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SACS Dynpac
Dynpac RELEASE 6
USERS MANUAL
ENGINEERING DYNAMICS, INC.
2113 38TH STREET
KENNER, LOUISIANA 70065
U.S.A.
No part of this document may bereproduced in any form, in
anelectronic retrieval system orotherwise, without the prior
written permission of the publisher.
Copyright 2005 by
ENGINEERING DYNAMICS, INC.
Printed in U.S.A.
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TABLE OF CONTENTS
1.0 INTRODUCTION
1-1.......................................................................................................................1.1
OVERVIEW
1-1.........................................................................................................................1.2
PROGRAM FEATURES
1-1......................................................................................................
2.0 DYNAMIC MODELING AND INPUT
2-1.....................................................................................2.1
RETAINED DEGREES OF FREEDOM
2-1.............................................................................2.2
STRUCTURAL MASS
2-2........................................................................................................
2.2.1 Generating Structural Mass Automatically
2-2.................................................................2.2.1.1
Default Structural Density
2-2.................................................................................2.2.1.2
Overriding Structural Density
2-2............................................................................
2.2.2 Converting Loads to Mass Automatically
2-3...................................................................2.2.2.1
Designating Load Cases to Convert to Mass
2-3.....................................................2.2.2.2
Factoring Load Cases
2-4.........................................................................................
2.2.3 User Input Joint Weight
2-4..............................................................................................2.2.4
Structural Mass Contingency Factors
2-4..........................................................................
2.3 FLUID MASS
2-5.......................................................................................................................2.3.1
Generating Fluid Added Mass Automatically
2-5.............................................................
2.3.1.1 Member Overrides for Fluid Added Mass Generation
2-5......................................2.3.1.2 Plate Overrides
for Fluid Added Mass Generation
2-5............................................
2.3.2 Generating Fluid Entrapped Mass Automatically
2-6.......................................................2.3.2.1
Member Overrides for Fluid Entrapped Mass Generation
2-6................................
2.4 HYDRODYNAMIC MODELING USING SEASTATE
2-6.....................................................2.5
SIMULATING NON-LINEAR FOUNDATIONS
2-6...............................................................
2.5.1 Including Linearized Foundation Automatically
2-7........................................................2.6
INCLUDING P-DELTA EFFECTS
2-7.....................................................................................
3.0 DYNPAC INPUT FILE
3-1..............................................................................................................3.1
INPUT FILE SETUP
3-1............................................................................................................3.2
INPUT LINES
3-1......................................................................................................................
4.0 DYNPAC TROUBLE SHOOTING
4-1............................................................................................4.1
MODEL STIFFNESS MATRIX
4-1..........................................................................................4.2
MODEL MASS MATRIX
4-1....................................................................................................
5.0 COMMENTARY
5-1........................................................................................................................5.1
STIFFNESS MATRIX REDUCTION
5-1.................................................................................5.2
MASS MATRIX GENERATION
5-2........................................................................................
5.2.1 Consistent Mass Approach
5-2..........................................................................................5.2.2
Lumped Mass Approach
5-3.............................................................................................
5.3 MASS MATRIX REDUCTION
5-3...........................................................................................5.4
CALCULATING RESULTS
5-4................................................................................................5.5
FLUID ADDED OR VIRTUAL MASS
5-4...............................................................................
6.0 SAMPLE PROBLEMS
6-1...............................................................................................................6.1
SAMPLE PROBLEM 1
6-2........................................................................................................6.2
SAMPLE PROBLEM 2
6-12........................................................................................................6.3
SAMPLE PROBLEM 3
6-14........................................................................................................
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SECTION 1
INTRODUCTION
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1.0 INTRODUCTION
1.1 OVERVIEW
The Dynpac program module generates dynamic characteristics
including eigenvectorsor natural mode shapes, eigenvalues or
natural periods and modal internal load and stressvectors for a
structure.
Because the Dynpac module provides the mode shapes and masses
required for modaldynamic analysis, its execution is required prior
to execution of any of the SACSdynamic programs.
1.2 PROGRAM FEATURES
Dynpac requires a SACS input model file or output structural
data file and a Dynpacinput file for execution. The program creates
a common solution file containingnormalized mode shapes,
frequencies, internal loads etc. and a mass file.
Some of the main features and capabilities of Dynpac program
module are:1. Full six degree of freedom modes supported.2. Guyan
reduction of non-inertially loaded (slave) degrees of freedom.3.
Generates structural mass and fluid added or virtual mass
automatically.4. Supports lumped or consistent mass generation.5.
User input lumped or consistent mass capability.6. Ability to
convert model input loading to mass.7. Utilizes hydrodynamic
properties and modeling from Seastate module.8. Plate and beam
element structural density overrides.9. Member and member group
fluid added mass property overrides.10. Determines modal mass
participation to allow determination of number of modes
required for subsequent dynamic analyses.11. Ability to override
plate added mass coefficient.12. Ability to override plate
properties by plate group.13. Includes P-Delta capabilities in
addition to cable elements.
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DYNPAC MODELING AND INPUT
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2.0 DYNAMIC MODELING AND INPUT
The Dynpac program requires a SACS model file or output
structural data file and aDynpac input file. The model file must
contain minimal additional dynamic modelinginformation in order to
perform the Dynpac analysis, namely, the dynamic analysisoption DY
must be specified in columns 19-20 on the OPTIONS input line,
jointretained (master) degrees of freedom (DOF) must be specified
in the joint fixity columnson the appropriate JOINT input line(s)
and a LOAD header must exist in the modelfile even if no loading is
specified.
2.1 RETAINED DEGREES OF FREEDOM
Dynpac uses a set of master (retained) degrees of freedom,
selected by the user, toextract the Eigen values (periods) and
Eigen vectors (mode shapes). All stiffness andmass properties
associated with the slave (reduced) degrees of freedom are included
inthe Eigen extraction procedure. The stiffness matrix is reduced
to the master degrees offreedom using standard matrix condensation
methods. The mass matrix is reduced to themaster degrees of freedom
using the Guyan reduction method assuming that the stiffnessand
mass are distributed similarly. All degrees of freedom which are
non-inertial (nomass value) must be slave degrees of freedom. After
modes are extracted using themaster degrees of freedom, they are
expanded to include full 6 degrees of freedom for alljoints in the
structure. The expanded modes are used for subsequent dynamic
responseanalysis.
Any joint degree of freedom, X, Y and Z translation and/or
rotation, to be retained forextraction purposes must be designated
in the model. A joint DOF may be retained byspecifying a 2 in the
appropriate fixity column on the JOINT input line. Specifying a0 or
leaving the fixity field blank designates the DOF as a slave degree
of freedom tobe reduced. For example, to retain the X and Z
translation degrees of freedom, specify202 or 2 2 in columns 55-57
on the JOINT line defining the joint.
Note: Columns 55, 56 and 57 pertain to global X, Y and Z
translationrespectively and columns 58, 59, and 60 to X, Y and Z
rotationrespectively.
Support degrees of freedom require no special modeling for
dynamic purposes.
Note: Specifying a 2 or 0 for a particular DOF, has no effect
forstatic analysis.
In dynamic analysis, to accurately calculate the effects of a
concentrated mass along thelength of a member it is best to include
a joint at that location. Also, if a local mode dueto the
concentrated mass is important to the analysis, then the model
should includeretained degrees of freedom at the joint at the
location of the mass. In this way thedynamic analysis will use mass
which is distributed in a manner that matches the massdistribution
of the model.
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2.2 STRUCTURAL MASS
2.2.1 Generating Structural Mass Automatically
By default, Dynpac generates structural mass for modeled beam,
plate and shell elementsautomatically. Structural masses are also
generated if SA is specified as one of theexecution options in
columns 63-68 on the DYNOPT line. Structural masses are
notgenerated if option SO is specified in columns 63-68.
Structural mass may be calculated as lumped or consistent mass
by specifying LUMPor CONS in columns 15-18 on the DYNOPT line
respectively. The lumped methodplaces all element mass at the nodes
to which the element is connected while theconsistent approach
assumes mass is distributed along the element. Although, the
defaultmethod is lumped, consistent mass may be desirable for
structures immersed in fluid.
The following example indicates that the mass of modeled
elements is to be calculatedby the program in addition to
converting some load cases in the model file to mass. Theconsistent
mass approach is to be used.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
DYNOPT CONS SA-Z
Note: Because the lumped approach does not generate mass moments
ofinertia, the weight moment of inertia for each rotational
DOFretained must be specified in the Dynpac input file when using
thelumped approach.
2.2.1.1 Default Structural Density
For a beam element, the density specified on the GRUP input line
is used as the defaultwhen generating structural mass
automatically, unless density is specified on theMEMBER line. If
structural mass is not specified the density specified on theDYNOPT
line is used.
The density specified on the PGRUP or PLATE input lines located
in the model file areused for plate elements. For shell elements on
the other hand, the density specified incolumns 19-25 on the DYNOPT
line is used. The density specified on the SHELL lineis ignored by
the Dynpac program module.
2.2.1.2 Overriding Structural Density
The density for individual members, plates, plate groups, shells
and member groups maybe overridden for mass generation purposes.
The member, plate, shell or group name,along with the structural
density override, are specified in the Dynpac input file on
theMBOVR, PLOVR, PGOVR, SHOVR and GROVR override lines,
respectively.
The following example specifies that the density of member
101-157, member groupMM1, plate A101 and plate group PG1 is to be
100.0 for the purpose of determining thedynamic
characteristics.
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812345678901234567890123456789012345678901234567890123456789012345678901234567890
MBOVR 101 157 100.0GROVR MM1 100.0PLOVR A101 100.0PGOVR PG1
100.0
2.2.2 Converting Loads to Mass Automatically
Loading contained in the SACS model file can be converted to
structural joint ormember mass automatically by specifying SA as
one of the execution options incolumns 63-68 on the DYNOPT input
line.
The direction of loads to be converted and whether the same sign
or the opposite sign ofthe load is to be used when converting to
mass must also be specified in the executionoptions. If loading in
the model file defined in the X direction is to be converted to
mass,then X should be specified. To convert loading defined in the
Y or Z directions, Yor Z should be specified as one of the
execution options respectively. The sign of theload direction
specified, denotes whether the mass calculated from the load line
will havethe same sign as the load, designated by +, or the
opposite sign of the load designatedby -. For example, when
converting loading in the global -Z direction (such as
gravityloading) to mass, the mass should have the opposite sign as
the load specified (ie.positive mass). Therefore, execution options
SA-Z (or SO-Z) should be specified onthe DYNOPT input line.
The following example indicates that the mass of modeled
elements is to be calculatedby the program in addition to
converting load cases in the Z direction in the model file tomass.
The sign of the mass will be the opposite of the sign of the
load.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
DYNOPT CONS SA-Z
Note: When converting loading to mass, the sign of the net load
for anyload vector must be such that no negative mass is
introduced.
2.2.2.1 Designating Load Cases to Convert to Mass
When loads specified in the SACS model file or Seastate input
file are to be converted tomass, only load cases specified on the
LCSEL line(s) designated as dynamic load cases(ie. function DY) are
converted. For example, the following designates that load cases4
and 5 are to be converted to mass by the program.
Note: Either the SA or SO options must be specified on the
DYNOPTline in order to convert the designated load cases to
mass.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
LCSEL DY 4 5
Note: It is recommended to generate structural mass of the
modeledstructure automatically rather than converting the gravity
loadingcreated by Precede or Seastate.
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2.2.2.2 Factoring Load Cases
Load Cases may be factored when converting to mass using the
LCFAC line in theSeastate or model input file. In order to factor a
load case, specify the load case andfactor on the LCFAC using
option DY. For example, the following designates that 50%of load
cases 4 and 5 are to be converted to mass.
Note: Load cases 4 and 5 are specified on the LCSEL and LCFAC
lines.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
LCSEL DY 4 5LCFAC DY 0.50 4 5
2.2.3 User Input Joint Weight
Joint weights not defined in load cases designated to be
converted to mass, may bespecified as user defined concentrated
joint weights in the Dynpac input file.Concentrated joint weights
for X, Y and Z translational degrees of freedom and weightmoments
of inertia for the X, Y and Z rotational degrees of freedom are
specified alongwith the joint name on the JTWGT line and are
converted to masses automatically.
The following designates that X,Y and Z weight of 10.0 is to be
applied at joints 601 and603.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
JTWGT 601 10.0 10.0 10.0JTWGT 603 10.0 10.0 10.0
2.2.4 Structural Mass Contingency Factors
Any mass generated by Dynpac or supplied as a load case in a
SACS input file may begiven a contingency factor via the DYNOP2
line. The contingency factor is amultiplier used to increase or
decrease the affect of the mass on structural loading.
Thecontingency factor for structural mass generated by Dynpac is
entered in columns 8-13;the contingency factor for masses entered
as SACS load cases is entered in columns14-19.
The DYNOPT line in the following example specifies that loading
in the -Z directionwill be converted to structural mass. The DYNOP2
line specifies that Dynpacgenerated mass is to be given a
contingency factor of 25% (1.25) whereas mass obtainedfrom SACS
loading in the -Z direction is to be given a contingency factor of
10% (1.10).
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
DYNOPT CONS SA-ZDYNOP2 1.25 1.10
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2.3 FLUID MASS
2.3.1 Generating Fluid Added Mass Automatically
For structures immersed in fluid, the added or virtual mass and
the mass of entrappedfluid can be generated automatically. By
default, the fluid mass, mudline elevation andthe water depth are
read from the model file or from the Seastate input data. If this
datahas not been previously specified in the model, it must be
specified on the DYNOPT line(in the Dynpac input file) in columns
26-32, 33-39 and 40-46, respectively. The normaland axial added
mass coefficients for members surrounded by fluid are input in
columns49-53 and 54-58 on the DYNOPT line.
Note: Values specified for fluid mass, mudline elevation and
water depthwill override any values input in the model file or in
Seastateinput data.
By default, the virtual mass is calculated based on the added
mass coefficient in columns49-53 on the DYNOPT line and actual
member diameter unless an effective diameter isspecified in columns
73-78 on the MEMBER input line. For plate elements, the virtualmass
is determined using the added mass coefficient specified in columns
49-53 unless avalue is indicated in columns 59-62 on the DYNOPT
line.
The following specifies that the default added mass coefficient
is 1.0 for beam elementsand 0.01 for plate elements (ie.
effectively ignoring plate mass).
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
DYNOPT CONS 1.0 0.01
2.3.1.1 Member Overrides for Fluid Added Mass Generation
The effective member diameter used for added mass calculation
may be overridden forindividual members or for member groups using
the MBOVR or the GROVR linesrespectively in the Dynpac input
file.
The following overrides the effective diameter of member 101-157
and member groupMM1 to 0.001, thus ensuring that no added mass is
calculated for these members.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
MBOVR 101 157 0.001 GROVR MM1 0.001
2.3.1.2 Plate Overrides for Fluid Added Mass Generation
The added mass coefficent for plates and plate groups may be
overridden using thePLOVR and PGOVR lines, respectively in the
Dynpac input file. The following specifiesthat the plate added mass
coefficent for plate A101 and plate group PG1 is 0.001.
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812345678901234567890123456789012345678901234567890123456789012345678901234567890
PLOVR A101 0.001PGOVR PG1 0.001
2.3.2 Generating Fluid Entrapped Mass Automatically
Entrapped mass is calculated for members designated as flooded
in the model file basedon the actual diameter of the member.
2.3.2.1 Member Overrides for Fluid Entrapped Mass Generation
The flood condition may be overridden for all members on the
DYNOPT line in columns47-48. The flood condition for individual
members or member groups may be changedusing the MBOVR or the GROVR
line images in the Dynpac input file.
The following overrides the flood condition of member 101-157
and member groupMM1 to non-flooded, thus ensuring that no entrapped
mass is calculated for thesemembers.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
MBOVR N 101 157 0.001 GROVR MM1 N 0.001
Note: The flood condition specified on the DYNOPT line overrides
anyexisting flood condition for all members in the model unless
floodcondition is changed with subsequent MBOVR or GROVR lines.
2.4 HYDRODYNAMIC MODELING USING SEASTATE
The Seastate program can be used to account for the hydrodynamic
affects of unmodeledstructural items and/or marine growth. Seastate
updates the member lines to account forthe density and effective
diameter due to marine growth specified on MGROV lines inthe SACS
model or in the Seastate input file. Member density is also updated
to reflectthe effective density based on any density and/or cross
section area overrides specified inthe Seastate input. The
effective member diameter in columns 73-78 on the MEMBERinput line
is updated to account for any local Y and Z force dimension
overridesspecified (in addition to effects of marine growth).
Note: Seastate must be executed with DYN specified in columns
56-58 onthe LDOPT line in the Seastate input file or with
theappropriate option specified in the Executive in order to
generatehydrodynamic properties. The model updates are contained in
theoutput structural data file created. See the Seastate
UsersManual for a detailed discussion.
2.5 SIMULATING NON-LINEAR FOUNDATIONS
Because the dynamic capabilities in the SACS system use linear
theory (ie. modalsuperposition), non-linear foundations must be
represented with a linearly equivalentsystem. The equivalent linear
foundation model must be incorporated into the SACSmodel for the
purposes of dynamic analysis.
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Note: The Pile program module can be used to determine the
length,properties and offsets for equivalent pile stub elements
used torepresent the soil-pile interaction. See the PSI/Pile
programusers manual for a detailed discussion.
2.5.1 Including Linearized Foundation Automatically
The PSI program may be used to generate an equivalent foundation
stiffness matrix orsuper-element to be used to represent the
foundation for dynamic analysis. Theequivalent foundation
super-element may be included as part of the model by specifyingI
in column 9 of the OPTIONS line in the model file or by selecting
the appropriatesuperelement option in the Executive.
2.6 INCLUDING P-DELTA EFFECTS
The Dynpac program can include the effects of P-Delta on the
dynamic characterisitcs ofthe structure. This feature allows the
user to designate reference load case(s)representing static dead
loading on the structure.
In order to include P-delta effects, the reference load cases
must be designated in themodel file or the Seastate input file
using the LCSEL line with the PD option. Forexample, the following
shows that dead loading defined by load cases DEAD, EQPT andAREA
are to be used to determine the P-delta effects on the beam
elements.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
LCSEL PD DEAD EQPT AREA
Load factors may be applied to the reference load cases using
the LCFAC line. Forexample, in the following, 50% of load cases
DEAD EQPT and AREA are used to obtainthe reference axial load.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
LCSEL PD DEAD EQPT AREALCFAC PD 0.5 DEAD EQPT AREA
Note: Dead loads are typically used as P-Delta loads. For
cableelements, the pre-tension load should be designated as the
P-Deltaload.
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DYNPAC INPUT FILE
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3.0 DYNPAC INPUT FILE
3.1 INPUT FILE SETUP
The Dynpac input file contains general dynamic analysis
information and may includeadditional hydrodynamic property
override information. The table below shows thestandard Dynpac file
input lines.
INPUT LINE DESCRIPTION
TITLE Dynamic analysis title
DYNOPT* Dynamic analysis options
DYNOP2 Additional dynamic analysis options
PLOVR Plate override data
PGOVR Plate group override data
GROVR Member group density and hydrodynamic property
overrides
MBOVR Member density and hydrodynamic property overrides
SHOVR Shell element structural weight density overrides
JTWGT Joint concentrated weight data
END* End of input data
Note: Lines that are required are designated with an
asterisk.
3.2 INPUT LINES
The following section illustrates the formats of the input lines
for Dynpac. The usershould be familiar with the basic guidelines
for specifying input data. These guidelinesare located in the
Introduction Manual.
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10111213141516171819202122232425262728293031323334353637383940
DYNAMIC CHARACTERISTICS SAMPLE PROBLEM
ENGLISH UNITS CONSISTENT MASS APPROACH
DYNOPT +ZEN 15CONS
41424344454647484950515253545556575859606162636465666768697071727374757677787980
SA-Z
THE TITLE LINES DYNAMIC CHARACTERISTICS SAMPLE PROBLEM AND
ENGLISHUNITS CONSISTENT MASS APPROACH ARE ENTERED BEFORE THE
OPTIONS LINE.
DESCRIPTIVE TITLE LINES
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DESCRIPTIVE TITLE
2
))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))80
COLUMNS COMMENTARY
LOCATION IF INPUT, THIS OPTIONAL LINE IS FIRST IN THE DYNPAC
INPUT FILE.
GENERAL THIS LINE IS OPTIONAL AND ALLOWS THE USER TO SPECIFY A
TITLE FOR DYNPAC OUTPUT OTHER THAN THE TITLE FROM THE SACS IV
FILE.
( 2-80) ENTER ANY ALPHANUMERIC TITLE. THIS TITLE WILL APPEAR ON
ALL PAGES OF DYNPAC OUTPUT.
DYNPAC TITLE
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DYNAMIC CHARACTERISTICS SAMPLE PROBLEM
ENGLISH UNITS 150' WATER DEPTH
DYNOPT +ZEN 15CONS 62.4 -150.
41424344454647484950515253545556575859606162636465666768697071727374757677787980
150. SA-Z
THE VERT COORDINATE DIRECTION IS +Z AND ENGLISH UNITS ARE TO BE
USEDFOR THE DYNAMIC CHARACTERISTIC ANALYSIS. 15 MODE SHAPES ARE TO
BEEXTRACTED AND THE CONSISTENT MASS APPROACH IS TO USED. THE
MUDLINEELEVATION IS AT -150 AND THE DEPTH TO BE USED FOR VIRTUAL
MASS ANDBUOYANCY CALCULATION IS 150 FEET. LOADS IN THE GLOBAL Z
DIRECTIONSPECIFIED IN THE SACS MODEL FILE ARE TO BE CONVERTED TO
MASS WITH THEOPPOSITE SIGN AS SPECIFIED BY SA-Z IN COLUMNS
63-66.
DYNAMIC ANALYSIS OPTIONS LINE
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LINELABEL
VERT.COORD.
UNITSNO.
MODES
MASSCALC.
OPTION
STRUCT.DENSITY
FLUIDDENSITY
OVERRIDE
MUDLINEELEV
OVERRIDE
WATERDEPTH
OVERRIDE
FLOODOR
NON-FLOODOPTION
ADDEDMASS
COEFF.
AXIALADDEDMASS
COEFF.
PLATEADDEDMASS
COEFF.
EXECUTIONOPTIONS
OUTPUT OPTIONS
1ST 2ND 3RD 1ST 2ND 3RD 4TH 5TH 6TH
DYNOPT
1) 6 8
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DYNAMIC CHARACTERISTICS SAMPLE PROBLEM
ENGLISH UNITS 150' WATER DEPTH
DYNOPT +ZEN 15CONS 62.4 -150.
DYNOP2 1.10 1.25
41424344454647484950515253545556575859606162636465666768697071727374757677787980
150. SA-Z
IN ADDITION TO OPTIONS SPECIFIED ON THE DYNOPT LINE, THIS
SAMPLESPECIFIES ADDITIONAL MODAL ANALYSIS OPTIONS. DYNPAC
CALCULATEDSTRUCTURAL MASSES ARE TO BE GIVEN A CONTINGENCY FACTOR OF
1.10. WHENCONVERTED TO MASS, LOADS IN THE GLOBAL Z DIRECTION
SPECIFIED IN THE SACSMODEL FILE WILL BE GIVEN A CONTINGENCY FACTOR
OF 1.25.
DYNAMIC MODAL ANALYSIS OPTIONS LINE
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WEIGHT CONTINGENCY FACTORS
LEAVE BLANKDYNPACCALCULATEDSTRUCTURAL
MASSES
SACSLOAD
MASSES
DYNOP2
1))))) 6 8
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DYNOPT +ZEN 15CONS
PLOVR AAAAAAAM 225.0
41424344454647484950515253545556575859606162636465666768697071727374757677787980
SA-Z
THE STRUCTURAL DENSITY FOR CERTAIN PLATES IS TO BE OVERRIDDEN
FOR THEPURPOSE OF DETERMINING THE DYNAMIC CHARACTERISTICS OF THE
STRUCTURE.225.0 LB/CU.FT (TONNE/M^3) WILL BE USED AS THE DENSITY OF
PLATES AAAATHROUGH AAAM.
PLATE OVERRIDE
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PLATE RANGESTRUCTURAL
WEIGHT DENSITY
ADDEDMASS
COEFF.LEAVE BLANK
START NAME END NAME
PLOVR
1))) 5 7))))))10 11))))))14 21
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DYNOPT +ZEN 15CONS
PGOVR PMM 225.0
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SA-Z
THE STRUCTURAL DENSITY FOR CERTAIN PLATES IS TO BE OVERRIDDEN
FOR THEPURPOSE OF DETERMINING THE DYNAMIC CHARACTERISTICS OF THE
STRUCTURE.225.0 LB/CU.FT (TONNE/M^3) WILL BE USED AS THE DENSITY OF
PLATESASSIGNED TO GROUP PMM.
PLATE GROUP OVERRIDE
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PLATEGRUPNAME
STRUCTURALWEIGHT DENSITY
ADDEDMASS
COEFF.LEAVE BLANK
PGOVR
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GROVR PL1 0.01
GROVR PL2 0.01
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THE MASS OF THE PILE GROUPS PL1 AND PL2 IS DESIGNATED AS 0.01
SOTHAT NO EFFECTIVE MASS OF THE MEMBERS ASSIGNED TO THESE GROUPS
WILL BECONSIDERED.
MEMBER GROUP MASS DATA OVERRIDE LINE
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GROUPCODE
FLOODED CRITERIAF - FLOODED
N - NON-FLOODED
OUTSIDE DIAMETERFOR
FLUID ADDED MASSCALCULATION
STRUCTURALWEIGHT DENSITY
LEAVE BLANK
GROVR
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MBOVR 101 201 0.01
MBOVR 103 203 0.01
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THE WEIGHT OF DUMMY MEMBERS 101-201 AND 103-203 ARE NOT TO BE
CONSIDEREDFOR THE DYNAMIC CHARACTERISTIC CALCULATION. A WEIGHT
DENSITY OF 0.01 ISTHEREFORE SPECIFIED TO BE USED FOR MEMBER MASS
CALCULATIONS.
MEMBER MASS DATA OVERRIDE LINE
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FLOODED CRITERIAF - FLOODED
N - NON-FLOODED
MEMBER DESIGNATION OUTSIDE DIAMETERFOR
FLUID ADDED MASSCALCULATION
STRUCTURALWEIGHT DENSITY
LEAVE BLANKSTARTJOINT
ENDJOINT
MBOVR
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SHOVR BAAA 225.0
SHOVR CAAACAAM 225.0
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THE STRUCTURAL DENSITY SPECIFIED ON THE DYNOPT LINE IS TO BE
OVERRIDDENFOR THE PURPOSE OF CALCULATING THE MASS OF CERTAIN SHELL
ELEMENTS. ADENSITY OF 225.0 LB/CU.FT (TONNE/M^3) IS DESIGNATED AS
THE DENSITY OFSHELL BAAA AND SHELLS CAAA THROUGH CAAM.
NOTE: THE STRUCTURAL DENSITY SPECIFIED ON THE DYNOPT LINE IMAGE
IS USED AS THE DEFAULT DENSITY OF ALL SHELL ELEMENTS REGARDLESS OF
THE DENSITY SPECIFIED ON THE SHELL LINE IMAGE.
SHELL MASS DENSITY OVERRIDE LINE
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WEIGHT DENSITYLEAVE BLANK
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SHOVR
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JTWGT 354 10.5 10.5 10.5
JTWGT 355 10.5 10.5 10.5
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ADDITIONAL JOINT WEIGHT OF 10.5 KIPS (TONNES) IS TO BE APPLIED
TO JOINTS354 AND 355 IN THE GLOBAL X, Y AND Z DIRECTIONS. THE
WEIGHT WILL BECONVERTED TO TRANSLATIONAL MASS FOR THE X, Y AND Z
DEGREES OF FREEDOM.
JOINT CONCENTRATED WEIGHT LINE
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JOINTNUMBER
JOINT CONCENTRATED WEIGHT DATA
WEIGHT(X DIRECTION)
WEIGHT(Y DIRECTION)
WEIGHT(Z DIRECTION)
WEIGHT MOMENTOF INERTIA
(X AXIS)
WEIGHT MOMENTOF INERTIA
(Y AXIS)
WEIGHT MOMENTOF INERTIA
(Z AXIS)
JTWGT
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END
41424344454647484950515253545556575859606162636465666768697071727374757677787980
THE END LINE DESIGNATES THE END OF INPUT DATA.
END OF DATA
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LEAVE THIS FIELD BLANK
END
1)) 3
4)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))80
COLUMNS COMMENTARY
GENERAL THIS LINE IS THE LAST LINE OF THE INPUT FILE.
( 1- 3) ENTER END.
END LINE
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DYNPAC TROUBLE SHOOTING
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4.0 DYNPAC TROUBLE SHOOTING
4.1 MODEL STIFFNESS MATRIX
As part of the dynamic characteristic analysis, the Solve module
is used to generate thestiffness matrix properties of the
structure. The structural model matrix created by Solvemust be
Positive Definite in order to determine the dynamic characteristics
of thestructure. In general, if a degree of freedom for any joint
or portion of the structure is notrestrained by fixity or by
stiffness from other elements, the matrix will be
Non-PositiveDefinite. For further discussion on matrix Non-Positive
Definite, see the section titledSACS IV Trouble Shooting in the
SACS IV users manual.
The Solve module also determines the accuracy of the solution
and reports it as theMaximum Number of Significant Digits Lost. In
general, solutions with six or fewersignificant digits lost are
sufficiently accurate while solutions with twelve or more lostare
not. The SACS IV userss manual addresses possible causes for
excessive numbersof lost significant digits.
4.2 MODEL MASS MATRIX
The structural mass matrix is developed by the Dynpac program
module. Like thestiffness matrix, the structural mass matrix must
be Positive Definite in order for it tobe inverted. When the mass
matrix can not be inverted, the message Non-PositiveDefinite Mass
Matrix is printed in the listing file. Some common reasons for
thestructural mass matrix becoming Non-Positive Definite are as
follows:
1. No degrees of freedom in the model are retained as master
DOFs. The errormessage will normally refer to a degree of freedom
for joint name 0.
2. All degrees of freedom are either retained or restrained as
master DOFs so thatthere are no slave or unrestrained DOFs.
3. The mass for a particular degree of freedom is negative. This
can occur whenconverting loads specified in the model file to mass
using the SA or SOoption on the DYNOPT line. When negative loads in
the model file are to beconverted, ie. gravity loads, the -X, -Y or
-Z option should be specified sothat the sign of the mass generated
will be positive (opposite to that of the load).
4. A rotational degree of freedom is retained as a master DOF
but no mass momentof inertia was generated (ie. lumped approach) or
no weight moment of inertiawas specified in the input file for that
DOF.
When a matrix Non-Positive Definite occurs, the critical degree
of freedom and thejoint name are reported in the Dynpac listing
file. For additional information ondebugging the model, see the
SACS IV users manual.
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SECTION 5
COMMENTARY
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mm ms
sm ss
K KK
K K
=
m mm ms m
s sm ss s
F K KF K K
dd
=
m mm m ms s
s sm m ss s
F K K
F K K
d dd d
= += +
(1)
sms m
ss
KK
d d= - (2)
sm smm mm m ms m mm ms m
ss ss
K KF K K K K
K Kd d d
= + - = -
(3)
5.0 COMMENTARY
5.1 STIFFNESS MATRIX REDUCTION
The purpose of the Dynpac program module is to generate dynamic
characteristics (modeshapes and frequencies) of a structure. A
Guyan reduction is performed to reduce thestructural stiffness
matrix K created by SACS IV as follows:
where the subscript m designates master degrees of freedom and
the subscript sdesignates slave degrees of freedom. Knowing that F
= Kd or
the following relationships can be made.
If, by definition, no external forces are applied directly to
the slave degrees of freedomsuch that Fs=0, ds can be expressed as
follows:
Substituting for ds in equation (1) yields a relation that can
be used to calculate the external forces onmaster degrees of
freedom, namely,
or
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[ ]m mm mF K d= (3)
( ) ( ), , , , , , , ,a a b b a a b bf x f xd d q d q d d q d q=
=& & & & &
212
KE M dxd= &
for , , ,a b a bd dKE
qdt dq
d d q q
=
& & & &&&
where K'mm is the reduced stiffness matrix. Once the master
degrees of freedom arecalculated, relation (2) may be used to
determine the slave degrees of freedom.
5.2 MASS MATRIX GENERATION
5.2.1 Consistent Mass Approach
The mass matrix may be generated based on the lumped or
consistent mass approach.The consistent mass generation approach
represents the kinetic energy of the distortedelement by the
element joint velocities, as represented by the velocities of all
degrees offreedom at the joint. The deflection d and velocity d'
along a member may be expressedas follows:
The kinetic energy is defined as:
where M is the mass per unit length. Taking
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a
a
b
b
M
dqdq
&&&&&&&&
12
mm ms mm s
sm ss s
M MKE
M Md
d dd
=
&& & &
sms m
ss
KK
d d = -& &
results in
where [M] is the elemental mass matrix for the element. The
elemental mass matrix isthen transformed into the global coordinate
system and added to the overall structuralmass matrix.
Note: Because the consistent approach takes into account
thedistribution of mass along the element, the mass matrix
createdincludes off-diagonal coupling terms between all degrees
offreedom, including rotational DOFs.
5.2.2 Lumped Mass Approach
In the lumped approach, a diagonal mass matrix is created by
dividing each element massinto equal components along the global X,
Y and Z directions and concentrating thesemasses at the end joints.
Rotational mass or mass moments of inertia are neglected alongwith
any off diagonal terms of the mass matrix.
Note: Because off diagonal terms are assumed to be zero in the
lumpedmass approach, it is not recommended when the element mass is
notthe same in all three directions such as when including effects
offluid added or virtual mass acting normal but not tangential
tothe element.
5.3 MASS MATRIX REDUCTION
After the overall mass matrix has been generated by either the
consistent or lumped massapproach, it is partitioned into the same
form as the stiffness matrix such that:
Note: The terms Mms and Msm = 0 and Mmm and Mss are diagonal
matrices forthe lumped approach.
Differentiating equation (2) with respect to time yields,
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{ }12
mm mssmm msm
sm ssmsss
IM MK
KE I KM MK
Kd d
= - -
& &
[ ]{ }12 m mm m
KE Md d = & &
n tF F F= +
( )2
21 1 12 4 4n n nn Dn s rel rel Mn s n Mn s
DF C D V V C D V C V
pr p r r= + + -& &
( )2
21 1 12 4 4t t tt Dt s rel rel Mt s t Mt s
DF C D V V C D V C V
pr p r r= + + -& &
therefore, the equation for kinetic energy becomes
which is a standard Guyan reduction resulting in
where M'mm is the reduced mass matrix.
5.4 CALCULATING RESULTS
Once the reduced stiffness and reduced mass matrices are
generated, theeigenvalues/eigenvectors for the master degrees of
freedom are extracted using thestandard Householder-Givens
extraction technique. The resulting eigenvectors at themaster
degrees of freedom are expanded to obtain results for the reduced
or slavedegrees of freedom which allows the calculation of modal
reactions and modal elementalinternal loads.
5.5 FLUID ADDED OR VIRTUAL MASS
Morrisonss equation is used to determine the hydrodynamic
loading due to fluid addedor virtual mass. The resultant force per
unit length, F, has a component normal to theelement, Fn, and a
component tangential or along the cylinder axis, Ft.
where Fn and Ft are functions of the fluid relative velocity
Vrel, fluid acceleration V' andthe acceleration of the structure
V's, and are given by the following for tubular elements:
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( )
( )
2 2
2 2
14 4
14 4
n
t
n Mn v
t Mt v
D Dm C C
D Dm C C
p pr r
p pr r
= - =
= - =
cos cos cos
sin sin sinnx n x ny n y nz n z
tx t x ty t y tz t z
m m m m m m
m m m m m m
a a a
a a a
= = =
= = =
where the term (Cm-1)(pD2/4)r is the fluid added mass term. The
normal added mass, mn,and axial or tangential added mass, mt, may
be rewritten as follows:
where Cvn and Cvt are the normal and axial added mass
coefficients input into the Dynpacprogram, respectively.
Note: Because the default tangential mass coefficient, Cvt, is
zero,tangential added mass is ignored by default unless the
coefficientis overridden by the user.
The added mass normal to the member and the mass tangential, if
applicable, are brokeninto global X, Y and Z direction masses then
added to the elemental mass matrix.Including the hydrodynamic
inertial terms due to structural acceleration in the massmatrix,
results in the automatic inclusion of acceleration dependent
hydrodynamic forcesincluding relative acceleration effects.
The global X, Y and Z components, mnx, mny and mnz, of the
normal fluid added or virtualmass and the X, Y and Z components of
the tangential fluid added mass, mtx, mty andmtz,are taken as:
where ax, ay and az are the angle between the plane normal to
the element and the globalX, Y and Z axes respectively. See the
following figure.
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SAMPLE PROBLEMS
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Figure 1
6.0 SAMPLE PROBLEMS
The structure shown in Figure 1 was used to illustrate various
capabilities of the Dynpacprogram. Three separate Dynpac analyses
are illustrated:
1. The dynamic characteristics of the structure submerged in
water weredetermined using the consistent mass approach. Seastate
override lines wereused for the hydrodynamic modeling. The
linearized foundation elements wereincluded in the model file.
2. Sample Problem 2 is the same as Sample Problem 1 except that
instead ofmodeling linearized pile stubs, a linearized foundation
superelement was used.The ability to convert loads from any load
case to mass without copying the loadinto LC 1 is also
illustrated.
3. The natural modes of the deck in Figure 1 were determined
using the lumpedmass approach. Additional joint weight was added in
the Dynpac input file.
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6.1 SAMPLE PROBLEM 1
The following example illustrates the use of the Seastate and
Dynpac programs todetermine the dynamic characteristics of a
structure submerged in a fluid.
The structure in Figure 1 stands in 82.02 feet of salt water
(density 64.2 lb/ft3). Themember mass, mass of marine growth, mass
of entrapped water and virtual or addedmass were calculated
automatically using the consistent mass approach. The
Seastateprogram was used to determine the effective member
properties including diameter,density, etc. to account for the
hydrodynamic properties of the members. Additionalmember and group
overrides were specified in the Dynpac input file.
A load case consisting of miscellaneous loads, was specified in
the SAC input file toaccount for unmodeled members and equipment
weights that could affect the dynamiccharacteristics of the
structure.
Dummy piles used to simulate the soil/pile interaction was
developed using the Pileprogram and were added to the model. The
degrees of freedom to be retained fordetermining the generalized
masses and the eigenvectors were designated (usingPrecede) by
specifying a 2 for the joint DOF.
A Seastate input file containing override lines to account for
the hydrodynamics ofunmodeled members and appurtenances was used as
the SACS input file. 50% of loadcase MISC in the model file
contains miscellaneous loads to account for unmodeledmembers and
equipment and is converted to mass.
The following is a portion of the Seastate input file:
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
A LDOPT IN NF+Z 64.20 490.00 -82.02 82.02 DYN NP KB LCSEL DY
MISC C LCFAC DY 0.50 MISCD FILE JE CDM
CDM 11.81 1.000 1.400 1.200 1.400 CDM 23.62 1.000 1.500 1.200
1.500 CDM 47.24 1.000 1.600 1.200 1.600 CDM 70.87 1.000 1.700 1.200
1.700
E MGROVMGROV 0.000 26.247 MGROV 26.247 52.493 0.984 MGROV 52.493
82.021 1.969
E GRPOVGRPOV LG1 F GRPOV PL1 F 0.001 0.001 GRPOV PL2 F 0.001
0.001 GRPOV DK1 0.001 0.001 GRPOV DK2 0.001 0.001 LOADEND
The following is a description of the Seastate input file:
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A. The LDOPT line specifies the physical parameters of the
structure such as waterdepth, water and steel density etc. DYN in
columns 56-58 specifies that aSACS hydrodynamic model is to be
created for use by Dynpac.
B. The LCSEL line designates that if the convert load case to
mass option isspecified in the Dynpac input file, only load case
MISC is to be converted.
C. The LCFAC line indicates that load case MISC is to be
factored by 0.50 whenconverted to mass.
D. The FILE line indicates that only loading in the jacket
geometry file is to beconsidered for this analysis (i.e. J in
column 6).
E. The CDM, MGROV and GRPOV lines ensure that entrapped water
mass andadded or virtual mass are generated accurately.
The following is a portion of the model file used for this
sample followed by adescription of the input:
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1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
A OPTIONS EN DY SDUC 1 1 1 0 PT PTSECTSECT CONDSM TUB 66.26
3032.45 1516.22 1516.22 19.690.551
B SECT PILSTUB PRI 71.86 13490.0 6745.00 6745.00 10.0 10.0
GRUP
C GRUP PST PILSTUB 29.00 11.6 36.0 9 0.01*******************
ADDITIONAL SACS GROUP AND MEMBER Lines *********************
D MEMBER2 2 102 PSTMEMBER OFFSETS 12.5MEMBER2 4 104 PSTMEMBER
OFFSETS 12.5MEMBER2 6 106 PSTMEMBER OFFSETS 12.5MEMBER2 8 108
PSTMEMBER OFFSETS 12.5JOINT
E JOINT 2 -20.505-20.505-88.583 FIXEDJOINT 4
20.505-20.505-88.583 FIXEDJOINT 6 20.505 20.505-88.585 FIXED JOINT
8 -20.505 20.505-88.583 FIXED**************** More Joints
******************************JOINT 309 0.000 0.000 -3.281 JOINT
310 0.000 0.000 -3.281
F JOINT 401 -9.842 -9.842 19.685 222 JOINT 403 9.842 -9.842
19.685 222 JOINT 405 9.842 9.842 19.685 222 JOINT 407 -9.842 9.842
19.685 222 JOINT 409 0.000 0.000 19.685 LOAD
G LOADCNMISCLOAD Z 405 466 2.65750-3.8892 GLOB CONC SKID1 LOAD Z
405 466 17.6575-4.0025 GLOB CONC SKID1 LOAD Z 466 468
24.0806-4.2753 GLOB CONC SKID1 LOAD Z 466 468 2.86744-4.0485 GLOB
CONC SKID1 LOAD Z 467 468 17.0276-4.3356 GLOB CONC SKID1 LOAD Z 467
468 2.02758-4.4489 GLOB CONC SKID1 LOAD Z 401 403 -1.969 -1.969
GLOB UNIF WALK1LOAD Z 472 401 -1.969 -1.969 GLOB UNIF WALK1 LOAD Z
403 465 -1.969 -1.969 GLOB UNIF WALK1 LOAD Z 407 405 -1.969 -1.969
GLOB UNIF WALK1 LOAD Z 405 466 -1.969 -1.969 GLOB UNIF WALK1 LOAD Z
471 407 -1.969 -1.969 GLOB UNIF WALK1 END
The following is a description of the SACS input file:
A. The analysis Dynamic option specified in columns 19-20 on the
OPTIONS line(DY).
B. The dummy pile section properties are defined using section
PILSTUB.
C. The dummy pile group PST is defined.
D. Dummy pile members 2-102, 4-104, 6-106 and 8-108 are
defined.
E. The dummy pile bottom joints 2, 4, 6 and 8 are fixed (joint
fixity FIXED).
F. The retained degrees of freedom are specified by 2 in columns
55-60 on theappropriate JOINT lines. For example, Joint 401 is
retained for translation in theX, Y, and Z directions as designated
by 222 in columns 55-57.
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G. The loads of Load Condition MISC account for the weight of
unmodeledmembers and equipment and will be converted to masses by
Dynpac.
Seastate and Dynpac were executed in succession to determine the
dynamiccharacteristics of the structure. The output structural data
file created by Seastatecontaining the effective member properties
was used as the model input file for Dynpac.
Note: Seastate and Dynpac can be run as separate analysis steps
ortogether as a single step. When executing separately, specify
theSeastate output structural data file as the SACS input file
forthe Dynpac execution.
The following is the Dynpac input file used for this sample
followed by a description ofthe input:
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
TITLE DYNPAC SAMPLE PROBLEM
A DYNOPT +ZEN 10CONS 490. 64.2 -80.2 80.2 NF SA-ZB GROVR PL1 N
1.0
GROVR PL2 N 1.0C MBOVR F 301 401 40.0
MBOVR F 201 301 40.0END
A. The DYNOPT line specifies the following:a. The vertical
coordinate is the +Z direction and English units are to be used
as specified in columns 8-9 and 10-11 respectively.b. 10 modes
are desired (columns 12-14).c. The consistent mass approach is
specified by CONS in columns 15-18.d. The structure and fluid
density are 490.0 and 64.2 lb/ft3 respectively.e. The mudline
elevation (-80.2) and the water depth (80.2) are specified in
columns 33-39 and 40-46 respectively.f. All members without
flood condition designated, are to be considered non-
flooded for the Dynpac analysis as specified by NF (columns
47-48).g. Loads from the SACS data are to be used as masses and the
Z direction
masses will be opposite sign of the specified Z direction load
(SA-Z incolumns 63-66).
B. The GROVR lines specify that groups PL1 and PL2 (the piles
inside the legs)be non-flooded and have an effective outside
diameter of 1 inch for fluid addedmass and entrapped water mass
calculation.
C. The MBOVR lines specify that members 301-401 and 201-301 have
an effectiveoutside diameter of 40.0 inches for fluid added mass
calculation.
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Six of the modes are displayed below. The output file
follows.
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DYNPAC SAMPLE PROBLEM DATE 19-JAN-1993 TIME 08:06:21 DYN PAGE
1
DYNAMIC ANALYSIS PARAMETERS
NO. JOINTS ......... 60 NO. MEMBERS......... 139 NO. PLATES
......... 16 NO. SHELL ELEMENTS.. 0 NO. REDUCED DOF..... 287 NO.
RETAINED DOF.... 73 NO. MODES .......... 10 NO. VECTORS.........
10
EXPANDED MODE SHAPES REQUESTED
MASS PASSED FROM SACS DATA - ADDITIONAL DIRECTION - -Z
AUTOMATIC CONSISTENT MASS OPTION SELECTED
STRUCTURAL DENSITY = 490.00 LB/FT**3 FLUID DENSITY = 64.20
LB/FT**3
FLUID ADDED MASS COEFFICIENT = 1.000
MUDLINE ELEVATION = -80.20 FT WATER DEPTH = 80.20 FT
ALL TUBULAR MEMBERS CONSIDERED BUOYANT UNLESS OTHERWISE
SPECIFIED
PLATE PROPERTIES
NAME ****** JOINTS ****** OFFSET THICKNESS DENSITY 1 2 3 4
(INCHES) (LB/CU FT)
A100 461 462 472 0 0 1.969 490.000 A101 401 472 462 0 0 1.969
490.000 A102 462 463 403 401 0 1.969 490.000 A103 463 464 465 0 0
1.969 490.000 A104 465 403 463 0 0 1.969 490.000 A105 403 465 466
405 0 1.969 490.000 A106 405 466 468 0 0 1.969 490.000 A107 467 468
466 0 0 1.969 490.000
PLATE WEIGHTS X 280.336 KIPS PLATE CG LOC X 0.000 FT Y 280.336
KIPS Y 0.000 FT
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MEMBER PROPERTIES
MEMBER TYPE GRUP FIXITY BUOY DENSITY BETA AREA OD AM-OD
(LB/CUFT) (SQIN) (IN)
101- 102 TUB PL4 311000 YES 490.000 0.00 72.032 29.921 29.860
101- 111 TUB HB1 0 YES 490.000 0.00 37.714 19.685 19.680 117- 101
TUB HB1 0 YES 490.000 0.00 37.714 19.685 19.680 101- 151 TUB DB1 0
YES 490.000 0.00 37.714 19.685 19.680 101- 157 TUB DB1 0 YES
490.000 0.00 37.714 19.685 19.680 101- 201 TUB LG1 0 NO 490.000
0.00 70.341 29.921 30.680 102- 202 TUB PL1 0 YES 490.000 0.00
39.936 23.622 1.000 103- 104 TUB PL4 311000 YES 490.000 0.00 72.032
29.921 29.860 111- 103 TUB HB1 0 YES 490.000 0.00 37.714 19.685
19.680 103- 113 TUB HB1 0 YES 490.000 0.00 37.714 19.685 19.680
103- 151 TUB DB1 0 YES 490.000 0.00 37.714 19.685 19.680 103-
153 TUB DB1 0 YES 490.000 0.00 37.714 19.685 19.680 103- 203 TUB
LG1 0 NO 490.000 0.00 70.341 29.921 30.680 104- 204 TUB PL1 0 YES
490.000 0.00 39.936 23.622 1.000 105- 106 TUB PL4 311000 YES
490.000 0.00 72.032 29.921 29.860 113- 105 TUB HB1 0 YES 490.000
0.00 37.714 19.685 19.680 105- 115 TUB HB1 0 YES 490.000 0.00
37.714 19.685 19.680 105- 153 TUB DB1 0 YES 490.000 0.00 37.714
19.685 19.680 105- 155 TUB DB1 0 YES 490.000 0.00 37.714 19.685
19.680 105- 205 TUB LG1 0 NO 490.000 0.00 70.341 29.921 30.680
106- 206 TUB PL1 0 YES 490.000 0.00 39.936 23.622 1.000 107- 108
TUB PL4 311000 YES 490.000 0.00 72.032 29.921 29.860 115- 107 TUB
HB1 0 YES 490.000 0.00 37.714 19.685 19.680 107- 117 TUB HB1 0 YES
490.000 0.00 37.714 19.685 19.680 107- 155 TUB DB1 0 YES 490.000
0.00 37.714 19.685 19.680 107- 157 TUB DB1 0 YES 490.000 0.00
37.714 19.685 19.680 107- 207 TUB LG1 0 NO 490.000 0.00 70.341
29.921 30.680 108- 208 TUB PL1 0 YES 490.000 0.00 39.936 23.622
1.000 109- 110 TUB CON 311000 YES 490.000 0.00 66.260 19.690
19.650
111- 109 TUB HD1 0 YES 490.000 0.00 24.944 14.961 14.960 113-
109 TUB HD1 0 YES 490.000 0.00 24.944 14.961 14.960 109- 115 TUB
HD1 0 YES 490.000 0.00 24.944 14.961 14.960 109- 117 TUB HD1 0 YES
490.000 0.00 24.944 14.961 14.960 110- 210 TUB CON 0 YES 490.000
0.00 66.260 19.690 20.450 111- 113 TUB HD1 0 YES 490.000 0.00
24.944 14.961 14.960 117- 111 TUB HD1 0 YES 490.000 0.00 24.944
14.961 14.960 111- 151 TUB VB1 0 YES 490.000 0.00 37.714 19.685
19.680 113- 115 TUB HD1 0 YES 490.000 0.00 24.944 14.961 14.960
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MEMBER PROPERTIES
MEMBER TYPE GRUP FIXITY BUOY DENSITY BETA AREA OD AM-OD
(LB/CUFT) (SQIN) (IN)
115- 155 TUB VB1 0 YES 490.000 0.00 37.714 19.685 19.680 117-
157 TUB VB1 0 YES 490.000 0.00 37.714 19.685 19.680 151- 201 TUB
DB1 0 YES 490.000 0.00 37.714 19.685 21.480 151- 203 TUB DB1 0 YES
490.000 0.00 37.714 19.685 21.480 153- 203 TUB DB1 0 YES 490.000
0.00 37.714 19.685 21.480 153- 205 TUB DB1 0 YES 490.000 0.00
37.714 19.685 21.480 155- 205 TUB DB1 0 YES 490.000 0.00 37.714
19.685 21.480 155- 207 TUB DB1 0 YES 490.000 0.00 37.714 19.685
21.480 157- 201 TUB DB1 0 YES 490.000 0.00 37.714 19.685 21.480
157- 207 TUB DB1 0 YES 490.000 0.00 37.714 19.685 21.480 201- 202
TUB PL2 311000 YES 490.000 0.00 39.936 23.622 1.000 201- 203 TUB
HB2 0 YES 490.000 0.00 24.944 14.961 16.930 207- 201 TUB HB2 0 YES
490.000 0.00 24.944 14.961 16.930 201- 209 TUB HD2 0 YES 490.000
0.00 18.031 14.961 16.930 201- 251 TUB DB2 0 YES 490.000 0.00
24.944 14.961 17.990 201- 257 TUB DB2 0 YES 490.000 0.00 24.944
14.961 17.990 201- 301 TUB LG2 0 NO 490.000 0.00 57.973 29.921
40.000 202- 301 TUB PL2 0 YES 490.000 0.00 39.936 23.622 1.000 203-
204 TUB PL2 311000 YES 490.000 0.00 39.936 23.622 1.000 203- 205
TUB HB2 0 YES 490.000 0.00 24.944 14.961 16.930
203- 209 TUB HD2 0 YES 490.000 0.00 18.031 14.961 16.930 203-
251 TUB DB2 0 YES 490.000 0.00 24.944 14.961 17.990 203- 253 TUB
DB2 0 YES 490.000 0.00 24.944 14.961 17.990 203- 303 TUB LG2 0 NO
490.000 0.00 57.973 29.921 33.320 204- 303 TUB PL2 0 YES 490.000
0.00 39.936 23.622 1.000 205- 206 TUB PL2 311000 YES 490.000 0.00
39.936 23.622 1.000 205- 207 TUB HB2 0 YES 490.000 0.00 24.944
14.961 16.930 205- 209 TUB HD2 0 YES 490.000 0.00 18.031 14.961
16.930 205- 253 TUB DB2 0 YES 490.000 0.00 24.944 14.961 17.990
205- 255 TUB DB2 0 YES 490.000 0.00 24.944 14.961 17.990
205- 305 TUB LG2 0 NO 490.000 0.00 57.973 29.921 33.320 206- 305
TUB PL2 0 YES 490.000 0.00 39.936 23.622 1.000 207- 208 TUB PL2
311000 YES 490.000 0.00 39.936 23.622 1.000 207- 209 TUB HD2 0 YES
490.000 0.00 18.031 14.961 16.930 207- 255 TUB DB2 0 YES 490.000
0.00 24.944 14.961 17.990 207- 257 TUB DB2 0 YES 490.000 0.00
24.944 14.961 17.990 207- 307 TUB LG2 0 NO 490.000 0.00 57.973
29.921 33.320
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DYNPAC SAMPLE PROBLEM DATE 19-JAN-1993 TIME 08:06:21 DYN PAGE
4
MEMBER GROUP SUMMARY WEIGHT REPORT
******** CONSTRUCTION MATERIAL ******** ENTRAPPED *** FLUID
ADDED MASS *** GRUP WEIGHT *** CENTER OF GRAVITY *** FLUID NORMAL
AXIAL X Y Z WEIGHT WEIGHT WEIGHT (KIPS) (FT) (FT) (FT) (KIPS)
(KIPS) (KIPS)
PL4 7.02 0.00 0.00 -85.06 0.00 8.98 0.00 CON 24.75 0.00 0.00
-34.54 0.00 14.59 0.00 HB1 20.21 0.00 0.00 -82.02 0.00 21.36 0.00
DB1 56.29 0.00 0.00 -60.70 0.00 64.28 0.00 LG1 41.47 0.00 0.00
-60.70 48.88 57.10 0.00 PL1 23.54 0.00 0.00 -60.70 0.00 0.06 0.00
HD1 16.14 0.00 0.00 -82.02 0.00 14.90 0.00 VB1 12.76 0.00 0.00
-69.69 0.00 13.48 0.00 PL2 20.19 0.00 0.00 -21.57 0.00 0.05 0.00
HB2 9.75 0.00 0.00 -39.37 0.00 11.52 0.00 HD2 4.98 0.00 0.00 -39.37
0.00 8.15 0.00 DB2 29.66 0.00 0.00 -21.33 0.00 41.27 0.00 LG2 28.92
0.00 0.00 -21.33 42.17 63.27 0.00 HB3 3.79 0.00 0.00 -3.28 0.00
6.84 0.00 HD3 2.68 0.00 0.00 -3.28 0.00 4.84 0.00 PL3 15.89 0.00
0.00 8.20 3.82 5.04 0.00 DK1 99.35 0.00 0.00 21.18 0.00 0.00 0.00
DK2 21.88 0.00 0.00 21.68 0.00 0.00 0.00
MEMBER WEIGHTS X 814.768 KIPS MEMBER CG LOC X -0.101 FT Y
814.768 KIPS Y -0.101 FT Z 644.355 KIPS Z -33.920 FT
WEIGHT OF CONSTRUCTION MATERIAL ........... 439.27 KIPS WEIGHT
OF ENTRAPPED FLUID ................ 94.86 KIPS WEIGHT OF VIRTUAL
MASS (NORMAL) .......... 335.75 KIPS WEIGHT OF VIRTUAL MASS (AXIAL)
........... 0.00 KIPS
SACS WEIGHTS X 373.783 KIPS SACS CG LOCATION X 1.342 FT Y
373.783 KIPS Y 1.341 FT Z 373.783 KIPS Z 19.685 FT
TOTAL WEIGHTS X 1468.887 KIPS TOTAL CG LOC X 0.285 FT Y 1468.887
KIPS Y 0.285 FT
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DYNPAC SAMPLE PROBLEM DATE 19-JAN-1993 TIME 08:06:21 DYN PAGE 5
SACS IV-FREQUENCIES AND GENERALIZED MASS NORMALIZED DEGREES OF
FREEDOM
MODE FREQ.(CPS) GEN. MASS EIGENVALUE PERIOD(SECS) JOINT DOF
1 0.786448 1.5161639E+03 4.0954395E-02 1.2715403 467 DIS Y 2
0.948796 4.3537926E+03 2.8138093E-02 1.0539675 464 DIS X 3 0.950534
3.2428933E+03 2.8035291E-02 1.0520404 461 DIS Y 4 2.650600
5.9550148E+02 3.6053859E-03 0.3772730 467 DIS Z 5 2.681863
1.3067587E+03 3.5218186E-03 0.3728751 464 DIS Z 6 2.945156
2.3794883E+02 2.9202741E-03 0.3395406 467 DIS Z 7 3.257900
1.9377288E+03 2.3865185E-03 0.3069462 105 DIS X 8 3.582488
2.0453946E+02 1.9736532E-03 0.2791356 461 DIS Z 9 3.720677
2.0636038E+02 1.8297694E-03 0.2687683 464 DIS Z 10 4.165966
3.2289680E+02 1.4595155E-03 0.2400403 461 DIS Z
*** M O D A L R E A C T I O N S U M M A R Y ***
MODE X Y Z (KIPS) (KIPS) (KIPS)
1 3.24 -3.24 0.00 2 -85.42 -81.72 0.56 3 70.49 -73.70 0.01 4
-108.04 -108.23 -15.78 5 -169.83 169.50 -0.02 6 18.80 18.89 -19.70
7 -4.02 4.02 0.00 8 -36.23 -36.27 55.90 9 33.91 -33.90 -0.17 10
-5.88 -5.86 -518.96
*** M O D A L S P R I N G S U M M A R Y ***
MODE X Y Z (KIPS) (KIPS) (KIPS)
1 -0.29 0.29 0.00 2 7.87 7.52 -0.05 3 -6.50 6.80 0.00 4 20.78
20.82 1.12 5 32.40 -32.34 0.00 6 -3.32 -3.34 1.41 7 0.87 -0.87 0.00
8 4.85 4.85 -4.50 9 -4.16 4.16 0.01 10 0.48 0.47 45.19
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6.2 SAMPLE PROBLEM 2
The following example illustrates the ability to use an
equivalent foundation super-element and to convert loading in any
load case to mass, therefore eliminating the needto modify the
model for dynamic analysis purposes. Only the degrees of freedom to
beretained for determining the generalized masses and the eigen
vectors were specified inthe model by inputting a 2 in the
appropriate joint fixity column.
Note: Because retaining DOFs has no effect on the model for
staticanalysis, the same model file can be used for static and
dynamicanalyses.
The following is a portion of the model file to be sent through
Seastate for hydrodynamicmodeling. The differences between the
model requirements for sample 1 and this sampleare discussed
below:
A. Unlike Sample Problem 1, pile stub members 2-102, 4-104,
6-106 and 8-108 arenot included in the model. An equivalent
foundation super-element is to be usedas specified on the OPTIONS
line. Therefore, pile stub section PILSTUB andpile stub group PST
are not required in the model input file.
B. The retained degrees of freedom are specified by 2 in columns
55-60 on theappropriate JOINT lines.
C. The pile joints at the mudline are designated with PILEHD
fixity.
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
DYNAMIC CHARACTERISTICS OPTIONS I EN DY SDUC 1 1 1 0 PT
PTSECTSECT CONDSM TUB 66.26 3032.45 1516.22 1516.22 19.690.551
******************* SACS GROUP and MEMBER Lines
*******************************
JOINTJOINT 102 -19.685-19.685-82.021 PILEHDJOINT 104
19.685-19.685-82.021 PILEHDJOINT 106 19.685 19.685-82.021
PILEHDJOINT 108 -19.685 19.685-82.021 PILEHD*******************
More jonts *****************JOINT 257 -11.678 0.000-17.961 JOINT
301 -9.842 -9.842 -3.281 222 JOINT 303 9.842 -9.842 -3.281 222
JOINT 305 9.842 9.842 -3.281 222 LOADCNMISCLOAD Z 405 466
2.65750-3.8892 GLOB CONC SKID1 LOAD Z 405 466 17.6575-4.0025 GLOB
CONC SKID1 LOAD Z 466 468 24.0806-4.2753 GLOB CONC SKID1 LOAD Z 466
468 2.86744-4.0485 GLOB CONC SKID1 LOAD Z 467 468 17.0276-4.3356
GLOB CONC SKID1 LOAD Z 467 468 2.02758-4.4489 GLOB CONC SKID1 LOAD
Z 401 403 -1.969 -1.969 GLOB UNIF WALK1LOAD Z 472 401 -1.969 -1.969
GLOB UNIF WALK1 LOAD Z 403 465 -1.969 -1.969 GLOB UNIF WALK1 LOAD Z
407 405 -1.969 -1.969 GLOB UNIF WALK1 LOAD Z 405 466 -1.969 -1.969
GLOB UNIF WALK1 LOAD Z 471 407 -1.969 -1.969 GLOB UNIF WALK1
END
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As in Sample Problem 1, Seastate and Dynpac were executed in
succession to determinethe dynamic characteristics of the
structure. The output structural data file created bySeastate
containing the effective member properties was used as the SACS
input file forDynpac.
The following is the Dynpac input file followed by a detailed
explanation of the featuresimplemented:
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
TITLE DYNPAC SAMPLE PROBLEM 2
A DYNOPT +ZEN 10CONS 490. 64.2 -80.2 80.2 NF SA-ZB GROVR PL1 N
1.0
GROVR PL2 N 1.0C MBOVR F 301 401 40.0
MBOVR F 201 301 40.0
A. The DYNOPT line specifies the following:a. The vertical
coordinate is the +Z direction and English units are to be used
as specified in columns 8-9 and 10-11 respectively.b. 10 modes
are desired (columns 12-14).c. The consistent mass approach is
specified by CONS in columns 15-18.d. The structure and fluid
density are 490.0 and 64.2 lb/ft3 respectively.e. The mudline
elevation (-80.2) and the water depth (80.2) are specified in
columns 33-39 and 40-46 respectively.f. All members without
flood condition designated, are to be considered non-
flooded for the Dynpac analysis as specified by NF (columns
47-48).g. Loads from the SACS data are to be used as masses and the
Z direction
masses will be opposite sign of the specified Z direction load
(SA-Z incolumns 63-66).
B. The GROVR lines specify that groups PL1 and PL2 (the piles
inside the legs)be non-flooded and have an effective outside
diameter of 1 inch for fluid addedmass and entrapped water mass
calculation.
C. The MBOVR lines specify that members 301-401 and 201-301 have
an effectiveoutside diameter of 40.0 inches for fluid added mass
calculation.
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Figure 1
6.3 SAMPLE PROBLEM 3
The following example illustrates the use of the Dynpac program
to determine thedynamic characteristics of a deck structure.
The deck of a structure modeled to the top of jacket elevation
contains a piece ofreciprocating machinery. The weight of the
machinery along with the weight of othernon-modeled equipment was
specified in Load Case 1. The member mass and massescalculated from
Load Case one will be applied as lumped masses. Figure 2 is a plot
ofthe deck for this sample.
The following are the steps required to execute the Dynpac
analysis:
Miscellaneous loads to account for unmodeled members and
equipment were will beconverted to mass. The degrees of freedom to
be retained for determining the generalizedmasses and the
eigenvectors were designated (using Precede) by specifying a 2 for
thejoint DOF.
The following is the SACS input file used for the analysis:
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812345678901234567890123456789012345678901234567890123456789012345678901234567890
DYNPAC SAMPLE PROBLEM OPTIONS EN DY SDUC 1 1 1 0 PT PTLCSEL DY 1
2 SECTSECT CONDSM TUB 66.26 3032.45 1516.22 1516.22 19.690.551
GRUPGRUP CON CONDSM K 29.0111.6035.97 1 1.001.00 0.50 GRUP DK1
W36X210 29.0111.6035.97 1 1.001.00 0.50 GRUP DK2 W24X131
29.0111.6035.97 1 1.001.00 0.50 GRUP DUM 18.000 2.500
29.0011.6036.00 1 1.001.00 0.50 0.010 GRUP EQ1 24.000 1.500
29.0011.6036.00 1 1.001.00 0.50 0.010 GRUP HB3 11.811 0.394
29.0111.6035.97 1 .800.800 0.50 MEMBERMEMBER0 301 309 HD3 MEMBER0
301 401 PL3
********************* SACS MEMBER AND PLATE MODEL DATA
*************************
JOINTJOINT 1 0.000 0.000-13.281 111001 JOINT 301 -9.842 -9.842
-3.281 111 JOINT 303 9.842 -9.842 -3.281 111 JOINT 305 9.842 9.842
-3.281 111 JOINT 307 -9.842 9.842 -3.281 111 JOINT 309 0.000 0.000
-3.281 JOINT 310 0.000 0.000 -3.281 JOINT 401 -9.842 -9.842 19.685
222 JOINT 403 9.842 -9.842 19.685 222 JOINT 405 9.842 9.842 19.685
222 JOINT 407 -9.842 9.842 19.685 222 JOINT 409 0.000 0.000 19.685
JOINT 461 -29.528-29.528 19.685 222 JOINT 510 -19.685 3.281 28.185
222 LOADLOADCN 1LOAD Z 401 403 -1.969 -1.969 GLOB UNIF 100PSF LOAD
Z 472 501 -1.969 -1.969 GLOB UNIF 100PSF LOAD Z 403 465 -1.969
-1.969 GLOB UNIF 100PSF LOAD Z 407 405 -1.969 -1.969 GLOB UNIF
100PSF LOAD Z 405 466 -1.969 -1.969 GLOB UNIF 100PSF LOAD Z 471 503
-1.969 -1.969 GLOB UNIF 100PSF LOAD Z 461 462 -0.984 -0.984 GLOB
UNIF 100PSF LOAD Z 462 463 -0.984 -0.984 GLOB UNIF 100PSF LOAD Z
463 464 -0.984 -0.984 GLOB UNIF 100PSF LOAD Z 468 467 -0.984 -0.984
GLOB UNIF 100PSF LOAD Z 469 468 -0.984 -0.984 GLOB UNIF 100PSF LOAD
Z 470 469 -0.984 -0.984 GLOB UNIF 100PSF LOAD Z 501 502 -1.969
-1.969 GLOB UNIF 100PSF LOAD Z 502 401 -1.969 -1.969 GLOB UNIF
100PSF LOAD Z 503 504 -1.969 -1.969 GLOB UNIF 100PSF LOAD Z 504 407
-1.969 -1.969 GLOB UNIF 100PSF LOAD Z 472 501 0.984 0.984 GLOB UNIF
100PSF LOAD Z 471 503 0.984 0.984 GLOB UNIF 100PSF LOAD Z 501 502
0.984 0.984 GLOB UNIF 100PSF LOAD Z 502 401 0.984 0.984 GLOB UNIF
100PSF LOAD Z 503 504 0.984 0.984 GLOB UNIF 100PSF LOAD Z 504 407
0.984 0.984 GLOB UNIF 100PSF LOADCN 2LOAD 509 -15.000 GLOB JOIN
MACHINE LOAD 510 -15.000 GLOB JOIN MACHINE END
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The following is a description of the SACS input file:
A. The analysis option specified in columns 19-20 on the OPTIONS
line is DY.
B. The loads of load cases 1 and 2 account for the weight of
unmodeled membersand equipment and will be converted to masses by
Dynpac. The weight of thereciprocating machinery for example, was
modeled as joint loads at joints 509and 510.
C. Joints 1, 301, 303, 305 and 307 are pinned in the global X, Y
and Z directions(joint fixity 111000), the conductor bottom joint 1
is also restrained againstglobal Z rotation.
D. The retained degrees of freedom are specified by 2 in columns
55-60 on theappropriate JOINT lines. For example, Joint 401 is
retained for translation in theX, Y, and Z directions as designated
by 222 in columns 55-57.
The Dynpac analysis was executed specifying the SACS input file
and the followingDynpac input file:
1 2 3 4 5 6 7
812345678901234567890123456789012345678901234567890123456789012345678901234567890
TITLE DYNPAC SAMPLE PROBLEM
A DYNOPT +ZEN 20LUMP 490. -80.2 NF1.0 SA-ZB PLOVR A100A101
400.0C JTWGT 464 15.0 15.0 15.0
JTWGT 465 10.0 10.0 10.0JTWGT 466 10.0 10.0 10.0JTWGT 467 15.0
15.0 15.0END
A. The DYNOPT line specifies the following:a. The vertical
coordinate is the +Z direction and English units are to be used
as specified in columns 8-9 and 10-11 respectively.b. 20 modes
are desired (columns 12-14).c. The lumped mass approach is
speci