Reliability of Existing Climate Indices in Assessing the Freeze-Thaw Damage Risk of Internally Insulated Masonry Walls

Abstract

This paper evaluates the reliability of the currently used climate-based indices in selecting a moisture reference year (MRY) for the freeze-thaw (FT) damage risk assessment of internally insulated solid brick walls. The evaluation methodology compares the ranking of the years determined by the climate-based indices and response-based indices from simulations, regarded as actual performance. The hygrothermal response of an old brick masonry wall assembly, before and after retrofit, was investigated in two Canadian cities under historical and projected future climates. Results indicated that climate-based indices failed to represent the actual performance. However, among the response-based indices, the freeze-thaw damage risk index (FTDR) showed a better correlation with the climate-based indices. Additionally, results indicated a better correlation between the climatic index (CI), the moisture index (MI), and FTDR in Ottawa; however, in Vancouver, a better fit was found between MI and FTDR. Moreover, the risk of freeze-thaw increased considerably after interior insulation was added under both historical and projected future climates. The risk of FT damage would increase for Ottawa but decrease for Vancouver under a warming climate projected in the future, based on the climate scenario used in this study. Further research is needed to develop a more reliable method for the ranking and the selection of MRYs on the basis of climate-based indices that is suitable for freeze-thaw damage risk assessment.

Frost Damage Risk in Insulated Masonry Walls: Challenges in Analysing Large Number of Numerical Simulations

“…Since a large part of the literature refers to IFTC, and given their high correlation, it should be preferred over TOF, AFW and MWI. The choice between IFTC and FTDR would deserve deeper investigation since the correlation between these two indicators was found the weakest and even weaker correlations are found in the literature [3], [13]. The discrepancy existing between this study and the literature strengthens the need for additional investigation before establishing guidelines and suggestion in the choice between IFTC and FTDR as frost damage indicator.…”

Potential of frost damage of off-ground foundation stones in Norwegian Stave Churches since 1950 using land surface temperature

“…Then other complex climate-based indices that combine several climatological parameters exist. They are all reported in Sahyoun, et al [25] , and were originally modeled by: ASHRAE [26] i.e., the semi-empirical Wind-Driven Rain Model that uses rainfall, and wind velocity Cornick et al 2003 [27] , i.e., the Moisture Index calculated as a function of hourly values of wetness (WI h ) and dryness (DI h ) indices. Zhou et al 2016 [28] , i.e., the Climatic Index (CI) calculated as a ratio between annual wetting (i.e., the annual WDR) and drying components (i.e., the annual potential evaporation) Salonvaara et al 2010 [29] , i.e., the Severity Index a regression equation developed based on hygrothermal simulations which correlates climatic parameters (e.g., solar radiation, cloud index, wind-driven rain, vapor pressure) with RHT as the performance indicator.…”

“… Zhu et al 2022 [30] (2) Sdr: interfacial expansion area ratio of concrete surface; N: number of FT cycles. Uranjek et al 2021 [31] (3) DI: probabilistic damage index of masonry brick wallet; μ : the ductility of damaged (at n F/T cycles) samples; μ 0 : the ductility of intact (unconditioned at 0 F/T cycles) samples Sahyoun et al 2021 [25] (4) MWI: Modified winter index calculates the level of severity where the MC is higher than the critical level T L : critical value of temperature T i :hourly values of temperature at the investigation point w i : hourly values of moisture content at the investigation point w L : critical value of moisture content Sahyoun et al 2021 [25] (5) FTDR: F-T damage risk index S Ice , Max : Max saturation degree of ice content S Ice , Min : Min saturation degree of ice content Ghobadi et al 2016 [32] ; Mutluturk et al 2004 [33] I N = I 0 e − λN (6) I N : integrity of the tuff after N cycles I 0 : original integrity of the tuff λ : decay constant N: cycle of F-T Grossi et al 2007 [19] (7) F: Surface Frost Index DDF: seasonal degree-days sums above 0 °C DDT: seasonal degree-days sums below 0 °C …”

“…– Sahyoun et al 2021 [25] reported two indices: the modified winter index and the F-T damage risk index, the first (eq. (4)) utilizes hourly values of MC to calculate the level of severity where the MC is higher than the critical level, the freezing is assumed to occur at 0 °C within the material; while the second (eq.…”

“…To overcome this limitation, several algorithms much more complex have been proposed with climate-based input parameters or with a mix of climate and material response-based parameters. In the first case, they require several climatic data [26] , [28] obtained by weather stations or by using hygrothermal building simulations [29] , and semiempirical models [27] ; in the second case they demand long and costly surveys to gain experimental data to assess the integrity of the material in terms of indexes as damage [2] or integrity [32] value, probabilistic [31] , modified winter, surface frost, and F-T [25] damage risk indices or interfacial expansion area ratio [30] . In this study an effort is done to simplify the algorithm without losing in results reliability.…”