OpenSees dynamic_analysis
4 likes3,057 views
This document describes performing dynamic analysis on a column structure subjected to earthquake loading. The model consists of a column fixed at one end and free at the other. Mass is defined at the free end and a sinusoidal acceleration time history is applied as the input ground motion. The column is discretized into elements and both static and transient dynamic analyses are performed. Results such as displacements, reactions, and member forces are recorded. Assignments involving modifying parameters like mass location, applied loads, and discretization are provided to further study the structural response.
OpenSees dynamic_analysis
- 1. Dynamic Analysis By Dhanaji S. Chavan , Assistant Professor, TKIET, Warananagar
- 2. Problem-1 4 m -6.00E-01 -4.00E-01 -2.00E-01 0.00E+00 2.00E-01 4.00E-01 6.00E-01 0 1 2 3 4 5 acceleration time E= 2.1e8 kPa C/s: 0.3mx0.3m Input motion is given 500 kN
- 3. …………….. • Objectives: to determine……… – Displacement at fee end & fixed end – Reactions at free end & fixed end – Local & global forces in the column – Plot displacement time history at free end for first 2 second
- 4. Coding starts………. model basic -ndm 2 -ndf 3 node 1 0 0 node 2 0 4 fix 1 1 1 1
- 5. To define mass • In dynamic analysis it is must to define nodal or elemental mass – Beacause Transient(earthquake) motion develops inertial force which is f=m .a Inertial force mass Acceleration to which mass is subjected
- 6. …….. mass $nodeTag (ndf $MassValues) Node number at which mass to be defined command Mass for specific degree of motion
- 7. ………… mass 2 50 00 0 command Node number Mass in x- direction Mass in y direction Mass in the direction of rotation
- 8. ………. • while defining mass we have to be very careful. • In present case earthquake motion is in x- direction, so we have to define mass in that direction • If we defined mass in any other direction that will be ineffective in analysis
- 9. …………. geomTransf Linear 1 element elasticBeamColumn 1 1 2 .09 2.1e8 0.000675 1 recorder Node -file Rbase.out -time -node 1 -dof 1 2 reaction recorder Node -file RFree.out -time -node 2 -dof 1 2 reaction recorder Node -file Dbase.out -time -node 1 -dof 1 2 disp recorder Node -file Dfree.out -time -node 2 -dof 1 2 disp recorder Element -file ele_Lfor.out -time -ele 1 localForce recorder Element -file ele_Gfor.out -time -ele 1 globalForce
- 10. ………… pattern Plain 1 Constant { load 2 000 -500.0 0.0} – Remember that self weight of the super structure has to be applied separately as a force. It won’t be calculated automatically form mass .
- 11. ............. system UmfPack constraints Plain test NormDispIncr 1.0e-5 10 0 algorithm Newton numberer RCM integrator LoadControl 1 analysis Static analyze 10
- 12. Quick review of integrator LoadControl integrator LoadControl $dLambda1 <$Jd $minLambda $maxLambda> $dLambda1: - first load-increment factor (pseudo-time step) - Usually same is followed further <$Jd: - must be integer -factor relating load increment at subsequent time steps minLambda, maxLambda: -decides minimum &maximum time increment bound - optional, default: $dLambda1 for both Dhanaji Chavan 12
- 13. ………. loadConst -time 00.00 – This command is used to restart the time for the transient analysis command keyword Start time
- 14. ………. wipeAnalysis – This command clears previously-defined analysis parameters. i.e. parameters defined for static analysis
- 15. To define the input motion.. set accelSeries "Series -dt 0.01 -filePath INPUT_accl.dat -factor 1“ Set: command accelSeries: variable name to which acceleration time history is to be assigned • Portion in the box is a time Time Series
- 16. Time Series • Types of time series are : i. Constant Time Series ii. Linear Time Series iii. Rectangular Time Series iv. Sine Time Series v. Path Time Series • For the first four time series the load variation follows fixed pattern.
- 17. ……….. • When load pattern does not follow a fixed pattern i.e. earthquake load, we have to go for Path Time Series
- 18. Ways to define Path Time Series where the values are specified in a list included in the command & at constant time interval Series -dt $dt -filePath $fileName <-factor $cFactor> – In our case we have used this series keyword File name which contains the values e.g. accl, vel,load etc keyword Constant time interval e.g 0.01 keyword Load factor coefficient. Default value is 1
- 19. …………. The load factor to be applied to the loads in the LoadPattern object is : – load factor = $cFactor*(user-defined series)
- 20. Ways to define Path Time Series For a load path where the values are specified at constant time intervals: Series -dt $dt -values {list_of_values} <-factor $cFactor> keyword Constant time interval e.g 0.01 keyword List of values e.g. accl, vel, load etc keyword Load factor coefficient. Default value is 1
- 21. ………… • For a load path where the values are specified at non- constant time intervals: Series -time {list_of_times} -values {list_of_values} <-factor $cFactor> • where both time and values are specified in a list included in the command: Series -fileTime $fileName1 -filePath $fileName2 <-factor $cFactor>
- 22. To define load pattern pattern UniformExcitation $patternTag $dir -accel (TimeSeriesType arguments) <-vel0 $ver0> • Pattern: command • UniformExcitation: name/type of load pattern • $patternTag: unit pattern tag/ number • $dir: direction of excitation (1, 2, or 3) used in formulating the inertial loads for the transient analysis • -accel: keyword to define acceleration history • -vel0: keyword to define initial velocity $ver0 whose default value is zero
- 23. …………… In our case……. pattern UniformExcitation 2 1 -accel $accelSeries Unique pattern tag Direction of excitation X-direction A uniform acceleration history is imposed at all nodes constrained in the x-direction i.e. in our case node 1 only
- 24. Defining Dynamic analysis commands……………… system ProfileSPD test NormDispIncr 1.e-6 50 0 algorithm KrylovNewton constraints Transformation
- 25. To define integrator • We can not use the integrator defined for static analysis • We have to define the following integrator integrator Newmark $gamma $beta command Name of the integrator Newmark parameter Newmark parameter
- 26. ………… Integrator Newmark 0.5 0.25 numberer RCM analysis Transient analyze 4000 0.01 Thank u……………………………………
- 27. Assignment -1. 1. Perform both static & dynamic analysis for given problem discretizing into one element only 2. Don’t define nodal mass & see what happens 3. Define the mass in y direction & see the results 4. Apply both vertical & lateral static loads at free end & perform the analysis 5. Don’t use the loadConst -time 00.00 & see what happens
- 28. Assignment -2 • Discretize above model in 4 elements & perform the complete analysis
- 29. Problem- 2 1(0,0) 2(1,0) 3(1,1)4(0,1) E= 2.1e8 kPa, mass density = 1.6 ton/m3 input motion: sinusoidal acceleration at base 3.0
- 30. ……… Wipe model basic -ndm 2 -ndf 2 nDMaterial ElasticIsotropic 1 2.1e8 0.3 node 1 0.000 0.000 node 2 1.000 0.000 node 3 1.000 1.000 node 4 0.000 1.000
- 31. ………… element quad 1 1 2 3 4 1.0 "PlaneStrain" 1 0.0 0.0 0 -16 Surface pressure Mass density Body force in x direction Body force in y direction
- 32. ……… fix 1 1 1 fix 2 1 1 system ProfileSPD test NormDispIncr 1.e-12 25 0 constraints Transformation integrator LoadControl 1 1 1 1 algorithm Newton numberer RCM analysis Static
- 33. ……………….. analyze 1 loadConst -time 0.000 wipeAnalysis
- 34. Application of earthquake motion pattern UniformExcitation 1 1 -accel "Sine 0 1000 1 -factor 10" Sinusoidal variation Start time End timePeriod of sine wave Load factor coefficient
- 35. ………………. constraints Transformation; test NormDispIncr 1.e-12 25 0 algorithm Newton numberer RCM system ProfileSPD integrator Newmark 0.5 0.25 analysis Transient recorder Node -file disp.out -time -node 1 2 3 4 -dof 1 2 -dT 0.01 disp recorder Node -file acce.out -time -node 1 2 3 4 -dof 1 2 -dT 0.01 accel recorder Element -ele 1 -time -file stress1.out -dT 0.01 material 1 stress recorder Element -ele 1 -time -file strain1.out -dT 0.01 material 1 strain recorder Element -ele 1 -time -file stress3.out -dT 0.01 material 3 stress recorder Element -ele 1 -time -file strain3.out -dT 0.01 material 3 strain analyze 2000 0.01
- 36. …………… recorder Node -file disp.out -time -node 1 2 3 4 -dof 1 2 -dT 0.01 disp recorder Node -file acce.out -time -node 1 2 3 4 -dof 1 2 -dT 0.01 accel recorder Element -ele 1 -time -file stress1.out -dT 0.01 material 1 stress recorder Element -ele 1 -time -file strain1.out -dT 0.01 material 1 strain recorder Element -ele 1 -time -file stress3.out -dT 0.01 material 3 stress recorder Element -ele 1 -time -file strain3.out -dT 0.01 material 3 strain analyze 2000 0.01
- 37. Assignment-3 1. Perform both static & dynamic analysis for given problem &……… Plot displacement time history plot for node 3 & 4 Plot acceleration time history plot for node 3 & 4
- 38. Assignment-4 • Discretize domain in 4 elements & perform the complete analysis
- 39. Assignment- 5 • Apply equal dof for node 3 & 4 , perform dynamic analysis and Plot displacement time history plot for node 3 & 4 Plot acceleration time history plot for node 3 & 4
- 40. ……… equalDOF 3 4 1 2 Thank u............