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GT STRUDL Transient Loading Commands

V 3 2.4.4 - 1 Rev P

2.4.4.4 Transient Loading Commands

The transient loading commands are used to describe a transient load on the structure.

The resulting dynamic analysis is either performed using mode superposition analysis or a

direct integration (physical) analysis.

2.4.4.4.1 Transient Loading Identification Command

General Form:

TRANSIENT (LOADING)i

a(title)

Elements:

i = unique integer loading condition identifier

a = unique alphanumeric loading condition identifier (up to 8 characters)

title = optional loading condition title (up to 64 characters)

Explanation:

This command identifies a transient loading condition and initiates its

description. The commands used to specify the transient loading condition are

contained in the following section.

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Transient Loading Commands GT STRUDL

Rev P 2.4.4 - 2 V 3

load specs

FILE filnam ([ FACTOR] v1)

function specs

FUNCTIONSINE

COSINE[AMPLITUDE] v

2[FREQUENCY] v

3( [PHASE] v

4)

2.4.4.4.2 Transient Joint Loads

General Form:

JOINTS

NODESlist (LOADS)

FORCE

MOMENT

X

Y

Z

load specs

where,

function specs =

and where,

filnam = previously stored time history (Section 2.4.4.1)

v1 = factor to be multiplied times ordinates of the forcing function

(if omitted, a value of 1.0 is used)

v2 = amplitude of sine/cosine function loading in active units

v3 = frequency of sine/cosine function loading in active units

v4 = phase of sine/cosine function loading in active units

(default = 0.0)

Explanation:

This command is used to specify a time history of loads applied to a list of

joints in the global X, Y, or Z directions. The loads may be specified in either of two

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V 3 2.4.4 - 3 Rev P

v2

sin

cos(v

3t v

4)

ways:

(1) by reference to a previously stored time history (Section 2.4.4.1), or

(2) specification of a trigonometric (sine/cosine) function.

A previously stored time history (Section 2.4.4.1) of type FORCE

TRANSLATION or FORCE ROTATION may be applied as a JOINT LOAD with

the FILE option. If the stored time history does not match the type specified in this

command (FORCE or MOMENT) an error message will be printed and SCAN mode

will be entered.

For trigonometric loadings, the time history may be given by specifying the

function (SINE or COSINE), amplitude, frequency, and phase angle. Thetrigonometric loading used is given by the following expression, where t represents

time:

Examples:

(1) Joints 1 TO 3, 5, A LOADS FORCE Y FILE WIND-1' FACTOR 1.5. This

command specifies that the previously stored time history WIND-1' should

have its ordinates multiplied by 1.5 and applied as a force in the Y-direction

at the listed joints.

(2) JOINT 1,2 LOAD MOMENT Z FUNCTION SINE AMPL 5.0 FREQ 1.0.

A sinusoidal moment Z load with amplitude of 5.0 and frequency of 1. in

current units is applied at joints 1 and 2.

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Rev P 2.4.4 - 4 V 3

TRANSLATION

X

Y

Zload specs

2.4.4.4.3 Support Acceleration Command for Transient Loading

General form:

SUPPORT (ACCELERATION)

`

`

`

TRANSLATION

X

Y

Z

load specs

where,

load specs = same as for JOINT LOAD Command (Section 2.4.4.4.2)

Explanation:

This command is used to specify time history support acceleration loads. The

accelerations may only be of type TRANSLATION in the global X, Y, or Zdirections. Up to three support accelerations (X and/or Y and/or Z) may be specified

in a single TRANSIENT LOADING.

All support joints are assumed to have the identical support accelerations. All

support joints are assumed to move as one rigid body with no relative motion.

The load specs are identical to the load specs for the JOINT LOAD command

in Section 2.4.4.4.2, except that the loads are translational accelerations instead of

forces and moments. If the FILE option is used, the previously stored time history

must have been of the type ACCELERATION presented in Section 2.4.4.1, or must

have been created and stored with the CREATE TIME HISTORY command as

described in Section 2.4.8.1. Otherwise, an error message will be printed, and the

SCAN mode will be entered. Displacement and velocity results are computed

relative to the supports. The accelerations may be computed relative to the supports.

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V 3 2.4.4 - 5 Rev P

The accelerations may be computed relative to the supports or absolutely as described

in Section 2.4.5.3.

Examples:

(1) SUPPORT ACCELERATION

TRANSLATION X FILE ELCENTRO

This command specifies the use of the N-S component of the El Centro earthquake

(provided with GTSTRUDL) as an applied support acceleration in the global X

direction of the structure.

(2) SUPPORT ACCELERATION

TRANSLATION Y FILE QUAKE-TX FACTOR 0.2

This command specifies a translational support acceleration in the global Y-direction

where acceleration values previously stored in file QUAKE-TX times the factor 0.2

are used as the applied support acceleration.

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Rev P 2.4.4 - 6 V 3

2.4.4.4.4 Transient Loading for Matrix Input

General form:

ROWi1

i2

TO i3

(LOAD) load specs

where,

load specs = same as for JOINT LOAD command (Section 2.4.4.4.2)

Elements:

i1 = integer ROW or equation number to which the loading is applied

i2, i3 = starting and ending ROW or equation numbers to which the loading

is applied (i3> i2).

Explanation:

This command is used to specify time history loads to structures whose

matrices have been directly input using the MATRIX command described in Section2.4.3.4. The load specification description presented with the JOINT LOAD

command of Section 2.4.4.4.2 also applies here, except that no check is made on the

type of time history referenced when using the FILE option. It is the users

responsibility to ensure that the use of a previously stored time history (Sections

2.4.4.1 and 2.4.8.1) is meaningful. Note that the ROW identifiers must consist of

either a single row identifier or a contiguous group of row identifiers.

Examples:

(1) ROW 1 LOAD FILE BLAST

ROW 3 TO 5 LOAD FILE BLAST

The time history stored under the name BLAST is applied to rows 1, 3, 4, 5.

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V 3 2.4.4 - 17 Rev P

condition specs

DISPLACEMENT values

VELOCITY values

2.4.4.4.5 Initial Conditions Commands

(1) General form except for Matrix Input:

INITIAL (CONDITIONS) (condition specs)

list (condition specs)

`

`

`

list (condition specs)

Elements:

values = [XT] v1[YT] v2[ZT] v3[XR] v4[YR] v5[ZR] v6

list = list of joint identifiers

v1,v2,v3 = X, Y, Z initial joint translation displacements or velocities

v4,v5,v6 = X, Y, Z initial joint rotation displacements or velocities.

(2) General form for Matrix Input:

INITIAL (CONDITIONS) ROW (condition specs)

rowlist (condition specs)

`

`

`

rowlist (condition specs)

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Rev P 2.4.4 - 18 V 3

where,

rowlist

i1

i2 TO i3

condition specs

DISPLACEMENT v1

VELOCITY v2

Elements:

i1 = row identifier corresponding to Matrix Input row

i2,i3 = initial and final row identifiers

v1,v2 = initial displacement and velocity for row i1or rows i2to i3

Explanation:

This command allows the user to specify the initial conditions (DISPLACE-

MENTS and/or VELOCITIES) for (1) the joint degrees-of-freedom in the general

case of structure input, or (2) the equations of motion when the system matrices have

been input via the MATRIX command (Section 2.4.3.4).

The following qualifications relate to the specifications of initial conditions

at local released support joints, master joints, and slave joints:

1. At local release support joints, initial conditions components are

defined with respect to the local released coordinate system as shown

in Figure 2.1.7.1, Section 2.1.7.2, Volume 1 of the GTSTRUDL

Users Manual.

2, At master nodes, initial conditions components are defined with

respect to the planar coordinate system of the planar rigid body (rigid

plane, plate or pin elements) which is connected to the master node.

If the master node is also a local released support joint, then qualifica-

tion (1) above also applies.

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3. Initial conditions specified for slave degrees-of-freedom are ignored.

However, initial conditions may be given for slave released degrees-

of-freedom specified by the SLAVE RELEASES command (Section

2.6.4.3). If slave releases are specified with respect to a local slavereleased coordinate system, then corresponding initial conditions

components are defined with respect to that coordinate system,

similar to (1) above for local released support joints.

The command has a tabular format so that the condition specifications on the

command header will act as default values for the joints or rows listed in the table.

Values v1to v6listed following a list or a rowlist will override their corresponding

condition spec types given in the command header,

Examples:

(1) INITIAL CONDITIONS DISP YT 1.0 VEL XR 1.51 TO 5 DISP XT 2.0 YT 05

6 TO 10 DISP XT 3.0

The following data are stored:

Joints 1 to 5: Displacement XT = 2.0Displacement YT = 0.5

Velocity XR = 1.5

Joints 6 to 10: Displacement XT = 3.0Displacement YT = 1.0Velocity XR = 1.5

(2) INITIAL CONDITIONS ROW DISP 1.0

1 DISP .5 VEL 1.0

3 TO 5 VEL 2.0

The following data are stored:

row 1: Displacement = 0.5

Velocity = 1.0rows 3,4,5: Displacement = 1.0

Velocity = 2.0

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Rev P 2.4.4 - 20 V 3

2.4.4.4.6 Specification of Integration Time Parameters

General form:

INTEGRATE [FROM] t1l [TO] t12 [AT] t13[FROM] t21 [TO] t22 [AT] t23 `

`

`

[FROM] tn1 [TO] tn2 [AT] tn3

Elements:

t11, t21,...,tn1 = initial time valuest12, t22,...,tn2 = final time values

t13, t23,...,tn3 = values of time increments to be used in the integration

Explanation::

This command specifies the initial and final times and time increment for

transient loadings. A variable time increment may be specified by a sequence of

initial and final times with the associated time increment~. The initial time of one

sequence must be greater than or equal to the final time of the previous sequence.The time increment must be positive. This command must be given for all transient

loadings.

Examples:

(1) INTEGRATE FROM 0.0 TO 0.5 AT 0.1

In the above example, the transient response is calculated at

0.0, 0.1, 0.2, 0.3, 0.4, 0.5

(2) INTEGRATE FROM 0.0 TO 0.3 AT 0.1FROM 0.3 TO 0.5 AT 0.05

FROM 0.6 TO 0.8 AT 0.1

In the above example the time history response is calculated at 0.0, 0.1, 0.2,

0.3, 0.35, 0.40, 0.45, 0.5, 0.6, 0.7, and O.8.

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2.4.4.4.7 Termination of a Transient Loading

General form:

END (OF TRANSIENT LOADING)

Explanation:

A TRANSIENT LOADING condition description is terminated by issuing

this command. Several complete transient loading conditions are provided as

follows:

Examples:

(1) TRANSIENT LOADING 'EQI' 'VERTICAL (Y) AND HORIZONTAL (X AND Y)'

SUPPORT ACCELERATION

TRANS X FILE 'ELCENTRO'

TRANS Y FILE 'ELCENTRO' FACTOR .5

TRANS Z FILE 'ELCENTRO'

INTEGRATE FROM 0. TO 6. AT .02

END OF TRANSIENT LOADING

The El Centro support acceleration is applied to the structure in 3 directions, two

lateral and one vertical. The vertical motion is factored by one-half. Since El Centro

is stored at .02 second intervals and a time increment of .02 is used, no accelerogrampeaks will be missed.

(2) UNITS CYCLES POUNDS IN SECONDS

$

$ OUT-OF-BALANCE MOTOR FORCE = MASS * ECCENT * FREQ**2

$ = .1 * 7. * (50*2PI)**2

$ = .1 * 7. * 98696.

$ = 69087.

TRANSIENT LOAD 1 'SHAKE'

UNITS CYCLES

JOI 'A ' LOAD FOR X FUNCT COS AMPL 69087. FREQ 50. PHASE 0.

JOI IA ' LOAD FOR Y FUNCT COS AMPL 69087. FREQ 50. PHASE -.25

INTEGRATE FROM 0. TO . 2 AT . 002

END OF TRANSIENT LOAD

This example illustrates how a transient loading would be set up to handle the case

of an out-of-balance motor.

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