Computer Modeling of Structure to Earthquake Load.pdf

8/14/2019 Computer Modeling of Structure to Earthquake Load.pdf

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Computer Modeling of

Structure to Earthquake Load

ByJohn Li ([email protected])

Solutions Research Centre


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How Do Earthquake Affect Buildings

Earthquake

Seismic waves Site/soil effects

Soil-structure

interaction

Structural

response


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Ground Motion Parameters

For engineering purposes, three

characteristics of earthquake motion are ofprimary significance:

Amplitude

Frequency content

Duration of the motion


4/26Solutions Research Centre

Newton Equation of Motion

Building codes provide guidelines for: F(t)

Computation method to solve equation Solution interpretation and design

[ ]{ } [ ]{ } [ ]{ }xMxCxKtFMatF

&&& ++=

=

)(

)(



Earthquake Analysis Procedure

Modal/Ritz Vectors Analysis

Equivalent Lateral Load

Static Pushover Response Spectrum

Linear Time History

Nonlinear Time History



Energy Conservation

Energy is the fundamental in dynamic analysis.

For earthquake resistant design, try tominimize the mechanical energy.

Use to evaluate the accuracy of the solution.

Strain

Energy+

Kinetic

Energy=

Mechanical

Energy

Damped

Energy

+Strain

Energy

+Kinetic

Energy

=Work

Done


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Modal Vs Ritz Vectors


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Equivalent Lateral Force Method

)1(

1

nekn

j

jj

iii F

HW

HWF =

=


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Response Spectrum Analysis


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Time History Record

24538-S2486-94020.06 SANTA MONICA - CITY HALL GROUNDS AT 90 DEG

3000 POINTS OF ACCEL DATA EQUALLY SPACED AT .020 SEC. (UNITS: CM/SEC/SEC)

2.321 1.647 .854 -.188 -1.492 -.155 1.559 1.468

1.468 .234 -1.725 -.507 .331 .014 1.031 1.911

1.272 -1.191 -.432 .994 1.705 1.341 -1.266 -1.638 -.495 3.286 4.705 -.057 -2.141 .031 2.391 3.937

3.209 -1.892 -4.787 -.361 4.965 2.778 -.768 -1.933

-3.859 -1.514 .460 -.759 -3.399 -1.470 5.361 .499

-3.190 -2.014 -6.361 -.327 5.597 -.284 -6.629 -1.982

3.192 -3.786 -5.605 -3.604 -3.588 1.536 1.673 .285

-2.091 -4.786 .461 1.878 6.096 6.154 -.362 -.090

8.028 15.086 9.537 2.588 -3.574 -1.133 2.995 -5.163

-12.471 -9.782 -4.950 -5.719 -9.039 -8.594 -7.362 -5.799

.590 6.948 5.881 1.054 5.206 7.877 .808 -8.184

-11.273 -6.557 -4.386 -5.915 -8.621 -6.395 4.616 11.018

7.740 4.030 7.361 13.319 14.179 13.029 12.126 7.768

1.784 -4.704 -10.645 -15.894 -16.559 -9.928 -4.541 3.332

10.073 5.642 1.994 5.629 6.987 3.263 -6.605 -14.153 -9.129 .915 .638 -7.667 -9.769 -11.986 -8.324 -4.435

-7.603 -8.013 -5.754 3.932 17.271 17.645 5.381 2.855

5.636 6.088 3.796 2.630 6.783 8.365 5.489 2.831


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Time History Function


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Time History Analysis


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Time History Trace


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Time History Video


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Nonlinear Time History Analysis

Full nonlinear behavior may be considered in a time-history analysis using direct integration. P-delta effects,

large-displacements, and material nonlinearity areavailable. Arbitrary loading may be applied. Applicationsinclude seismic loading, dynamic pushover, andinstability analysis. Most commonly used implicitintegration schemes are available, as well as high-speedexplicit integration for wave propagation, blast, andcollapse problems. Nonlinear direct-integration time-

history analysis cases can be chained together with othernonlinear time-history or static cases (including stagedconstruction), to address a wide range of applications.


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Nonlinear NLLink Element

Linear

Damper Gap

Hook Plasitc1

Isolator1 Isolator2


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Nonlinear Time History


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Energy Plots


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Pushover Curve

M3 Major Moment

P Axial

PMM Axial & Bi-Axial Moments

S Shear


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Pushover Hinge Types

M3 Major Moment

P Axial PMM Axial & Bi-Axial Moments

S Shear


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Pushover Analysis Case


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Hinge Formation


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Pushover Curve


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The Reality!!

Dynamic Testing and Modelling of Existing Buildings in Hong Kong by Dr

Ray Su, Prof Adrian Chandler, Prof Peter Lee, Dr Alex To & Mr J H Li.

1.5401.7892.1232.3362.835Torsion

TRB Building0.8601.1481.4011.3021.588Y Trans

BSB Building

0.5780.6610.7271.2871.622Y Trans

TTT Building

321

Test

Result

ModificationsBare

Frame

Vibration Period (second)

Vibration

Mode


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Power Spectral Density Analysis

Power-spectral-density analysis is available to determinethe probabilistic response of a structure due to cyclic

(harmonic, sinusoidal) loading over a range offrequencies. This is useful for fatigue studies, randomresponse due to earthquakes, and other applications.Multiple loads may be applied at different phase angles,

and may be correlated or uncorrelated. The structuremay be damped or undamped. Frequency-dependentstiffness and damping (complex impedance) propertiesmay be included for modeling foundations and far-fieldeffects, including radiation damping. Power-spectral-density curves may be plotted for any response quantity,and the integrated expected value is automaticallycomputed.

Documents

Computer Modeling of Structure to Earthquake Load.pdf