Block Format Keyword Defines a preloading stress applied to the section of a 3D bolt.


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
sect_ID sens_ID Itype   Preload Tstart Tstop


Field Contents SI Unit Example
preload_ID Bolt preloading block identifier.

(Integer, maximum 10 digits)

unit_ID Optional unit identifier.

(Integer, maximum 10 digits)

preload_title Bolt preloading block title.

(Character, maximum 100 characters)

sect_ID Section identifier to which the preloading is applied. The preloading force is applied along local Z direction of the section. 2


sens_ID Sensor identifier.
Preloading stress is applied after sensor activation. Tstart and Tstop are shifted in time accordingly.


Itype Preloading type.
= 1 (Default)
Preload is a force.
= 2
Preload is a stress.


Preload Preloading value.

Default = 0.0 (Real)

[ N ] or [ Pa ]
Tstart Start time for bolt preloading. 6

Default = 0.0 (Real)

[ s ]
Tstop Stop time for bolt preloading. 6

Default = 1030 (Real)

[ s ]


  1. The preloading tension stress is applied to the solid elements defined by the sect_ID. This can be used to preload a bolt modeled with solid elements.
  2. The sect_ID input is mandatory. Its normal vector (which is the local z direction of the section coordinate system) defines the preload direction in the bolt. The elements intersected by the cross-section are used to apply the preload.
  3. If Itype = 1, the uniform preloading stress is calculated using the preload defined force divided by cross-section initial area defined by the sect_ID.
  4. If Itype = 2, the preloading stress value applied to the elements of the section is user-defined.
  5. /TH/SECTION should be defined to output the preload force in the model.
  6. The preloading occurs at Tstart. The material stiffness of the elements defined by cross-section is reduced and a tensile stress is applied to the elements. The stress creates the preload force in the bolt. Next, the material stiffness of the preload elements is increased until it reaches its original values at Tstop time. Refer to Preload in the User Guide for more information.
  7. The resulting preloading force in the bolt can be less than the user-defined value. This is due to the initial deformation of the section elements or initial gaps between the parts being bolted.