Abstract
The structural optimization method of steel cantilever used in concrete box girder bridge widening is illustrated in this paper. The structural optimization method of steel cantilever incorporates the conceptual layout design of steel cantilever beam based on the topological theory and the determination of the optimal location of the transverse external prestressed tendons which connect the steel cantilever and the box girder. The optimal design theory and the analysis process are illustrated. The mechanical model for the prestressed steel cantilever is built and the analytical expression of the optimal position of the transverse external tendon is deduced. At last the effectiveness of this method is demonstrated by the design of steel cantilevers which are used to widen an existing bridge.
Highlights
Structural optimization is an important tool for structural designers because it allows the designers to tailor a structure to a specific performance level required by the owner
The structural optimization method of steel cantilever used in concrete box girder bridge widening is illustrated in this paper
In order to ensure that the steel cantilever and original girder are reliably combined, principles of the stress on the interface between steel cantilever beam and concrete postpouring diaphragm should be confirmed as follows: the key regions of concrete postpouring diaphragm interface which are under the base plate at web, roof, and bottom flange plate as shown in Figure 15 should keep in compression to avoid from being separated from steel cantilever and the maximum compressive stress of concrete interface should be ensured not to exceed local compressive admissible value of postpouring diaphragm concrete
Summary
Structural optimization is an important tool for structural designers because it allows the designers to tailor a structure to a specific performance level required by the owner. Steel cantilever widening concrete box girder method is a new box girder widening method without piers, which has many advantages, such as shorter construction period, open clearance of span, lesser traffic interference, better traffic capacity, and better economic benefit [17, 18] According to this method, the original bridge deck is widened by the orthotropic steel decks that are laid on the cantilevers (Figure 1). Pairs of steel cantilever beams are installed on both sides of the original box girder at regular distance (L, see Figure 2) As it is shown, postpouring concrete diaphragms are used to connect with the newly added steel cantilever beams. The topic of this paper is a structural optimization problem which incorporates the conceptual layout design of the steel cantilever and the determination of the optimal location of the transverse external prestressed tendons. The analytical expression of the reasonable acting position of the transverse external prestressed tendons on the steel cantilever is deduced and the steel cantilever structural optimization scheme is proposed
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