Lisø PhD Dissertation Manuscript - NTNU
Lisø PhD Dissertation Manuscript - NTNU Lisø PhD Dissertation Manuscript - NTNU
accelerated frost damage or frost decay for the thirteen stations, from highest to lowest, as presented in Table 2 and illustrated in Fig. 4. A high frost decay exposure index (FDEI) value indicates a high risk of frost decay or frost damage. Annual average number of days with freezing point crossings (FPC) 100,0 90,0 80,0 70,0 60,0 50,0 40,0 30,0 20,0 10,0 0,0 Kristiansand (Kjevik) Bergen Bodø Trondheim (Værnes) Ørland Stavanger (Sola) Ålesund (Vigra) Fig. 4. Frost decay exposure index (FDEI) for the thirteen example stations, presented in a combination diagram. The annual average number of freezing events is given in columns, with values on the left side axis. Values for the resulting average year total frost decay exposure index (see line) are given on the right side axis. Weather data for the reference 30-year period 1961 – 1990 is used, summing 4-day rainfall prior to freezing events. The results can be assessed qualitatively as follows: Kristiansand and Bodø, on top of the list for both 2-day, 3-day and 4-day sums of rainfall prior to freezing events, have large amounts of rainfall coupled with a sizable number of freezing events per year, and therefore represent the highest frost decay potential. Lastly, Røros and Karasjok have a high number of freezing events, but a very small average rainfall, especially in winter months. A few localisations are changing one place on the ranking dependent on the number of days of rainfall counted. Bergen is especially to be noted, as it climbs from number five when summing 2-day rainfall to number 2 on the ranking when summing 4day rainfall, in particular due to extreme amounts of rain. Still, the bottom four localisations on the ranking are independent of the number of days of rainfall summed prior to days with freezing point crossings. This also applies for the top four localisations on the ranking, when Bergen is left out of account, indicating a robust method of characterising climates to promote frost decay. Damaging rain penetration in porous, mineral building materials requires a long-lasting absorption of moisture. Subsequent and repeated freezing events may destroy the material, or contribute to accelerated decay and thus reduced lifetime, if the water content is higher than the critical degree of saturation for the material at the time of freezing. Tromsø Page 8 of 13 Fruholmen Lyngdal Oslo Røros Karasjok 800,0 700,0 600,0 500,0 400,0 300,0 200,0 100,0 0,0 Frost decay exposure index (FDEI)
The frost decay exposure index (FDEI) is thus defined as the accumulated annual average sum of 4-day rainfall prior to days with freezing events. A 4-day spell of rainfall is shown to provide a reliable basis for climate differentiation of frost decay risk. A national map of the calculated frost decay exposure indices is presented in Fig. 5, based on climate records for 168 weather stations in Norway and summing 4-day rainfall ahead of freezing events. Fig. 5. Frost decay exposure index (FDEI) map for Norway: relative potential for a climate to accelerate frost decay or promote frost damage. Weather data for the reference 30-year period 1961 – 1990 is used, summing 4-day rainfall prior to freezing events. Page 9 of 13
- Page 91 and 92: construction industry, and academic
- Page 93 and 94: BUILDING RESEARCH &INFORMATION (JAN
- Page 95 and 96: greater variations (Lisø et al., 2
- Page 97 and 98: Typical problem areas and recommend
- Page 99 and 100: Figure 3b Recommended design of win
- Page 101 and 102: Figure 7 Example showing the recomm
- Page 103 and 104: Figure 11a Poor solution for a £as
- Page 105 and 106: Acknowledgements This paper was wri
- Page 107 and 108: Climate adapted design of masonry s
- Page 109 and 110: 2. Masonry defects in Norway 2.1. S
- Page 111 and 112: Fig. 2. Example illustrations of th
- Page 113 and 114: The presented results are in good a
- Page 115 and 116: appropriate in a more severe type o
- Page 117 and 118: screen in a two-stage weatherproofi
- Page 119 and 120: INCREASED SNOW LOADS AND WIND ACTIO
- Page 121 and 122: The hurricane (Beaufort number 12)
- Page 123 and 124: The extensive revisions of the code
- Page 125 and 126: The number of buildings investigate
- Page 127 and 128: As is apparent from the values in t
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- Page 131: TABLE 3. Summary of findings Struct
- Page 134 and 135: Lisø, K.R./ Building envelope perf
- Page 136 and 137: temperature of -4°C or less. See F
- Page 138 and 139: Today, frost resistance of brick, c
- Page 140 and 141: degree of saturation, freezing will
- Page 144 and 145: A possible objection to the present
- Page 146 and 147: [17] Dührkop H., Saretok V., Sneck
- Page 149 and 150: Decay potential in wood structures
- Page 151 and 152: Wood decaying fungi will only be ac
- Page 153 and 154: to promote decay prevails. Two of t
- Page 155: Acknowledgements This paper has bee
- Page 158 and 159: (a driving rain gauge), however, is
- Page 160 and 161: Fig. 1. Map of Norwayshowing the lo
- Page 162 and 163: Frequency 25 20 15 10 5 0 highest p
- Page 164 and 165: interesting to compare those result
- Page 167 and 168: Effects of wind exposure on roof sn
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- Page 171 and 172: variety of roofs and wind exposures
- Page 173 and 174: Li and Pomeroy [13] evaluated hourl
- Page 175 and 176: Fig. 5. Exposure coefficients for 3
- Page 177 and 178: meteorological stations are expecte
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- Page 183: References [1] Standards Norway. De
The frost decay exposure index (FDEI) is thus defined as the accumulated annual<br />
average sum of 4-day rainfall prior to days with freezing events. A 4-day spell of rainfall is<br />
shown to provide a reliable basis for climate differentiation of frost decay risk.<br />
A national map of the calculated frost decay exposure indices is presented in Fig. 5,<br />
based on climate records for 168 weather stations in Norway and summing 4-day rainfall<br />
ahead of freezing events.<br />
Fig. 5. Frost decay exposure index (FDEI) map for Norway: relative potential for a climate to accelerate frost<br />
decay or promote frost damage. Weather data for the reference 30-year period 1961 – 1990 is used, summing<br />
4-day rainfall prior to freezing events.<br />
Page 9 of 13
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