This warning, during a pushover analysis, usually points to convergence issues, which may indeed stem from the transverse (u2) direction load case parameters. Here are some recommendations: 1. Verify that the mode shape selected for the pushover load case significantly contributes in the transverse direction (u2). If the mode shape primarily responds in a different direction, it may cause instability or ineffective load application in u2. 2. Review the load distribution in the transverse direction. Try using a different load distribution pattern if the current one doesn't represent the bridge’s expected response accurately. 3. Set an appropriate maximum displacement to allow the structure to reach higher load levels. Meanwhile, reducing load increment steps in the pushover load case can improve convergence, especially if your structure is behaving nonlinearly in the u2 direction. 4.Try adjusting the convergence tolerance (with caution), if the above adjustments don’t solve the issue; a slight increase could help the solver find equilibrium. 5. Double-check your hinge properties and their placement. Inadequately defined or overly stiff hinges in the transverse direction may cause convergence issues. 6. Make sure your model is stable in the transverse direction, with adequate mass participation and constraints. Remember to monitor convergence behavior and null steps closely as you apply these adjustments.

Good luck!