Pont en treillis

Résumé

vignette|Pont Bailey sur la Meurthe, France. Pont provisoire en treillis, à mise en place très rapide. Un pont en treillis, pont en poutre en treillis ou pont-treillis est un pont dont les poutres latérales sont composées de barres métalliques triangulées, assemblées en treillis. Au début du , les poutres en treillis étaient dénommées poutres américaines, car c’est aux États-Unis que la technique est apparue. Les treillis peuvent être assemblés par boulonnage, par rivetage ou bien soudés. Il s’agit d’une méthode de construction rapide et peu coûteuse. Le concept a été mis au point par Andrea Palladio. Descriptif vignette|350px|Terminologie d'une poutre en treillis (de type Pratt). Les éléments horizontaux supérieurs et inférieurs du treillis constituent les « membrures » supérieures et inférieures. Pour le calcul, on parle également de « cordes » supérieures et inférieures. Ces membrures, ou cordes, sont constituées chacune par une seule poutre rectiligne (bien que certai

Source officielle

https://fr.wikipedia.org/wiki/Pont_en_treillis

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Conceptual design of 1000 m scale steel-UHPFRC composite truss arch bridge

Xiujiang Shen, Ping Zhu

Excessive self-weight and difficulty in construction are the main issues confronted by super-long-span arch bridges. To address these issues, a conceptual design of steel-ultra-high performance fibre-reinforced concrete (UHPFRC) composite truss arch bridge with a main span of 1000 m was proposed, and the corresponding structural responses were numerically investigated based on finite element analysis (FEA) in this study. In this proposal, the UHPFRC was applied to box arch ribs for bearing the large axial forces, and the steel was used for web members and transversal connectors to avoid the risk of cracking. Such composite arch bridge has a much lower self-weight than traditional concrete arch bridges and avoids the need for welding on thick steel plates since only thin steel elements (thickness not exceeding 40 mm) are used compared to steel arch bridges. The cantilever erection with cables support was adopted during the main arch erection. In this scope, the temporary erection cables merely need to bear the self-weight of two truss arches and the transversal connectors during each closure and the process is repeated four times, which thus reduces largely the cost of temporary supports for construction and increases the feasibility of the construction. Based on the FEA results, the UHPFRC arch ribs are always in compression at a maximum compressive stress of 63.8 MPa. Furthermore, the stability, stress, and stiffness of each component during each construction stage meet the requirements of the code. By the comparative studies of the steel arch bridges, UHPFRC arch bridges, and the proposed one, the steel-UHPFRC composite truss arch bridge has significant technical and economical advantages and is suitable for a bridge with a main span in the range of 500 similar to 1000 m.

ELSEVIER SCI LTD2021

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This paper describes new optimization strategies that offer significant improvements in performance over existing methods for bridge-truss design. In this study, a real-world cost function that consists of costs on the weight of the truss and the number of products in the design is considered. We propose a new sizing approach that involves two algorithms applied in sequence -(1) a novel approach to generate a "good" initial solution and (2) a local search that attempts to generate the optimal solution by starting with the final solution from the previous algorithm. A clustering technique, which identifies members that are likely to have the same product type, is used with cost functions that consider a cost on the number of products. The proposed approach gives solutions that are much lower in cost compared to those generated in a comprehensive study of the same problem using genetic algorithms (GA). Also, the number of evaluations needed to arrive at the optimal solution is an order of magnitude lower than that needed in GAs. Since existing optimization techniques use cost functions like those of minimum-weight truss problems to illustrate their performance, the proposed approach is also applied to the same examples in order to compare its relative performance. The proposed approach is shown to generate solutions of not only better quality but also much more efficiently. To highlight the use of this sizing approach in a broader optimization framework, a simple geometry optimization algorithm that uses the sizing approach is presented. This algorithm is also shown to provide solutions better than the existing results in literature. (c) 2007 Elsevier Ltd. All rights reserved.

2007

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Evaluating two model-free data interpretation methods for measurements that are influenced by temperature

Irwanda Laory, Ian Smith, Ngoc Thanh Trinh

Interpreting measurement data to extract meaningful information for damage detection is a challenge for continuous monitoring of structures. This paper presents an evaluation of two model-free data interpretation methods: moving principal component analysis (MPCA) and robust regression analysis (RRA). The effects of three factors are evaluated: (a) sensor-damage location, (b) traffic loading intensity and (c) damage level, using two criteria: damage detectability and the time to damage detection. In addition, the effects of these three factors are studied in situations with and without removing seasonal variations through use of a moving average filter and an ideal low-pass filter. For this purpose, a parametric study is performed using a numerical model of a railway truss bridge. Results show that MPCA has higher damage detectability than RRA. On the other hand, RRA detects damages faster than MPCA. Seasonal variation removal reduces the time to damage detection of MPCA in some cases while the benefits are consistently modest for RRA.

Elsevier2011

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