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Additional Information

See the adjacent Software Information links for general details regarding LUSAS Bridge software products and options.

Integral or Jointless Bridges

Brockhampton Road BridgeIntegral or jointless bridges are well known to eliminate the maintenance and salt corrosion problems associated with bridges having movement joints and bearings. However, the biggest uncertainty with the design of these types of structures is the reaction of the soil behind the abutments and adjacent to the foundation piles caused by seasonal thermal expansion of the various bridge components acting together. 

LUSAS Bridge, unlike some systems, allows you to accurately analyse the soil-structure interaction of the piles and bridge structure in one model and comprehensive results processing features give you with all the tools you need to view and interpret your results.

Integral Bridge Types

There are two main types of integral abutment bridge:

  • Those with short stub-type abutments that sit on piles and support the deck beams or slab.
  • Those with full abutment walls, sitting on piles, that retain the ground behind the wall as well as support the deck beams or bridge slab.

Overview

Integral bridges, or jointless bridges, as they are more commonly known in the USA, are constructed without any movement joints between spans or between spans and abutments. Typically these bridges have stub-type abutments supported on piles and a continuous bridge deck from one embankment to the other. Foundations are usually designed to be small and flexible to facilitate horizontal movement or rocking of the support. 

With integral bridges thermal deck movements are accommodated by soil structure interaction between the supporting piles and the surrounding strata. Deck loading is also affected by the soil which acts as both load and support system to the piles upon which the structures are founded. Specifying a series of spring supports along a pile to approximate soil behaviour is a commonly used modelling method when the structural load effects are the main item of interest. When the soil movement is of interest continuum models are used instead.

Integral bridges present a challenge for load distribution calculations because the bridge deck, piers, abutments, embankments and soil must all be considered as a single compliant system.

Whilst some analysis systems require you to use a pile design package to analyse the soil-structure interaction of the piles before passing results to and from the structural analysis design package, LUSAS Bridge handles it all within one analysis system - greatly simplifying your modelling and analysis.

Modelling and analysis with LUSAS Bridge

With LUSAS Bridge you can model and analyse integral abutment bridges in a number of ways:

  • 2D beam model with Winkler springs to represent the horizontal soil continuum.
  • 2D continuum model (plane strain) with staged construction and nonlinear materials for drained and undrained soil conditions.
  • 3D beam analysis with Winkler springs to represent the horizontal soil continuum.
  • 3D shell and beam analysis with Winkler springs representing the horizontal soil continuum.
  • 3D shell analysis with 3D (volume) continuum to represent the soil.
  • Full 3D analysis.

Integral abutment bridge model using 3D shells and beams with spring supports representing the horizontal soil continuum.

Integral abutment bridge model using 3D shells and beams with spring supports representing the horizontal soil continuum.

Viewing of results

The following results are from an analysis of a 3 span integral composite bridge comprising a concrete deck on steel girders with concrete diaphragms and abutments supported on H-piles.

In the USA, integral abutment bridges have been built since the 1960s and are increasingly being used for replacement structures. Lengths of integral abutment bridges are also increasing and now the state of Tennessee builds steel superstructure bridges up to 400 ft. (122m) long with no joints; and concrete superstructure bridges of this type up to 800 ft. (244m) and sometimes longer. One case in point is the bridge carrying Route 50 over Happy Hollow Creek - at a total length of 1,175 ft. (358 m), it is the longest, jointless, integral abutment bridge in the country. In the UK, the Highways Agency Departmental Standard, BD57, "Design for Durability", requires designers to consider designing all bridges with lengths of up to 60 metres and skew angles of less than 30 degrees as integral bridges. This advice is intended to prevent problems of joint leakage over supports and reinforcement corrosion that typically occur in non-integral forms of bridge construction.

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Software Information

  Bridge / Bridge plus
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green_arrow.gif (94 bytes) Staged construction modelling
green_arrow.gif (94 bytes) Geotechnical / Soil-structure modelling
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  Bridge LT
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  Additional Information
green_arrow.gif (94 bytes) Linear and nonlinear buckling analysis
green_arrow.gif (94 bytes) Curved girder analysis
green_arrow.gif (94 bytes) Integral or jointless bridges
green_arrow.gif (94 bytes) Post-tensioning
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