Base Isolation
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Transcript of Base Isolation
© 2005 IST Group. All rights reserved
Seismic Isolation Project for Seismic Isolation Project for Mitchell HallMitchell Hall
Supervised by:Prof. Dr. Oral Büyüköztürk
Graduate Students:Leonardo Duenas
John KellyTai Chieh Wu
May 2001
© 2005 IST Group
PRESENTATION OVERVIEW
PART 1INTRODUCTION, INVESTIGATION, REHABILITATION OPTIONS
PART 2ANALYSIS OF EXISTING FIXED BASE STRUCTURE
PART 3DESIGN OF BASE ISOLATION
PART 4 ANALYSIS OF ISOLATED STRUCTURE
COMPARISON (PART 2)
PART 5 REALISATION
CONSTRUCTION SEQUENCE AND COST ESTIMATION
© 2005 IST Group
MMISSION ISSION SSTATEMENTTATEMENT
To repair and retrofit Mitchell Hall for seismic upgrade.
It is required that it remain SERVICEABLE - 100 year period of returnand INTACT – 475 period of return.
Superstructure restored aesthetically and functionally.
© 2005 IST Group
BBUILDING UILDING DDESCRIPTIONESCRIPTION
• 30 x 15 m footprint
• Exterior walls : 0.6 m thick un-reinforced concrete
• Columns : Concrete encased I-Sections
• Floor Slabs : Structural slabs resting on mild steel beams
© 2005 IST Group
IINVESTIGATIONNVESTIGATION
Visual InspectionInitial assessment of internal and external members/surfaces
Non-Destructive TestingDetection of faults not visible to the naked eye
Voids, DiscontinuitiesMeasure of material propertiesExtent of internal crack propagation
Historical Research and Analysis Supported by Photographic records
© 2005 IST Group
PPREVIOUS REVIOUS SSEISMIC EISMIC AACTIVITYCTIVITY
Magnitude 7.4 on the Richter Scale, near Izmit, at 15.9 km depth, August 1999
Multiple shocks; 125 – 200 km surface rupture, up to 4.9m right lateral offset, up to 2m vertical offset
Tectonic subsidence or landsliding (in addition to liquefaction and settlement)
Urban earthquake
- fault displacements beneath buildings and bridges
© 2005 IST Group
RREHABILITATION EHABILITATION OOPTIONSPTIONS
Structural Stiffening vs. Base IsolationStructural Stiffening vs. Base Isolation
© 2005 IST Group
SSTRUCTURAL TRUCTURAL SSTIFFENINGTIFFENING
• Cement Injections
• Use of Composite Materials to improve existing
infrastructure
e.g. Composite wrapping/confinement of columns
• Conduit tying (Building Confinement)
• Installation of Shear Walls
• Post Tensioning of external walls
• Gunite / Shotcrete
• Diagonal Bracing Systems
© 2005 IST Group
CCONCRETE ONCRETE RREPAIR EPAIR MMETHODSETHODS
Grout Injections in a Grout Injections in a structural floor slab.structural floor slab.
Wrapping of concrete Wrapping of concrete column with composite column with composite materialmaterial
© 2005 IST Group
CCONCRETE ONCRETE RREPAIR EPAIR MMETHODSETHODS
Use of Shear Walls to resist induced Use of Shear Walls to resist induced seismic loadingseismic loading
© 2005 IST Group
SSTRUCTURAL TRUCTURAL SSTIFFENING TIFFENING
Post-Tensioning Internal Outriggers=>Stiffening System
Ground-Anchors
Induced Moments
3 ft thickmasonry wall (unreinforced)
Building Section
© 2005 IST Group
SSTRUCTURAL TRUCTURAL SSTIFFENING TIFFENING •Advantages
-Most economic and widely used method in Europe.
-Involves repair of existing infrastructure.
e.g. Composite wrapping of columns
Shotcrete walls
•Disadvantages-Involves major intrusion upon existing infrastructure.
-May not be a sufficient solution in itself.
-Restricted building access during construction.
-Irreversible.
© 2005 IST Group
BBASEASE IISOLATIONSOLATION
Concept - Isolate the superstructure from the foundation.Two ways to approach - Install rubber bearings or friction sliding system
© 2005 IST Group
BBASEASE IISOLATIONSOLATION
σ σσf
σf
σf
σy
εy εu
A AA*
εε ε
Elastic strategy Plastic strategy Base Isolation
© 2005 IST Group
BBASEASE IISOLATIONSOLATION
Advantages- Isolates Building from ground motion.
=> Minimal repair of superstructure
- Building can remain serviceable throughout construction.
- Does not involve major intrusion upon existing superstructure.
Disadvantages- Costly. Is challenging to implement in an efficient manner.
- Costly to connect utilities to building (flexible connections).
- Must allow for building displacements.
© 2005 IST Group
PRESENTATION OVERVIEW
PART 1INTRODUCTION, INVESTIGATION, REHABILITATION OPTIONS
PART 2ANALYSIS OF EXISTING FIXED BASE STRUCTURE
PART 3DESIGN OF BASE ISOLATION
PART 4 ANALYSIS OF ISOLATED STRUCTURE
COMPARISON (PART 2)
PART 5 REALISATION
CONSTRUCTION SEQUENCE AND COST ESTIMATION
© 2005 IST Group
FUNDAMENTAL PERIOD
Ct = Coefficient of structural systemhn = Height [m]
Ct = 0.018 Weak seismic resistance
System
hn = 15 m Height
From the bottom of top floor
Ta = 0.1372 s
4/3* nta hCT =
© 2005 IST Group
BASE SHEAR FORCE
Z = Seismic Zone Factor S = Site coefficientI = Importance coefficient W = Seismic dead load
S = 1.2 Medium-dense to dense soil
C = 2.75
I = 1 Special ocupation
Z = 0.4 Seismic zone factor
Rw = 4 Shear walls masonry
M = 1,800,000 kg Seismic load
Vs = 4,950 kN
3/2*25.1
TSC =W
RCIZV
ws ***
=
© 2005 IST Group
WIND LOAD
F = Wind Force [kN] qs = Dynamic wind pressureCq = Pressure Coefficient Iw = Importance factorCe = Coefficient of exposure Ae = Effective area
qs = 0.786 kN/m2 10 - 20 m Height range
130 kph Wind Velocity
Ae = 450 m2 30 m Length
15 m HeightCq = 1.2 Prismatic structure
H <= 2b
Ce = 1.73 Exposure D
Iw = 1 Special occupancy structures
F = 734 kN
ewsqe AIqCCF ****=
© 2005 IST Group
Station Peak Ground Acceleration Max-Horizontal Max-Vertical
ARÇELÝK(ARC)
AMBARLI(ATS)
BOTAÞ (BOT)
ÇEKMECE(CNA)
HAVA ALANI(DHM)
YAPI KREDÝ(YKP)
YARIMCA(YPT)
FATÝH (FAT)
HEYBELÝADA(HAS)
BURSA (BUR) 100.891 mg
57.678 mg
55.115 mg
27.100 mg
241.089 mg
131.714 mg
143.494 mg
48.218 mg
41.07 mg
322.205 mg
189.392 mg
110.230 mg
98.877 mg 23.560 mg
177.307 mg
90.210 mg
211.365 mg 83.252 mg
252.564 mg 80.078 mg
© 2005 IST Group
[North - South] Yarimca Sacaled Record
-500
-400
-300
-200
-100
0
100
200
300
-20 0 20 40 60 80 100 120 140
Seconds
mg
© 2005 IST Group
FFT N-S
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
22000
0 2 4 6 8 10 12 14 16
Frequency [Hz]
Am
plitu
de [
H(w
) ]
© 2005 IST Group
[Vertical] Yarimca Sacaled Record
-400
-300
-200
-100
0
100
200
300
400
-20 0 20 40 60 80 100 120 140
Seconds
mg
© 2005 IST Group
FFT UP
0
2000
4000
6000
8000
10000
12000
14000
16000
0 2 4 6 8 10 12 14 16
Frequency [Hz]
Am
plitu
de [
H(w
) ]
© 2005 IST Group
PRESENTATION OVERVIEW
PART 1INTRODUCTION, INVESTIGATION, REHABILITATION OPTIONS
PART 2ANALYSIS OF EXISTING FIXED BASE STRUCTURE
PART 3DESIGN OF BASE ISOLATION
PART 4 ANALYSIS OF ISOLATED STRUCTURE
COMPARISON (PART 2)
PART 5 REALISATION
CONSTRUCTION SEQUENCE AND COST ESTIMATION
© 2005 IST Group
THEORY OF BASE ISOLATION SYSTEM
Base Isolation system can be modifiedas a 2-DOF system
Kb, Cb
Mb
M
Ks, Cs
Us+Ub+Ug
Ub+Ug
Ug
© 2005 IST Group
THEORY OF BASE ISOLATION SYSTEM (Cont.)
Governing Equation:
)(.......
bgsss uumkuucum +−=++
1.000
Us
1.000
Us
First Mode Second Mode
© 2005 IST Group
DEFINE GUIDELINES
OBTAIN PROPERTIES
ESTIMATE DESIGN
PARAMETERS
SET UP TARGET BUILDING PERIOD AND
BUILDING DISPLACEMENT
COMPUTE EFFECTIVE
STIFFNESS & BASE SHEAR BACK
CALCULATE AND CHECK RESULT
SELECT OPTIMAL
ISOLATORS
PRELIMINARY DESIGN PROCEDURE
© 2005 IST Group
PRELIMINARY DESIGN
References: Uniform Building Code (UBC), 1997 Edition.Design of Seismic Isolated Structures, J. M. Kelly, 1999.
Two Approach to Seismic Hazard:Design Basis Earthquake (DBE)Maximum Capable Earthquake (MCE)
Isolation Design Data:Building Weight : 1,800,000 (Kg) = 4,000 (Kips)Estimate All Dynamic Parameters
© 2005 IST Group
DEFINE GUIDELINES
OBTAIN PROPERTIES
ESTIMATE DESIGN
PARAMETERS
SET UP TARGET BUILDING PERIOD
AND BUILDING DISPLACEMENT
COMPUTE EFFECTIVE
STIFFNESS & BASE SHEAR BACK
CALCULATE AND CHECK RESULT
SELECT OPTIMAL
ISOLATORS
PRELIMINARY DESIGN Procedure
© 2005 IST Group
DESIGN RESPONSE SPECTRA
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Period (sec)
Spec
tral
Acc
erla
tion
(g)
Ca/T
To Ts
Fixed-Based Period
Design Period
Target Building Period : TD = 2.5 (s)TM = 3.0 (s)
© 2005 IST Group
PRELIMINARY DESIGN PROCEDUREDEFINE
GUIDELINES
OBTAIN PROPERTIES
ESTIMATE DESIGN
PARAMETERS
SET UP TARGET BUILDING PERIOD AND
BUILDING DISPLACEMENT
COMPUTE EFFECTIVE
STIFFNESS & BASE SHEAR BACK
CALCULATE AND CHECK RESULT
SELECT OPTIMAL
ISOLATORS
© 2005 IST Group
DDESIGN DATAESIGN DATA
Effective Stiffness & Base Shear Keff = 70 kips/in (12,000 kN/m)Base Shear Below Interface = 940 kips (4200 kN)Above Isolation Interface = 470 kips (2100 kN)
Loading Condition:80% of the weight – Taken by the external wall20% of the weight – Taken by the internal columns
Design Parameters:Max. Displacement – 18 in. (46 cm)Effective Stiffness – average 3 kips/in (500 kN/m) per isolator
© 2005 IST Group
PRELIMINARY DESIGN PROCEDUREDEFINE
GUIDELINES
OBTAINPROPERTIES
ESTIMATE DESIGN
PARAMETERS
SET UP TARGET BUILDING PERIOD AND
BUILDING DISPLACEMENT
COMPUTE EFFECTIVE
STIFFNESS & BASE SHEAR BACK
CALCULATE AND CHECK RESULT
SELECT OPTIMAL
ISOLATORS
© 2005 IST Group
DETAIL OF ISOLATORS
Information Resources : DIS Incorporated Description – Select same size of IsolatorsDiameter : 29.5 (in)Height : 18 (in)
Isolator Properties C29.5-18-L0-S C29.5-18-L1-SDisplacement (in) 20 20
Effective Stiffness (kips/in) 2.2 3.5Energy Dissipation per Cycle (kips-in) 0 1520
Damping Ratio β 0.02 0.23Load Capacity (kips) 230 223
Numbers 16 8
© 2005 IST Group
PRELIMINARY DESIGN PROCEDUREDEFINE
GUIDELINES
OBTAIN PROPERTIES
ESTIMATE DESIGN
PARAMETERS
SET UP TARGET BUILDING PERIOD AND
BUILDING DISPLACEMENT
COMPUTE EFFECTIVE
STIFFNESS & BASE SHEAR BACK
CALCULATE AND CHECK RESULT
SELECT OPTIMAL
ISOLATORS
© 2005 IST Group
PRESENTATION OVERVIEW
PART 1INTRODUCTION, INVESTIGATION, REHABILITATION OPTIONS
PART 2ANALYSIS OF EXISTING FIXED BASE STRUCTURE
PART 3DESIGN OF BASE ISOLATION
PART 4 ANALYSIS OF ISOLATED STRUCTURE
COMPARISON (PART 2)
PART 5 REALISATION
CONSTRUCTION SEQUENCE AND COST ESTIMATION
© 2005 IST Group
PRESENTATION OVERVIEW
PART 1INTRODUCTION, INVESTIGATION, REHABILITATION OPTIONS
PART 2ANALYSIS OF EXISTING FIXED BASE STRUCTURE
PART 3DESIGN OF BASE ISOLATION
PART 4 ANALYSIS OF ISOLATED STRUCTURE
COMPARISON (PART 2)
PART 5 REALISATION
CONSTRUCTION SEQUENCE AND COST ESTIMATION
© 2005 IST Group
BASEMENT EXCAVATION
Dig out basementInsert retaining walls
Prevents excessivebearing
© 2005 IST Group
MOAT EXCAVATION
Insert Lateral Supports
Place Ring BeamsLateral constraintLongitudinal ConstraintProvide for connectiondetailing
© 2005 IST Group
PROVISION OF RIGID LAYERA rigid layer is required directly above and below the soft (isolation) layer.Insert hydraulic jacks
© 2005 IST Group
SITE LOGISTICS4.5 ft
57 ft
50 ft
100 ft
105 ft
Isolator unit
Section from W est side to enable access
R ails
D esired Location
C rane
C ut C olum ns
© 2005 IST Group
INSTALLATION TEAMSTEAM TASK
Demolition: Concrete cutting, and chipping from columns to expose steel (2 days)
Steel: Welding/bolting of collars and corbels to columns /walls to facilitate jacking, and setting up of temporary bracing system (1 – 3 days)
Jacking: Operation of jacks and maintaining correct pressure distributionover building (1/2 day)
Craning: Lower isolators into building and manipulate into place (1 – 3 days)
Grouting: Connect the isolators to the building as specified by manufacturers (1 – 2)
Concrete: Finish on cut outs and columns, ensure good connection and stability against future cracking. (1 – 2 days)
© 2005 IST Group
FLAT JACKING THE ISOLATORS
••Standard jacksStandard jacks
••Oil transfusion jacksOil transfusion jacks
© 2005 IST Group
COST DISTRIBUTION
20%
10%
10%36%
14%
10%
Isolators
Excavation
Demolition
Instalation
Structuralimprovement
Sundries$1,269,050$1,269,050
(New Structure – US$4,000,000)
© 2005 IST Group
Low Cost Strategies
WallsColumns
Matrix of Rubber bearings Connecting beams
Longitudinal rubber bearings in matrix configuration
© 2005 IST Group
Low Cost Strategies
Continuous phase(Matrix)
Interphase
Dispersed phase(Reinforcement)
Multidirectional continuous fiber composite
Composite plates
Reinforcing scheme
© 2005 IST Group
Low Cost Strategies
Set of independent isolators
Columns in charge of single floors.
Internal space is never restricted at any floor
Columns placed in the same external or internal wall-axes
Load distribution to independent sets of isolatorsLocal Fabrication
© 2005 IST Group
BBASEASE IISOLATIONSOLATION (Ball System)(Ball System)mg
2r
N N N
Rigid ballSpherical groove
mg
P
F F
N N
© 2005 IST Group
BBASEASE IISOLATIONSOLATION
Universal Linear SliderHigh Damping Rubber
Synthetic Rubber Bearings