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.