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TR.28.2 Floor Diaphragm

This command is used to create rigid floor diaphragms without the need to specify a control joint at each. When specified, this command directs the engine to perform the following:

  1. Calculate the center of mass for each rigid diaphragm (where control joint is to be located) considering the mass model of the structure. The mass must be modeled using mass reference load. See TR.31.6 Defining Reference Load Types
  2. Create, internally, an analytical node at the center of mass location to be included during analysis (unless a control node is specified) if an existing analytical node exists at this point, then the existing joint is used in lieu of creating a new joint.
    Tip: The center of mass of each diaphragm is included in the preprocessing output. To include the center of rigidity in the post-processing output, you must include the PRINT DIAPHRAGM CR command. See TR.42 Print Specifications
  3. Search all nodes available within a diaphragm and add them as dependent nodes; with the control node located at the center of mass for the diaphragm (or at the specified control node)

General Format

FLOOR DIAPHRAGM
DIAPHRAGM i1 TYPE RIGID diaphragm-spec
( BASE b1 )

After all diaphragms are defined, the following optional commands can be added:

( CHECK SOFSTORY soft-story-code )
( CHECK IRREGULARITIES CODE irregularities-code )

where:

diaphragm-spec = HEIGHT f1 ( CONTROL i2 ) (JOINT joint-list ) 

or

diaphragm-spec = YRANGE f2 f3 ( CONTROL i2 ) ( JOINT XRANGE f4 f5 ZRANGE f6 f7 )

or

diaphragm-spec = ( CONTROL i2 ) JOINT joint-list
ParameterDescription
DIAPHRAGM i1 Diaphragm identification number
BASE b1 base/ground floor level of the structure when not at the minimum Y coordinate defined in the model
HEIGHT f1 Global coordinate value, in Y direction, to specify the floor level
YRANGE f2 f3 Global coordinate values to specify a Y range, where f2 is the lower bound and f3 is the upper bound. The diaphragm is considered to be located at that floor height.
XRANGE f4 f5 Global coordinate values to specify an X range. The diaphragm is considered to be located between this X range. If full floor is to be considered as only one diaphragm there is no need to define X range.
ZRANGE f6 f7 Global coordinate values to specify Z range. The diaphragm is considered to be located between this Z range. If full floor is to be considered as only one diaphragm there is no need to define Z range.
CONTROL i2 User-specified control joint number at the specified floor level. If not defined, the program will automatically calculate this joint as the diaphragm center of mass.

Instead of providing height or Y-range, joint lists can be provided to indicate the number of joints present at a particular floor level which will be connected to a control joint (either specified or calculated by the program).

Soft Story and Irregularities Checks

Refer to TR.28.2.1 Soft Story Checking for details on soft-story-code and to TR.28.2.2 Check Irregularities for details on irregularities-code.

Notes

  1. One full diaphragm definition should be provided per line. However, if there is joint-list, the list can extend to the second line with a continuation sign ("-").

    DIA f1 TYP RIG YR f2 f3 JOI XR f4 f5 ZR f6 f7
    DIA f11 TYP RIG YR f21 f31 JOI XR f41 f51 ZR f61 f71
    DIA f12 TYP RIG JOI 35 45 51 TO 57 59 TO 83 -
    90 TO 110
    

    where f1, f11, and f12 are three rigid diaphragms located at floor height ranging between f2 and f3, f21 and f31, and the joints lying in the plane as indicated by their global Y coordinates respectively.

  2. Diaphragms should be specified in ascending order (i.e., diaphragms at first floor level should be specified first before specifying that on 2nd floor level and so on).
  3. If a user-defined control joint is specified in one diaphragm, then user-defined control joints should be specified for all diaphragms. Combination of user-defined control joint for one diaphragm and program calculated control joint for another diaphragm is not supported.
  4. The mass model (in terms of reference load) must be specified before specifying floor diaphragm .
  5. Floor diaphragms can be specified only once in an input file.
  6. Floor diaphragm cannot be specified along with the FLOOR HEIGHT command (refer to TR.31.2.9.1 Identification of Floor Level).
  7. Floor diaphragm cannot be specified along with the CONTROL-DEPENDENT command (refer to TR.28.1 Control/Dependent Specification).
  8. Floor diaphragm cannot be specified with the SET Z UP command.
  9. Sloped diaphragms are not supported.
  10. Base level (or ground floor level or support level) is taken as the minimum of Y coordinates defined. Different base level can be specified using the BASE b1 option in the command. If used, this option must be the last line of the floor diaphragm system.
  11. The maximum number of diaphragms allowed by the program (default value) is 150. If more than 150 diaphragms need to be specified, then SET RIGID DIAPHRAGM n must be specified before specifying joint incidence, where n = total number of diaphragms in the structure.

Example

***********************************************************
UNIT FEET KIP
DEFINE REF LOAD
LOAD R1 LOADTYPE MASS
* MASS MODEL
SELFWEIGHT X 1
SELFWEIGHT Y 1
SELFWEIGHT Z 1
JOINT LOAD
17 TO 48 FX 2.5 FY 2.5 FZ 2.5
49 TO 64 FX 1.25 FY 1.25 FZ 1.25
*
LOAD R2
SELFWEIGHT Y -1
JOINT LOAD
17 TO 48 FY -2.5
49 TO 64 FY -1.25
END DEF REF LOAD
****************************************************************
FLOOR DIAPHRAGM
DIAPHRAGM 1 TYPE RIGID YR 4.1 4.3 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 2 TYPE RIGID YR 8.3 8.5 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 3 TYPE RIGID YR 12.5 12.7 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 4 TYPE RIGID YR 16.7 16.9 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 5 TYPE RIGID YR 20.9 21.1 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 6 TYPE RIGID YR 25.1 25.3 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 7 TYPE RIGID YR 29.3 29.5 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 8 TYPE RIGID YR 33.5 33.7 JOI XR -0.1 21.3 ZR -0.1 31.9
DIAPHRAGM 9 TYPE RIGID YR 37.7 37.9 JOI XR -0.1 21.3 ZR -0.1 31.9
BASE 0.5
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