PSI - Issue 64

Mahdi M.K. Zanjani et al. / Procedia Structural Integrity 64 (2024) 1134–1141 Zanjani et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The approximation in Eq. (10) is plotted in Fig. 3 as a continuous line, together with two other dashed lines representing a lower and an upper limit, respectively, as proposed in Eqs. (11) and (12). 3 ' 0.145 c f  = (11) 3 ' 0.195 c f  = (12) In other words, this proposal is based on the hypothesis that for a given density, not a unique value but a range of possible compressive strengths can be in correspondence to the target density, and not due to dispersion but because any change in mix proportion conducts to a different cementitious composite with different physical and mechanical properties (Folino et al., 2009; Folino & Etse, 2011). In summary, a target density can be determined for optimizing the energy performance of a building envelope. Then, regarding structural constraints, a suitable compressive strength in the range delimited by Eqs. (11) and (12) can be specified and matched with the formulation of Eq. (8) and (9). Further experimental data, including the impact of either PCM or MPCM on porosity and strength, will be addressed in subsequent research following this study. 3.3. Computation of the building energy performance The energies and ℋ consumed for cooling and heating, whose sum is the objective function Eq. (6), is determined by using EnergyPlus TM V23.1.0 where the input data file ( idf ) to run BESTEST 900 in E+ can be downloaded from the repository of the U.S. National Renewable Energy Laboratory (NREL). Besides all the building characteristics specified in the idf file, the energy performance of a building is strongly dependent on the local weather. Let us assume the current building located at Bilbao-Spain, with climate Cfb (Temperate oceanic climate) in the Köppen-Geiger classification: i.e., warm summer, mild winter, rain all year, with average temperatures of 19.9 °C and 9.5 °C for typical summer and winter weeks. To define the local weather with the detail needed for E+, we use the typical meteorological year (TMY) at Bilbao airport for the period 2007-2021; the corresponding E+ weather file ( epw ) is downloadable for free from https://climate.onebuilding.org/. The dry bulb temperature for the typical and extreme weeks in winter and summer in Bilbao from this file is shown in Fig. 4.

Fig. 4. Hourly outdoor dry bulb T along extreme summer/winter weeks of Bilbao TMY.

4. Building Energy Performance Simulations For the original BESTEST 900 at Bilbao, chosen as reference, the annual energy consumption for cooling and heating computed by E+, respectively and ℋ , and their sum ℐ is: = 1432.96 kWh, ℋ = 581.87 kWh, ℐ = 2014.83 kWh. (13) On the other hand, for the BESTEST-NRGF 900, the insulation and structural layers of the external wall are replaced with =8 layers of NRG&STRUCT-foams, whose variation will be determined by solving the non-linear continuous optimization problem of Eq. (5) subject to the bound constraints placed in Eq. (7) and the inequality constraints of Eq. (8).