Monitoring of a Swedish Integral Abutment Bridge
Abstract One of the most commonly discussed problems regarding bridges with integral abutments is the influence of longitudinal elongation of the superstructure as a result of seasonal temperature variations. A bridge built with integral abutments is often supported by a row of piles made of steel or concrete. The longitudinal elongation of the superstructure induces a displacement and a rotation at the top of the pile, which in turn may cause strains that exceeds the yield strain. Such seasonal variations may lead to low-cyclic fatigue failure in the pile. Therefore, it is of great interest to investigate the amplitude of these strains, as well as the general behaviour of the bridge. In 2005, the European R&D project, INTAB (RFSR-CT-2005-00041, “Economic and Durable Design of Bridges with Integral Abutments, 2005–2008”) was started. Within the INTAB project a composite bridge was built and monitored in Northern Sweden.
Numerical Analysis of the Behavior of an IPM Bridge According to Super-Structure and Sub-Structure Properties
A bridge with an integrated and pile-bent abutment with a mechanically stabilized earth-wall (IPM) was developed by separating earth pressure from the abutment to overcome the problems typically faced by integral abutment bridges. Also, the IPM bridge removes expansion joints and bearing by integrating the super-structure and the abutment and does not need many piles because it separates the earth pressure from backfills. Therefore, it is superior in cost, durability, and maintainability to traditional bridges and is sustainable due to using less material. A numerical analysis was conducted to ascertain the behavior of the IPM bridge according to its super-structural and sub-structural characteristics. Based on the analysis results, the behaviors of the IPM bridge are as follows: The bending moments ( 
 M 
 y 
 ) 
 of the pre-stressed concrete (PSC) girder and the steel-plate girder of the bridge were influenced by the presence of the time-dependent loads. The contraction behavior in the PSC girder is largely due to the time-dependent loads, whereas the expansion behavior in the steel-plate girder is large due to its greater thermal expansion coefficient and temperature range compared with those of the PSC girder. In general, the suggested bridge length limit for PSC girders in both the integral abutment bridge and the IPM bridge is larger than that in a steel bridge. This needs to be reviewed again with consideration of the long-term and seasonal behaviors.
Representative values of thermal actions for concrete bridges
The pre-standard ENV 1991-2-5 Thermal Actions was concluded in 1996 and deals with the thermal actions induced in the structures due to climatic effects (air temperature, solar radiation). These climatic conditions cause a non-linear temperature profile through the depth of the bridge deck. This profile can be subdivided into three parts which are called ‘thermal actions’: bridge effective temperature, linear temperature difference, non-linear part. For concrete bridges the first two parts play the most important role. According to pre- standards ENV 1991-1 Basis of Design thermal actions are defined as variable actions and following representative values have to be determined: –characteristic value, with return period of 50 years; –infrequent value, with return period of one year; –frequent value, with return period of two weeks; –quasi-permanent value Three groups of bridge cross sections are investigated: box girders, T-girders, slabs. 
 
 
 
The climatic data were obtained from the meteorological station Giessen (Hessen, Germany). This station located in the centre of Germany and Europe and can be considered as a representative place for middle Europe. The record period is from 1981 to 1990. 
 
 
 
To exclude the problem of autocorrelation the three-day maximum of climatic effects and extreme value distribution type III are used for statistical analysis. Then the representative values of climatic effects are calculated. 
 
 
 
For calculation of temperature profile the one-dimensional heat flow model through concrete bridge deck is used. This model runs off for four different representative values of climatic effects. Afterwards four representative values for uniform temperature component and for linear temperature differences are obtained. The reduction coefficients Ψ are also calculated. The characteristic values of thermal actions are included in the document ENV 1991-2-5 Thermal Actions and the Ψ coefficients are included in the document ENV 1991-3 Traffic Loads on Bridges.