@misc{9249569,
  abstract     = {{Portal frame bridges are common in Sweden and are continuously subjected to temperature variations. These variations give rise to restraint forces when the structure is prevented from moving freely during thermal expansion or contraction. Previous studies indicate that the amount of reinforcement in portal frame bridges has increased substantially over the past 50 years, which can partly be attributed to stricter requirements for three-dimensional modelling as well as changes in design standards. At the same time, clear guidelines are lacking in both the Eurocodes and the Swedish Transport Administration regarding how temperature actions should be modelled and which temperature distributions ought to be considered in three-dimensional analyses.

This study aims to analyse how temperature actions influence the reinforcement demand in portal frame bridges and to examine the effects of different temperature load cases, creep, and boundary conditions.

The investigation was carried out using finite element analysis, where geometric dimensions and material properties were implemented in a model of a reference bridge located in Falkenberg. The portal frame bridge was modelled in BRIGADE Plus with load cases both including and excluding temperature actions. Minimum reinforcement and reinforcement required for crack-width control were subsequently calculated based on the results extracted from the deck slab.

A comparison between reinforcement demand with and without temperature actions indicates that the additional reinforcement required due to thermal effects is significantly larger in the transverse direction than in the longitudinal direction. For the studied reference case, the minimum reinforcement calculated in the serviceability limit state also results in a greater transverse reinforcement demand than that obtained in the ultimate limit state. Revised guidelines regarding minimum reinforcement may therefore be perceived as one of the reasons behind the increased amount of reinforcement placed in modern bridges, particularly when this reinforcement is governed by pure tension. Minimum reinforcement under pure tension implies that, in some cases, no crack-width calculation is required for the existing bridge.

To reduce the reinforcement demand, especially in cases where temperature differences between bridge components are governing, a temperature difference of 10 °C between the deck slab and the frame legs, instead of 15 °C, can lead to a noticeable reduction. At a temperature difference of 5 °C, this reduction becomes even more pronounced.}},
  author       = {{Shaheen, Diana}},
  issn         = {{0281-6679}},
  language     = {{swe}},
  note         = {{Student Paper}},
  series       = {{TVSM-5000}},
  title        = {{Modellering av temperaturbelastade plattrambroar - utvärdering av tvångslaster och armeringsbehov}},
  year         = {{2026}},
}