You can apply an axial load or a combination of torque and a friction factor to simulate the prestress condition of a bolt connector. Enter the values under Pre-load in the Connector Bolt PropertyManager
For static studies, bolt connector definitions induce two successive analysis runs:
- For the first analysis run, the program applies the user-defined pre-load value to prestress the bolt connectors.
All other types of loads are suppressed. After the analysis completes, the program calculates the
tensile force of each bolt which it compares to the user-defined pre-load value.
- The program calculates a new adjusted pre-load value based on the difference between the tensile force and the user-defined pre-load value.
- The program runs the analysis once again with all the loads and the internally adjusted pre-load value for each bolt connector.
The first analysis run should typically include all loads that are present before the bolts are tightened. Such loads typically include gravity, but can also include all the loads representing the state of stress when the bolts are tightened (forces, thermal loads, spring pre-loads, etc.)
It is not currently possible to select which loads to include in the first analysis where the program calculates the new adjusted pre-load value.
For most cases, this limitation should have no major impact on the accuracy of the results.
In nonlinear analysis, there is no adjustment of the user-defined pre-load. The pre-load is considered during the first time step of the analysis.
If you use symmetrical bolts, enter the total pre-load value and ½ or 1/4 of the total mass of the bolt according to the selected symmetry type. Also, when you list bolt forces for symmetrical bolts after running a study, the results equal ½ or 1/4 of the total force.