This article deals with the challenges of semi-integral construction of long viaducts.The main characteristic of semi-integral bridges is the monolithic connection of mostparts of the substructure with the superstructure. This leads to complex load-bearingbehavior, in which several structural components interact with each other. Because ofthe longitudinal movement of the superstructure, constraint forces and moments occurin the piers. They induce additional stresses in the structure compared to convention-ally supported bridges. An important issueduring the design process is the choice ofthe pier cross section. The stiffness and ductility of the piers influence the constraintmoments and failure behavior of the pier. This is the reason why the detailed investi-gation into the influencing parameters (normal-force utilization, reinforcement ratio,and width-to-height ratio) described in this paper was carried out. In this investigation,the moment–curvature relationship was used and the failure behavior as well as theconstraint moments in the structure were evaluated.