This is a simple model, so there shouldn’t be much more difference in the computational and hand calculation result. I have suggested some following points that might be helpful in investigating the issues clearly:
1. Please review the mesh quality and refine the mesh of the model.
2. Please check your point of application of the load and the other boundary conditions you have applied in the ansys.
You can also upload a screenshot of the model and hand calculations that you have performed. It would be helpful to investigate the differences in the results.
All the best