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Structural design of flexible culverts development trends

Pettersson L., Wadi A., Williams K.

Archiwum Instytutu Inżynierii Lądowej

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2017

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Nr 23

237--250

EN

Structural design requirements for flexible culverts are available in several international bridge design codes. Examples are the Canadian (CHBDC), the American (AASHTO) and the Swedish (TRVK Bro ll2). The designation “flexible culvert” may today be somewhat misleading. The word culvert is usually associated with small pipes in road embankments. However, over the years flexible culverts have grown bigger and a more proper designation would be bridges. Therefore, these structures are often also referred to as Soil-Steel Composite Bridges or just Soil-Steel Bridges. With this development also new and more stringent requirements on the structural design follows. In this paper key aspects of a holistic design approach based on the authors experience on the essentials of flexible culvert structural design3 are outlined and is compared to the current design approaches in the CHBDC and the TRVK Bro 11. However, this paper will provide insight into how the holistic design topics are addressed in current design codes and future research and development.

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Structural capacity of existing buried flexible culverts swedish design methodology

Pettersson L., Wadi A.

Archiwum Instytutu Inżynierii Lądowej

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2017

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Nr 23

229--236

EN

Knowing the structural capacity of existing bridges is essential for road administrations. This is equally true for flexible culverts as for any other type of bridge. For older structures all necessary data for a full detailed verification of the structural capacity may not be in place. In some instances the missing data may be possible to retrieve by different measurement and testing procedures in the field and in laboratory environment. However, for most of the structures one need to rely on database information when estimating the structural capacity. In this paper the procedures for estimating the structural capacity of existing flexible culverts specific for Swedish conditions is described along with some technical aspects important for the structural capacity.

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Recent research on flexible culverts in sloping terrain

Wadi A., Pettersson L.

Archiwum Instytutu Inżynierii Lądowej

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2017

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Nr 23

293--299

EN

The performance of buried flexible steel structures is directly influenced by the quality of the backfill soil and its configuration around the conduit. The economical choice of these structures stimulates practitioners to expand their different applications including their performance in sloping environment. The presence of steep surface slopes induces unbalanced loading and asymmetrical soil support around the conduit. This paper outlines the latest research efforts on how a flexible culvert would perform in sloping terrain environment. The paper focuses primarily on the structural behaviour of soil loading effects. The investigation highlights the use of numerical simulation in predicting the performance of a case study of flexible culvert under different construction schemes, where the influence of slope intensity and depth of soil cover are briefly presented. Soil slope stability as a major concern is also discussed. The research outcome clearly underlines the importance of soil configuration around steel culverts. The asymmetrical response of the conduit is predictably observed from the results and greatly influenced by the presence of shallow depth of soil covers. Sectional forces tend to increase with the increase of surface slopes. The results also underline the necessity of soil stability investigation when constructing flexible culverts in sloping terrain.

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Large-span soil steel composite bridges

Wadi A., Pettersson L.

Archiwum Instytutu Inżynierii Lądowej

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2017

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Nr 23

287--292

EN

Soil-steel composite bridges are considered competitive structures being an economical alternative to similar span concrete bridges. They are increasingly used for road and railway bridge construction. Spans have increased and structures with spans over 20 m have been built. The continuous development of infrastructure impels designers to push the limits of these structures for bigger spans with the lowest possible height of cover. Since the birth of the ring compression theory, different design methods have been developed to account for the various conditions and facilitate the use of bigger span structures. Yet, there is an urge to investigate whether the current design procedures are conservative or if they are reasonably accurate to predict the capacity of large-span structures. This paper presents the on-going project involving the capacity of large-span soil-steel composite bridges. The study investigates the use of finite element modelling in predicting the performance of a case study for an ultimate limit state field test. The project also highlights the need and intention to perform an ultimate limit state test for a large-span structure. The outcome of the project is to assess the current design procedures and to reflect recommendations on the design where seen applicable.