Diseño, asistido por ordenador, de tableros de puentes losa

CAD of slab bridge decks

A program is presented for the automatic design of slab bridge decks. The bridges must meet the following conditions: - The plant must be trapezoidal with parallel free borders an constant cross-section (width and height). - The profile of the cross-section may be trapeziodal with two additional wings of variable height. Simpler forms as trapezoidal with two vertical borders or rectangular are particular cases of the general shape. - The cross-section may be either solid or hollow, the hollow being either circular or rectangular. Two wnd hollows smaller than the central ones may also be considered. - The support lines may be made solid either by filling the hollows or by building a rectangular cross-section; the length of this solid zone may also be chosen. The bridge is defined by means of a minimum nmumber of geometrical data which the program automatically places the hollows and draws the plant and the cross-section. Data can be interactively changed in order to obtain a satisfactory configuration. The program draws and marks the plant and the cross-section. In the plant the support lines, the hollows, and the hidden edges of the bridge are drawn using different types of dotted lines and dashes. Some additional values such as the hollow ratio and the depth of the centre of gravity are displayed together with the cross-section. The program automatically defines a grid for the calculation of deflections and load effects. The characteristics of this grid may be subsequently changed by the operator. The porogram computates the cordinates of the nodes and the topological and mechanical description of the members and allows the definition of the support conditions. Then the load cases and their combinations may be defined, including self-weight, dead load, uniformly distributed load, concentrated loads of the vehicle in accordance with the Spanish regulations for road bridges, and the prestressing loads. With these data the deflections and load effects are evaluated. With the results obtained the program may calculate the reinforcement which can be displayed graphically and numerically. Some examples are also presented.