The Structural Engineer > Archive > Volume 84 (2006) > Issues > Issue 18 > Extreme shade air temperatures to be used in structural design
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Extreme shade air temperatures to be used in structural design

The Eurocode on thermal actions, BS EN1991-1-51 has now been published and the accompanying National Annex for implementation of the Eurocode in the UK has been issued for Public Comment2. The National Annex contains the appropriate extreme shade air temperature maps to be used for design against thermal actions, an important, and in some conditions governing, loading case in the design of bridges. Recent sustained warming of the UK climate might be expected to have increased the severity of extreme high temperature events and reduced the severity of extreme low temperature events. Accordingly a limited exercise was commissioned by the Highways Agency to investigate whether extreme shade air temperature maps that were developed in the 1970s, based on data from 1941–1970, would still be appropriate for current designs. Based on a limited selection of six UK stations, estimated maximum shade air temperatures corresponding to a return period of 50 years, based on data period 1975–2004, are typically ~0 to 1°C higher than those based on 1941–1970. For once in 50-year minimum values the overall warming is rather more pronounced but the results more scattered, typical increases being ~0 to 2°C. It is thus concluded that, for the purposes of BS EN1991-1-5, maps produced using data from 1975-2004 would be insignificantly different from the existing maps. UK mean shade air temperatures have recently (since about 1985) increased noticeably, from which it seems likely that the extreme value projections from the analysed period 1975-2004 are already out of date with respect to the current decade’s climate. Furthermore, an overwhelming consensus of climate change modelling predicts continued warming over coming decades. It is therefore suggested that an allowance should be made for any future trends by applying a factor to the extreme shade air temperatures, which is reviewed every 10 years. J. Fullwood, BSc(Hons) Applied Scientist, Meteorological Office, Exeter B. W. Smith, BA, MS, FREng, FICE, FIStructE FASCE Consultant, Flint & Neill Partnership, London

Author(s): Fullwood, J;Smith, B W

Keywords: eurocode1;united kingdom;temperatures;shade;air;Bridges;data;comparing