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Response Spectrum Data Created Edited

Response Spectrum Functions

Function

  • Enter spectral data for response spectrum analysis.
  • Response Spectrum Analysis calculates modal responses using the natural periods obtained by Eigenvalue analysis. Therefore, Response Spectrum Function must be defined, which includes the range of the considered natural periods obtained from the Eigenvalue analysis.

01-RSF-1.jpg

Range of the natural periods obtained from Eigenvalue analysis

 

Call

From the main menu, selecet [Load] tab > [Type : Dynamic Loads] > [Response Spectrum Data] group > [RS Functions]

 

Input

Load-Dynamic Load-Response Spectrum Data-Response Spectrum Function.png

Add

Enter new or additional spectral data

 

Modify/Show

Modify previously entered spectral data. Select the relevant spectral data from the spectral data list of the dialog box and click the Modify/Show button.

 

Delete

When deleting previously entered spectral data. Select the relevant spectral data from the spectral data list of the dialog box and click the Delete button.

 

Click the Add button or the Modify/Show button to display the dialog box below and enter the required data in the relevant entry fields.

 


Load-Dynamic Load-Response Spectrum Data-Response Spectrum Function-add.png

Add/Modify/Show Response Spectrum Functions dialog box

 

How to enter spectrum data

Create files containing frequently used response spectrum load cases, then retrieve the files

Import File : Use the method to enter previously created spectral data.The data are saved with a '.sgs' or '.spd' extension and written in the following formats :

 

'fn.sgs' file format

*SGSw To define that the file is in "Seismic Data Generator" data format which is a MIDAS/Civil module that auto-extracts seismic data
*TITLE, MAINTITLE

Description for main title

Ex. ATC 3-06 Design Spectrum

*TITLE, SUBTITLE

Description for subtitle

Ex. Soil = 1.0 Aa = 1.00 Av =1.00 RMF = 1.00

*X-AXIS, LEGENDX

Description for horizontal axis

Ex. Period Tn (sec)

*Y-AXIS, LEGENDY

Description for vertical axis

Ex. Absolute Acceleration (g)

*UNIT&TYPE, UNIT, TYPE

Description for units in use and data type

UNIT: GRAV, MM, CM, M, INCH (IN, IN.), FEET (FT, FT.) allowed.

TYPE: ACCEL (Acceleration), VELO (Velocity), DISP (Displacement) allowed

*FLAGS, SPECTYPE, DAMPINGUSE

Description for spectrum type and damping ratio in use

SPECTYPE: 1 for Tripartite spectrum type, 0 for the other cases

DAMPINGUSE: 1 for using Damping Ratio, 0 for not using Damping Ratio

*DATA

To define where the data starts

*DAMPING, DAMPINGRATIO

Description for damping ratio

It is defined when damping ratio is 1 only.

X-Data, Y-Data

X: Period, Y: Spectral Data

X-Data: Spectral Data for X-axis

Y-Data: Spectral Data for Y-axis

Ex. 1.00000E-006, 2.50000+000

      1.20000E-001, 2.50000E+000

*ENDDATA

To define when the data ends

It is used after *DATA is defined.

 

Example of a '*.sgs' file

 

'fn.spd' file format - User-defined

*UNIT

Description for units in use

UNIT: MM, CM, M, INCH, FEET, GRAV allowed

*TYPE

Description for data type

TYPE: ACCEL (Acceleration), VELO (Velocity), DISP (Displacement) allowed.

*DATA To define when the data starts
X-Data, Y-Data

X: Period, Y: Spectral Data

Ex. 1.00000E-006, 2.50000+000

      4.00000E-002, 2.50000E+000

… (Repeat for each data point)

1.20000E-001, 2.50000E+000

 

Example of a '*.spd' file

 

'fn.thd' file format - User-defined ** Comments - Entry allowed anywhere

*UNIT, LENGTH, FORCE

Description for length and force

LENGTH: MM, CM, M, INCH(IN, IN.), FEET(FT, FT.) allowed

FORCE: KG, KGF, TON, N, KN, LBF, KIP, NULL allowed

*TYPE

Description for data type

TYPE: ACCEL (Acceleration), VELO (Velocity), DISP (Displacement) allowed.

*DATA To define when the data starts
X-Data, Y-Data

X: Period, Y: Spectral Data

Ex. 1.00000E-006, 2.50000+000

      4.00000E-002, 2.50000E+000

… (Repeat for each data point)

  1.20000E-001, 2.50000E+000

 

Example of a '*.thd' file

 


Access the built-in response spectrum load cases in midas Civil database

Design Spectrum : Use the feature to enter spectrum functions created in accordance with the standards. Select the standard from the spectrum function list and enter the desired parameters.

 

The built-in design spectrum types are as follows :

IBC2000(ASCE7-98): International Building Code 2000
UBC (1997): UBC 97 standards
UBC 88-94: UBC 91 standards
NBC (1995): National Building Code of Canada 1995
NTC 2018: Italian technical standards
Eurocode-8 (2004): Design provisions for earthquake resistance of structures. General rules. Strengthening and repair of buildings.
Eurocode-8 (1996) Design: Design provisions for earthquake resistance of structures. General rules. Strengthening and repair of buildings.
Eurocode-8 (1996) Elastic: Design provisions for earthquake resistance of structures. General rules. Strengthening and repair of buildings.
Romania (P100-1,2013): Seismic Design Code.
AS 5100.2: 2017: Australian highway bridge design standard
DPWH-BSDS 2013: Philippines highway bridge design standard
IRC SP 114:2018: Seismic Design of Road Bridges

NOTE.png Seismic zone factor, Importance factor and Response Reduction Factor can be specified as user input.

IS1893 (2002): Indian Standards
TaiwanBrg (89) Horizontal: Taiwan Seismic Code
TaiwanBrg (89) Vertical: Taiwan Seismic Code
China (GS50011-2001): For Chinese version

NOTE.png Specific period (Tg) can be modified by the user.

China (JTJ004-89): For Chinese version

NOTE.png Specific period (Tg) and horizontal seismic coefficient (ku) can be modified by the user.

China (GBJ111-87): For Chinese version

NOTE.png Specific period (Tg) and horizontal seismic coefficient (ku) can be modified by the user.

China Shanghai (DGJ08-9-2003): Shanghai Code for Seismic Design of Buildings
Japan (Arch, 2000): For Japanese version
Japan (Bridge2002)
Korea (Bridge): Specification for Roadway Bridge
Korea (Arch, 2000): Buildings loading criteria and commentaries
Korea (Arch, 1992): Regulations related to structural criteria for buildings

NOTE.png Importance factor (I) in the combo box can be defined by selecting the factor in the drop-down menu or by typing the factor directly.

 

Load-Dynamic Load-Response Spectrum Data-Response Spectrum Function-generate design spectrum.png

Generate Design Spectrum dialog box

 


Enter directly the spectral data in the entry fields in the Add/Modify/Show Response Spectrum Functions dialog box

The user directly enters the period and spectrum values in the entry field to the left of the dialog box.

For easy interpretation, the spectrum functions are processed in graphs representing spectrum values vs periods. The spectrum functions corresponding to the natural periods of the structure are linearly interpolated in the response spectrum analysis. Thus, it may be prudent to provide functional values at closed intervals where the curvature suddenly varies. In addition, the range of periods for the spectrum functions must include all the natural periods of the structure.

 


Function Name

Enter the name of the spectral data. The name is used in "Response Spectrum Load Cases" which is the function used to enter response spectrum load cases.

 


Spectral Data Type

Assign the spectral data type to be entered.

Normalized Accel. : Spectrum obtained by dividing the acceleration spectrum by the acceleration of gravity

 

Acceleration : Acceleration spectrum

 

Velocity : Velocity spectrum

 

Displacement : Displacement spectrum

NOTE.png If the type of entered response spectral data is changed, the data are not converted according to the unit of the data type.  Rather only the application type of the entered data is changed.

 


Scaling

Scale Factor : Specify a multiplier for Response Spectrum Data. When changing the Spectral Data Type with spectrum data already entered, the data entered will not automatically change according to the new unit. Only the display format will be updated. Therefore, by entering the increment/decrement amount due to the unit conversion as a Scale Factor, you can reduce the inconvenience of having to manually change all the spectrum data.

 

Maximum Value : Maximum value of Response Spectrum Data can be controlled by the user. For example, if the maximum value of the entered acceleration is 10g, and you enter 2g as the Maximum Value, the maximum value of the spectrum will be scaled down to 2g.

 


Gravity

Enter the acceleration of gravity.

 


Damping Ratio

Specify a Damping Ratio applicable to the response spectrum, which will be used in response spectrum analysis.

If the damping ratio applied in the development of the response spectrum differs from the damping ratio of the structure for which the analysis is performed (Apply Damping Method in Response Spectrum Load Cases), the spectrum data is processed and applied according to the damping ratio of the structure. There are several methods for processing spectrum data, including interpolation using multiple spectrum data and correction equations.

 


Graph Options

Specify whether or not to produce a graph in Log Scale.

 


Description

Enter a brief description of Response Spectrum Data. When the Design Spectrum has been generated, the basic Spectrum Data such as soil & area coefficients and importance & response factors are displayed.

For convenience, midas Civil supports the following 4 entry methods:

1. Create files containing frequently used response spectrum load cases, which are then retrieved for later uses
2. Access the built-in response spectrum load cases in the database
3. Use Seismic Data Generator to enter the load cases
4.The user directly enters the load cases

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