computer modeling of structure to earthquake load.pdf
TRANSCRIPT
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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
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Newton Equation of Motion
Building codes provide guidelines for: F(t)
Computation method to solve equation Solution interpretation and design
[ ]{ } [ ]{ } [ ]{ }xMxCxKtFMatF
&&& ++=
=
)(
)(
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Earthquake Analysis Procedure
Modal/Ritz Vectors Analysis
Equivalent Lateral Load
Static Pushover Response Spectrum
Linear Time History
Nonlinear Time History
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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.