Kempis Chuspita I Viaduct

The Kempis Chuspita Viaducts are three viaducts (724, 699, and 1382 meters long) with two separate decks (each 15.20 m wide) separated, formed by post-tensioned precast concrete segments. The total length of the decks is of the order of 5,560 meters, divided into 141 spans spanning between 34 and 52 meters; the minimum horizontal radius of curvature is 450 m, and the height of the piers varies from 1.5 to 33 meters.

The Rómulo Betancourt Highway or Autopista de Oriente, is a large project that aims to communicate the northeastern states of Venezuela, with the center and capital of the Republic, through 280 km of modern and functional roads, combining conventional earthworks, with elevated structures, tunnels and river channeling. The Kempis Chuspita section, 8 km long, has a very rugged topography with a river channeled into a narrow winding valley with a slope of up to 2%, which is why the canalization was discarded and a typical modern alpine road adopted, reduced cuts in the slopes and large viaducts.

The geological conditions and topography determined throughout the project a great diversity of foundation types: Deep, by means of excavated and concreted piles "in situ" or by means of concreted piles; Direct foundations with large isolated footings, semi-deep foundations such as solid circular shafts and hollow shafts filled with granular material from the site. Stirrups are conventional.

The superstructure connects to the abutments by high-strength bars that prevent longitudinal displacement, as well as cast-in-place keys that prevent transverse displacement and rests on two neoprene plates with steel/Teflon sheeting to allow for the required expansion.

The piles are octagonal (irregular octagonal hollow sections) of 5.00 x 2.50 m and 0.40 m thick walls. In areas where the piers interfere with the riverbed, special structures, portico or monopiles were built, the latter consisting of a macro column of irregular octagonal section and a double cantilever beam of variable section. At the top of each pile, a capital was placed to transmit the loads from the superstructure to the infrastructure and on which the neoprene supports are placed. Each capital, 1.50 m high, has a recess where a shear key, prefabricated, is placed to prevent horizontal displacements.

The 2.50-meter high and 15.20-meter wide deck is made of prefabricated segments. A total of 1,681 typical segments and 282 pier and joint segments were manufactured using the short line method, which consists of using the already-cast segment as formwork on the face of the segment being built, allowing for perfect coupling between successive segments. In the assembly of the viaducts, the section-by-section method was used, always working from the deck, a necessary condition due to the ruggedness of the topography. For the placement of the segments, a self-launching shoring system was designed, which rests on the piers and makes it possible to assemble sections up to 52 meters long without intermediate support. The assembly begins with the farthest pier segment, which is taken to its final position using a pair of winches located at the end of the shoring system; this activity is repeated until the last typical segment is placed. Once the segments of a section have been placed, they are leveled, and the sheaths for the longitudinal post-tensioning cables are placed.