Lisø PhD Dissertation Manuscript - NTNU

More documents

Recommendations

Info

<strong>Lisø</strong>, K.R./ Building envelope performance in harsh climates: Methods for geographically dependent design year period 1961-1990. The proposed climate index is to be justified in the future in relation with building defects observations in different climates. Further development of the index will focus on providing quantitative information on the connection between climatic exposure in different regions and durability of different porous, mineral building materials. This work should also include analyses of the influence of frost period lengths on the assessment of frost damage risk mapping. Field investigations and laboratory testing of different materials are needed for validation and further improvement of the index. An important issue to be addressed is the connection between frost resistance and suction rate, especially of interest for clay bricks. Decay potential in wood structures (Paper X) Climate indices allowing for quantitative assessment of building envelope performance or decay potential may be an important element in the development of adaptation measures to meet the future risks of climate change. Established quantified relations between climatic impact and material behaviour or building envelope performance, can be used as a tool for evaluation of the need for changes in performance requirements or decay rates due to climate change under global warming incorporating data from regional- and local-level climate change scenarios. A national map of the potential for decay in wood structures in Norway, based on Scheffer’s climate index formula, represents an example of a first step towards such measures. Climate data from 115 observing stations for the reference 30-year period 1961-1990 is used. The climate index distribution allows for geographically differentiated guidelines on protective measures. Detailed scenarios for climate change for selected locations in Norway are used to provide an indication of the possible future development of decay rates. The scenario index values clearly points towards a pronounced increase in the potential for decay in wood structures at all locations. In general, climate change scenarios also indicate an increase in the average annual precipitation in Norway during the next 50 years, and thus strengthening this trend. The projected precipitation increase rates are generally smallest in southeastern Norway, and largest along the northwestern and western coast. The quantitative connection between wood decay rates and climatic impact should be further investigated. Field- and laboratory investigations are needed to further improve the reliability of the index for Norwegian climate conditions, including measurements of decay rates in different climates and in different types of wood. Important issues to be considered are the low temperature limit for growth in wood decaying fungi in evidence in Norway, and appurtenant observed growth rates to temperature. 20
<strong>Lisø</strong>, K.R./ Building envelope performance in harsh climates: Methods for geographically dependent design A driving rain exposure index for Norway (Paper XI) Driving rain represents one of the greatest challenges in the design and construction of outer wall structures in Norway. There is, however, no practical tool available for assessing driving rain exposures in the planning and design of the built environment, and there has been little progress made during the past 50 years in the quantification and presentation of driving rain values at weather stations around the country, despite the fact that the nature and quantity of driving rain varies significantly. Weather data at most observing stations in Norway are not recorded as hourly values and are therefore not suitable for existing standardised methods for the determination of driving rain exposure requiring hourly values of rainfall and mean directional wind speed. An alternative method for assessing driving rain exposures based on multi-year records of synoptic observations of present weather, wind speed and direction is therefore developed. Distributions of numbers of rain observations and wind speeds versus wind direction combined with average annual rainfall totals has yielded quantitative information about driving rain exposures at stations, providing a representative picture of the relative frequency of driving rain from different directions. A complete national driving rain map is presented in Figure 3. The principal advantages with the presented method are that the angular distributions of driving rain loads obtained are high resolution in terms of wind direction and that the results are based on long-term series of climate data that are readily available. Where the 1955 driving rain map for Norway yielded driving rain intensities in only four principal directions (north, south, east and west), the new method, with 36 directions, gives a much more detailed picture of the directional dependence of winddriven rain at a weather station. And, driving rain indices presented in this work are from 30 years of synoptic observations representing the most recent climate. The method can also be used to evaluate changes in driving rain loads due to climate change under global warming, through the incorporation of data from climate change scenarios into the methodology. Effects of wind exposure on roof snow loads (Paper XII) International standards do not necessarily reflect national distinctive climate characteristics and topography features. The preparation of national appendices associated with various types of climatic impact is necessary in order for these characteristics to be considered. Again, local climate data needs to be analysed in order to evaluate the validity of proposed methods and tools for assessment and differentiation of climatic loads for various architectural or engineering purposes. In the Norwegian Standard NS 3491-3 “Design of structures – Design Actions – Part 3: Snow loads” from 2001 a new coefficient was introduced, making it possible to take into account the effect of wind exposure on roof snow load. The definition of this exposure coefficient is based on ISO 4355 “Bases for design of structures – Determination of snow loads on roofs”. It is defined as a function of the mean temperature in the coldest winter month and number of days with a wind velocity above 10 m/s. Three winter temperature categories and three winter wind categories are defined, resulting in 9 exposure coefficient values varying from 0.5 to 1.0 21
Page 1 and 2: Building envelope performance asses
Page 3 and 4: Lisø, K.R./ Building envelope perf
Page 29: Lisø, K.R./ Building envelope perf
Page 41 and 42: BUILDING RESEARCH &INFORMATION (200
Page 43 and 44: LisÖ et al. on how to cope with an
Page 45 and 46: LisÖ et al. the exposure to contin
Page 47 and 48: LisÖ et al. business premises. The
Page 49 and 50: LisÖ et al. construction industry
Page 51 and 52: Research in Building Physics, Carme
Page 53 and 54: 4 CLIMATE CHANGE SCENARIOS FOR NORW
Page 55 and 56: with large amounts of precipitation
Page 57 and 58: will most likely be worse, even wit
Page 59: Graves, H.M. & Phillipson, M.C. 200
Page 62 and 63: 766 Nordvik and Lisø The topic of
Page 64 and 65: 768 Nordvik and Lisø into the futu
Page 66 and 67: 770 Nordvik and Lisø climate chang
Page 68 and 69: 772 Nordvik and Lisø 0 Â Â = p d
Page 70 and 71: 774 Nordvik and Lisø probably to a
Page 73 and 74: BUILDING RESEARCH &INFORMATION (200
Page 75 and 76: cost of repairing process-induced b
Page 77 and 78: change in quality (Mehus et al., 20
Page 79 and 80: on the impacts of different climati
Page 81 and 82:
different strategies: risk-based, p
Page 83 and 84:
Lisø, K.R./ Building envelope perf
Page 85 and 86:
Learning from experience - an analy
Page 87 and 88:
An important aspect of the programm
Page 89 and 90:
Concrete walls 32 % LECA masonry 10
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
Page 129 and 130:
climate change is now dominated by
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 142 and 143:
accelerated frost damage or frost d
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
Page 169 and 170:
In ISO 4355 ”Bases for design of
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
Page 179 and 180:
Many of the meteorological stations
Page 181 and 182:
the ground with return period of 30
Page 183:
References [1] Standards Norway. De
show all

Lisø PhD Dissertation Manuscript - NTNU

Create successful ePaper yourself

Delete template?

Save as template?