between 10% And 20%. All Of The Lateral Load Patterns

Successfully Captured The Shear Cracks Developed Around The Opening, Along With Flexural

Cracks.

From The Failure Cracking Pattern For The 3-D Nonlinear Dynamic Analysis, There Were MoreLong Critical Shear Cracks Around The Opening Area Than There Were The Flexural Cracks

Along The Height. This Confirmed The Initial Prediction By 2-D Pushover Analysis That The

Critical Shear Cracking Around The Opening Area, Along With The Concentrated Flexural

Cracking, Was Prominent In The Failure.


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2.8 Pushover Analysis Of A 19 Story Concrete Shear Wall Building

(Rahul Rana, Limin Jin And Atila Zekioglu)

Conclusion:

Pushover Analysis Was Performed On A Nineteen Story, Slender Concrete Tower Building

Located In San Francisco With A Gross Area Of 430,000 Square Feet. Lateral System Of TheBuilding Consists Of Concrete Shear Walls. The Building Is Newly Designed Conforming To

1997 Uniform Building Code, And Pushover Analysis Was Performed To Verify Code's

Underlying Intent Of Life Safety Performance Under Design Earthquake

Building Analyzed Is A N ineteen Story (18 Story + Basement), 240 Feet Tall Slender Concrete

Tower Located In San Francisco With A Gross Area Of 430,000 Square Feet. Unique Features

Of The Slender Concrete Tower Presented Challenges For Seismic Design. Typically, A 240

Feet Tall Concrete Building In Seismic Zone 4 Would Have A Lateral System That Combines

Shear Walls And Moment Frames. However, Two Architectural Features Made The Use Of

Moment Frames Difficult. First, The 60 Feet Long Open Bays Limited The Number Of

Possible Moment Frames. Second, On The Southeast Side Two Of The Perimeter Columns Are

Discontinued At The 6th Story And Six New Columns Are Introduced That Slope For The

Lowest Six Stories At An Angle Of About 20 Degrees From Vertical. These Sloped Columns

Connect To Transverse Walls Through Horizontal Transfer Elements At The 6th Story And Put

Considerable Gravity-Induced Horizontal Loads On The Lateral System At That Level.

Sap2000 Was Used To Perform Pushover Analysis And Etabs Was Used To Calculate HingeProperties Of Shear Wall And Elastic Analysis. For All Lateral Elements, Cracked Section

Was Assumed With An Effective Stiffness Equal To 50% Of Gross Section.

Pushover Analysis Is A Useful Tool Of Performance Based Seismic Engineering To Study

Post-Yield Behavior Of A Structure. It Is More Complex Than Traditional Linear Analysis,

But It Requires Less Effort And Deals With Much Less Amount Of Data Than A Nonlinear

Response History Analysis. Pushover Analysis Was Performed

On A Nineteen Story Concrete Building With Shear Wall Lateral System And Certain Unique

Design Features. Utilizing The Results From This Analysis, Some Modifications Were Made

To The Original Code-Based Design So That The Design Objective Of Life Safety Performance

Is Expected To Be Achieved Under Design Earthquake.


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Chapter-3 RESPONSE REDUCTION FACTOR

Response reduction factor is the factor by which the actual base shear force

should be reduced ,to obtain the design lateral force.

the response reduction factor reflects the capacity of st ructure to dissipate

energy by inelastic behavior . This process is combined effect of over

strength , redundancy and ductility.

Response reduction factor is also known as ratio of maximum elastic force

to designed force.

Response reduction factor is depended on three factors .over strength factor

ductility factor

redundancy factor.

Over strength factor calculated for yielding of structure at load higher than

the designed load due to various partial safety factors, strain hardening ,

over sized members , confinement of concrete.

Ductility factor is ratio of ultimate displacement or code specified

displacement to the yield displacement.


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been obtained according to

GSDMA guidelines and is added to tank walls according to Westergaard

approach.

TWO MASS IDEALIZATION

Concept proposed in IITK-GSDMA guidelines.

Separated pressure in to impulsive and convective parts.impulsive mass Liquid in lower region of tank behaves like mass

rigidly connected to tank which accelerate along with tank

convective mass liquid in upper region that undergoes sloshing

motion

Analysis of elevated tank under seismic load of fluid structure interaction

has been investigated by added mass approach.

In present work impulsive mass has

A finite element model is used to model the elevated tank system using

SAP2000 software.

Columns and beams in the frame type support system are modeled as

frame elements.


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Description of water tank:

SAP software is used to perform the non linear static

pushover analysis.

The RC beams and columns are modeled as 3-D frame elements with

centerline dimension.

Wall and domes are modeled as shell elements.

Column foundations are assumed to be fixed.

Default hinges are considered for analysis

Flexure moment (M3), axial biaxial moment (P-M2-M3) and axial

compressive shear force (V) hinges are assigned at the face of beam,

column, and bracing respectively using the static pushover analysis.


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SAP software is used to perform the non linear static

pushover analysis.

The RC beams and columns are modeled as 3-D frame elements with

centerline dimension.

Wall and domes are modeled as shell elements .

Column foundations are assumed to be fixed.

Default hinges are considered for analysis

Flexure moment (M3), axial biaxial moment (P-M2-M3) and axial

compressive shear force (V) hinges are assigned at the face of beam,column, and bracing respectively using the static pushover analysis.

Fig shows Pushover analysis procedure :


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Pushover curve of 20m3 water tank:

For 12m

For 16m


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For 20m


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TANK TYPE:INTZ TANK COLUMN SIZE:650MM DIASTAGING HEIGHT 12M COLUMN STEEL: 10 -20mm

STAGING TYPE6 COL

CIRCULAR ZONE IV

FULL EMPTY

TIME PERIOD 0.68 0.51

BASE SHEAR 311 193

DUCTILITY FACTOR 0.86 0.86

REDUNDANCY FACTOR 1.283 1.3

OVERSTRENGTH FACTOR 2.733 4.15

R 2.94 4.65

TANK TYPE:INTZ TANK COLUMN SIZE:650MM DIA

STAGING HEIGHT 16M COLUMN STEEL:12 -20mm

STAGING TYPE6 COL

CIRCULAR ZONE IV

FULL EMPTY


BASE SHEAR 280 174




R 1.57 3.36

TANK TYPE:INTZ TANK COLUMN SIZE:650MM DIA

STAGING HEIGHT 20M COLUMN STEEL:14-20mm

STAGING TYPE6 COL

CIRCULAR ZONE IV

FULL EMPTY


BASE SHEAR 328 233




R 1.3 2.65

Result tables:


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0

50

100

150

200

250

300

350

12m 16m 20m

FULL

EMPTY

0

0.2

0.4

0.6

0.8

1

1.2

1.4

12m 16m 20m

FULL

EMPTY

0

0.5

1

1.5

22.5

3

3.5

4

4.5

5

12m 16m 20m

FULL

EMPTY

Effect of staging ht on r facto :

BaseShear(kN

Staging Height (m)

RedundancyFacto

Staging Height (m)

RFact

Staging Height (m)


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0

0.2

0.4

0.6

0.8

1

1.2

1.4

12m 16m 20m

FULL

EMPTY

0

0.5

1

1.5

2

2.5

3

3.5

12 14 16 18 20

REDUNDANCY FACTOR

OVERSTRENGTH FACTOR

R Factor

0

0.5

1

1.52

2.5

3

3.5

4

4.5

5

12 14 16 18 20

REDUNDANCY FACTOR

OVERSTRENGTH FACTOR

R Factor

TimePeriod(sec

Staging Height (m)

Facto

Staging Height (m)

250m3 (Tank Full)

F

act

Staging Height (m)

250m3 (Empty)


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0

0.5

1

1.5

22.5

3

3.5

0 0.5 1 1.5

REDUNDANCY FACTOR

OVERSTRENGTH FACTOR

R Factor

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 0.2 0.4 0.6 0.8 1 1.2

REDUNDANCY FACTOR

OVERSTRENGTH FACTOR

R Factor

Facto

Time Period (sec)

250m3 (Tank Full)

Facto

Staging Height (m)

250m3 (Empty)


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Conclusion:

The elevated tanks Fundamental time period increases with increase in

tank staging height. Also time period increases with the tank filling

condition.

The critical response occurs in case of full tank conditions. This result may

be due to the fact that the hydrodynamic pressures higher in tank full case

as compared to tank empty.

Base shear decreases as the staging height increases that is due to increase

in Time period and the dispersion of base shear is increased when thepercentage of the filling in the storage tanks are increased.

The response reduction factor is considerably affected by the

fundamental time period of water tanks. It reduces as the fundamental time

period increases.

Estimation of response reduction factor with exact analysis will help in an

economical design.

It is observed that response reduction varies from 2.63 to 4 for tank in full

condition in seismic zone IV.