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During construction phases, the bearing fixities may need to be redefined or overridden with new definitions.

For instance, in the case of Precast I-Girders with diaphragms (where diaphragms are constructed at a different stage, subsequent to girder construction), the Rx value may change accordingly. In such cases, Rx should be defined as 'Fixed' or with a high stiffness value due to stability concerns. After diaphragm construction, Rx (rotation along the X-axis) can be redefined as 'Free' or with a lower stiffness value. These definitions are crucial for accurately modeling the real-life structural behavior of bridge structures and can be handled using this section of the workflow.

Another example is the presence or absence of temporary supports, where each scenario may require different fixity definitions. This section can be used to address those variations.

Superstructure Connection Change

Stage: Define the stage at which the fixity definitions will be overridden. The selected stage and subsequent stages will apply the fixity definitions based on the input provided for this section.

Insertion Points: Used for specifying the bearing location.

Tx[kip/in][Fixed/Free/Stiffness]: When the bearing rotation is 0 degrees, the stiffness in the longitudinal direction is represented by tx. It is typical for a continuous girder to have at least one fixed bearing (or use a real stiffness value) in the tx direction.

Ty [kip/in][Fixed/Free/Stiffness]: The stiffness in the transverse direction is represented by ty when the bearing rotation is 0 degrees.

Tz [kip/in][Fixed/Free/Stiffness]: Tz represents the stiffness in the vertical direction, and it is common to use a high stiffness value such as 1000 kip/in or a fixed.

Rx[kip-in/rad][Fixed/Free/Stiffness]: To address stability concerns, a small RX stiffness can be used in the torsional direction (Rx) under certain conditions. If the constructed girders are not connected with bracings to other girders at any stage, it can result in stability issues. Therefore, to overcome this problem, a small RX stiffness is recommended.

Ry[kip-in/rad][Fixed/Free/Stiffness]: Typically, bearings are free to rotate in Ry direction.

Rz [kip-in/rad][Fixed/Free/Stiffness]: Typically, bearings are free to rotate in Rz direction.