Finite element model updating of a tied-arch bridge using Douglas-Reid method and Rosenbrock optimization algorithm

Abstract Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element (FE) model updating method is often applied. This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas-Reid method in combination with Rosenbrock optimization algorithm. Based on original drawings and topographie survey, a FE model of the investigated bridge is created. Eight global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Then, eight structural parameters are selected for FE model updating procedure through sensitivity analysis. Finally, the optimal structural parameters are identified using Rosenbrock optimization algorithm. Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies, they may not be the optimal variables which minimize the differences between numerical and experimental modal data. However, a satisfied agreement between them is still presented. Hence, FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures

An innovative steel-concrete joint for integral abutment bridges

Integral abutment bridges are becoming rather common, due to the durability problems of bearings and expansion joints. At the same time, among short- and medium-span bridges, multi-beam steel-concrete composite deck with hot-rolled girder is an economical and interesting alternative to traditional pre-stressed concrete solutions. The two concepts can be linked together to design integral steel-concrete composite bridges with the benefits of two typologies. The most critical aspect for these bridges is usually the joints between deck and piers or abutments. In this paper, an innovative beam-to-pier joint is proposed and a theoretical and experimental study is introduced and discussed. The analyzed connection is aimed at combining general ease of construction with a highly simplified assembly procedure and a good transmission of hogging and sagging moment at the supports in continuous beams. For this purpose, the traditional shear studs, used at the interface between steel beam and upper concrete slab, are also used at the ends of steel profiles welded horizontally to the end plates. To better understand the behaviour of this kind of joints and the roles played by different components, three large-scale specimens were tested and an FE model was implemented. The theoretical and experimental results confirmed the potential of the proposed connection for practical applications and indicated the way to improve its structural behaviour

3D tubular mesh as a girder for bridge design

The following paper will present a spatial tubular solution adopted for the design proposed for the new Langensandbrücke in Luzern-Switzerland. The image of the city of Luzern is linked to those of its famous covered bridges and the layout of the structure was conceived as a modern interpretation of wooden structure covering the renowned Kapellbrücke. Therefore the occasion to propose a main structure composed by a couple of truss girders formed by a number of inclined steel rings of different diameters able to hold inside a cycle track and the pavement for pedestrians and to support centrally the 5 lanes road on a total span of 80m. To support the simple even if non conventional conceptual design an accurate finite element analysis was performed on the structure to assess its stress state, its stiffness under design loads and its overall reliability. The design proposed reveals a strong symbolic value with non conventional structural solutions

Curved shell-supported footbridges

After Maillart's curved bridges, the improved building technologies in structural concrete and steel work led designers to realize different typologies of curved bridges. Jörg Schlaich's contribution in the design of curved bridges has been fundamental, through developing different typologies of suspended and cable-stayed curved bridges. In the '60s of the past century, Sergio Musmeci gave another innovative contribution to bridge design, by shaping shell supported bridges with minimal shell surface, and finally realizing the Basento Bridge in Potenza, Italy, a concrete shell bridge considered as his masterpiece. Accounting for Schlaich's and Musmeci's work on, respectively, curved and shell bridges, a curved footbridge supported by an anticlastic concrete shell with minimal surface is herein studied. The influence of the boundary conditions on bridge shape, and the advantages of prestressing the ring girder supporting the cantilevered deck are studied

Tensegrity bridge with prestressed deck

In this paper, structural analysis and design of a tensegrity bridge with prestressed deck is introduced. As a matter of fact, cable pretension results in prestressing of the deck. Nonlinear geometric effects, key load cases, influence of main cable's rise and modal analysis of this type of structure is studied by finite element method. The structural behaviour of the tensegrity bridge appears to be suitable for a footbridge, although peculiar with respect to traditional footbridges. Some suggestions about structural design, material properties and structural behaviour are summarized

The optimal shapes of piles in integral abutment bridges

Integral abutment bridges (IABs) can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possibilities were considered and compared: (a) a pile with two different diameters along the depth and (b) a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into pre-deep holes filled with loose sand. Finally, the case of super-long integral abutment bridges (L = 500 m) with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization cases were considered with similar study criteria as the Isola della Scala Bridge: (a) a pinned pile head for semi-integral abutment, (b) a fixed pile head without a pre-hole, (c) a fixed pile head with a pre-hole of any depth, (d) a fixed pile head of a pre-hole with a depth limit (< 2 m) allowing for enough embedded length for the friction pile. The case studies confirmed the potential of the proposed optimization techniques for finding the optimal shape of piles in integral abutment bridges

Cable optimization of a cable-stayed bridge based on genetic algorithms and the influence matrix method

Structural optimization is an important tool for structural designers that helps them to find innovative design solutions and structural forms with a better exploitation of materials as well as decreased self-weight and minimum material costs. In this article, a design procedure coupling the influence matrix method and genetic algorithms to optimize stay cables in cable-stayed bridges is presented. Following that, the design procedure is utilized in the preliminary design of a twin towers double-cable planes cable-stayed bridge to be located in Ferrara, Italy. The cable cross-sectional areas and corresponding pre-tension forces are optimized simultaneously. The results demonstrate that the proposed procedure is a powerful tool for designing stay cables and predicting the optimum cross-sectional areas of stay cables under certain stress and displacement constraints