## 5 Numerical Simulation of the Long-Term Behavior of a Bridge  
The bridge is of the \"balanced cantilever girder\" type, built with segments cast from piers with mobile equipment, and it is characterized by a central 155 m span (the longest span in Romania for prestressed concrete box girder bridges), with two side symmetric spans of 77.5 m (see Figure 11). The deck has a varying depth provided by a curved softit of parabolic shape. The depth of cross section varies from maximum value of 10 m at the pier axis, to a minimum value of 2.4 m, at mid span and at the abutment supports. The upper slab is 14.75 m wide and transversally inclined of 2.5% (see Figure 12). Figure 11: Picture of the bridge during its construction. Figure 10: **(a)** Evolution of the force in the prestress steel tendon for different loading conditions; (**b–d**) evolution of the normal stresses in the middle-span cross-section for the prestress action only, the point load only, and the both of them, respectively. The layout of the post tensioned internal tendons (total length 10 km/single deck), follows the upper and lower slabs (see Figure 12). The upper tendons counterbalance the action of the free cantilever under gravity loads. The lower tendons are located along bottom slab and anchored to reinforced concrete internal blisters. The layout is symmetric with respect to the midlength of the central span both for the central and the side spans. The bridge deck is supported by two piers and two abutments through two seismic bearings at each support. The bearings are of the \"friction pendulum\" type, which develop friction forces both in static conditions, due to static forces and small displacements, and dynamic condition providing dissipation. Under seismic loads (moderate for that construction site) the whole concrete structure develops only elastic behavior, because dissipation and lengthening of the natural period of the structure are provided by the seismic bearings. Piers 1 and 2 are characterized by same shape but different height, respectively, 17.4 m and 16.15 m. The pier has a hollow rectangular cross section with 8 m transverse and 6 m longitudinal external dimensions and a massive head capital at the top. The piers base sections are connected to a reinforced concrete massive rectangular footing erected on a ring of diaphragm walls capable of transferring to a deep ground level the forces coming from the superstructure. Both abutments are spill-through type. The beam seat is supported by a number of shear walls aligned with longitudinal deck axis. Each shear wall is founded on deep diaphragm walls that transfer to the deep ground level load due to superstructure and earth pressures. The design of the viaduct was carried out taking into consideration many advanced issues, including creep and shrinkage deformations and seismic behavior. A finite element numerical model of the prestressed concrete deck, capable of simulating more than thirty construction phases was implemented with specific software. The long-term behavior was studied accurately by means of an experimental/numerical procedure which is presented in this paper. Because of piers low ductility capacity, the the seismic protection was achieved by integral isolation through \"friction pendulum\" devices that develop dissipation by friction mechanism. These type of seismic bearings show many advantages in term of cost/performance in comparison with traditional high dissipation rubber bearings, mainly if they sustain high level of axial loads (as it is in this case, 40,000 kN/each pier bearing, 170 cm diameter). Dynamic tests of \"friction pendulum\" bearing devices have been performed at SRMD lab, University of San Diego (USA) [41]. The detail project of foundation design  
Figure 12: Project description: Upper view and longitudinal sections. was developed in collaboration with Technodata (Naples). Design assistance in the construction field, was developed with constant support by Italrom (Bucharest, affiliate company of Lombardi-Reico).