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
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
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 .
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
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
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
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
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
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