I'm modeling a relatively complex geometry concrete beam in ATENA Science-GiD. In order to use the hexahedral mesh, I modeled the beam using smaller (all 6-sided prisms) volumes and connected those using a combination of shared surfaces and master-slave (fixed contact for surfaces) connections. All volumes are assigned the same material properties and mesh size. The mesh is assigned Mesh>Structured>Volumes>Assign size to volume lines. Mesh size is 2 inches for all geometry.

The results show cracking at some of the master-slave connections, mostly at corners. Is this caused by the master-slave connection, mesh settings, or something else? How can I fix?

Thank you for your help!