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Figure 1. Wind tunnel models: (a) Building with a flat roof (0°); and (b) Building with a gabled roof (45°).

Figure 1 Wind tunnel models: (a) Building with a flat roof (0°); and (b) Building with a gabled roof (45°).

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Table 1. Model dimensions and building heights tested tunnel. The flow approach profiles of mean wind velocity and turbulence intensity measured using a 4-hole Cobra probe (TFT) for the simulated terrain exposure (see Fig. 2). The wind velocity at free stream was 13.6 m/s. The power law index o of the mean wind velocity profile was set at a=0.15. Although it could be argued that it is not com- mon for medium height buildings to be situated in open terrain, this exposure was chosen as a kind of conservatism since higher loads are expected to act on the tested buil- dings in this case. The pressure measurements on the mo- dels were conducted using a system of miniature pressure scanners from Scanivalve (ZOC33/64Px) and the digital service module DSM 3400. A standard tubing system was used in these measurements, in order to minimize the Gain and Phase shifts of pressure signals due to Helmholtz’s resonance effects. Corrections were made by using tradi- tional restrictors. The pressure measurement tubes have an outer and inner diameter of 2.18 and 1.37 mm respectively. The length is 55 cm and restrictors are installed at 30 cm from the location on the building model. All measurements were synchronized with a sampling rate of 300 Hz on each channel for a period of 27 sec (i.e., about one hour in full scale). It is well known that the mean wind speed has the tendency to remain relatively constant over smaller periods of time (i.e., 10 minutes to an hour) assuming stationarity of wind speed, as reported by van der Hoven (1957). This period is also suitable to capture the gust loads, which may be critical for structural design.
Table 1. Model dimensions and building heights tested tunnel. The flow approach profiles of mean wind velocity and turbulence intensity measured using a 4-hole Cobra probe (TFT) for the simulated terrain exposure (see Fig. 2). The wind velocity at free stream was 13.6 m/s. The power law index o of the mean wind velocity profile was set at a=0.15. Although it could be argued that it is not com- mon for medium height buildings to be situated in open terrain, this exposure was chosen as a kind of conservatism since higher loads are expected to act on the tested buil- dings in this case. The pressure measurements on the mo- dels were conducted using a system of miniature pressure scanners from Scanivalve (ZOC33/64Px) and the digital service module DSM 3400. A standard tubing system was used in these measurements, in order to minimize the Gain and Phase shifts of pressure signals due to Helmholtz’s resonance effects. Corrections were made by using tradi- tional restrictors. The pressure measurement tubes have an outer and inner diameter of 2.18 and 1.37 mm respectively. The length is 55 cm and restrictors are installed at 30 cm from the location on the building model. All measurements were synchronized with a sampling rate of 300 Hz on each channel for a period of 27 sec (i.e., about one hour in full scale). It is well known that the mean wind speed has the tendency to remain relatively constant over smaller periods of time (i.e., 10 minutes to an hour) assuming stationarity of wind speed, as reported by van der Hoven (1957). This period is also suitable to capture the gust loads, which may be critical for structural design.
Figure 2. Wind velocity and turbulence intensity profiles for open terrain exposure.
Figure 2. Wind velocity and turbulence intensity profiles for open terrain exposure.
Figure 3. Measurement procedure for horizontal wind forces, Fy and Fy, and torsional moment, M; As already mentioned, the two buildings with 0° and 45° gabled roof angles were tested in open terrain exposure at different eave heights (H = 20, 30, 40, 50 and 60 m) for different wind directions (0° to 90° every 15°). Figure 4(a) presents the variation of maximum torsion coefficient (Cr Mex.) With wind directions for both building configurations and all tested heights. Figures 4(b) and 4(c) show corres- ponding shear ratios from the overall maximum shear orces in X- and Y-directions respectively (i.¢., Cx corr/Cox overalls Csy corr!Cyy overat.)» The maximum torsional coefficient increases significantly (about 2.5 times) with increasing building height from 20 to 60 m. The lowest torsional co- efficient values occur when the wind direction is around 60°. Changing roof angle from 0° to 45° causes an increase of the torsional coefficient by about 50%. As expected, where L = larger horizontal building dimension
Figure 3. Measurement procedure for horizontal wind forces, Fy and Fy, and torsional moment, M; As already mentioned, the two buildings with 0° and 45° gabled roof angles were tested in open terrain exposure at different eave heights (H = 20, 30, 40, 50 and 60 m) for different wind directions (0° to 90° every 15°). Figure 4(a) presents the variation of maximum torsion coefficient (Cr Mex.) With wind directions for both building configurations and all tested heights. Figures 4(b) and 4(c) show corres- ponding shear ratios from the overall maximum shear orces in X- and Y-directions respectively (i.¢., Cx corr/Cox overalls Csy corr!Cyy overat.)» The maximum torsional coefficient increases significantly (about 2.5 times) with increasing building height from 20 to 60 m. The lowest torsional co- efficient values occur when the wind direction is around 60°. Changing roof angle from 0° to 45° causes an increase of the torsional coefficient by about 50%. As expected, where L = larger horizontal building dimension
Figure 4. Torsion load case: (a) maximum torsion coefficient, (b) corresponding shear ratio in X-direction, (c) correspon- ding shear ratio in Y-direction. T. Stathopoulos ef al. | International Journal of High-Rise Buildings
Figure 4. Torsion load case: (a) maximum torsion coefficient, (b) corresponding shear ratio in X-direction, (c) correspon- ding shear ratio in Y-direction. T. Stathopoulos ef al. | International Journal of High-Rise Buildings
Figure 5. Shear load case (transverse direction): (a) maximum shear coefficient in X-direction, (b) corresponding torsion ratio, (c) corresponding shear ratio in Y-direction. Wind Load Combinations Including Torsion for Rectangular Medium-rise Buildings
Figure 5. Shear load case (transverse direction): (a) maximum shear coefficient in X-direction, (b) corresponding torsion ratio, (c) corresponding shear ratio in Y-direction. Wind Load Combinations Including Torsion for Rectangular Medium-rise Buildings
Figure 6. Shear load case (longitudinal direction): (a) maximum shear coefficient in Y-direction, (b) corresponding torsion ratio, (c) corresponding shear ratio in Y-direction. T. Stathopoulos ef al. | International Journal of High-Rise Buildings
Figure 6. Shear load case (longitudinal direction): (a) maximum shear coefficient in Y-direction, (b) corresponding torsion ratio, (c) corresponding shear ratio in Y-direction. T. Stathopoulos ef al. | International Journal of High-Rise Buildings
Figure 7. Torsional coefficient comparison for flat-roofed rectangular buildings with height 60 m located in open country exposure. Wind Load Combinations Including Torsion for Rectangular Medium-rise Buildings
Figure 7. Torsional coefficient comparison for flat-roofed rectangular buildings with height 60 m located in open country exposure. Wind Load Combinations Including Torsion for Rectangular Medium-rise Buildings
Figure 8. Overall shear ratios (Cy, com/Cy max.) at peak torsion for the 60m high flat-roofed building evaluated by Keast et al. (2012) and those from current study.
Figure 8. Overall shear ratios (Cy, com/Cy max.) at peak torsion for the 60m high flat-roofed building evaluated by Keast et al. (2012) and those from current study.
neers Standard (ASCE 7-10), and European Building Code (EN 1991-4-1). figure 7.5 and table 7.1 available in section 7. The non- uniform distribution of wind loads was recognized by applying triangular loading (EN 1991-1-4, 2005).
neers Standard (ASCE 7-10), and European Building Code (EN 1991-4-1). figure 7.5 and table 7.1 available in section 7. The non- uniform distribution of wind loads was recognized by applying triangular loading (EN 1991-1-4, 2005).
Figure 9. Comparison of the torsional load cases specified for medium-rise buildings in NBCC 2010, ASCE 7-10 and EN 1991-1-4.
Figure 9. Comparison of the torsional load cases specified for medium-rise buildings in NBCC 2010, ASCE 7-10 and EN 1991-1-4.
Table 4. Peak torsion and shear force coefficients evaluated from all wind directions flat- and gabled-roof buildings are 0.68, 0.74, see Tables 5 and 6. As indicated in Table 7 the corresponding torsion will be 0.75 (rounded number from 0.74) of the maximum torsion (given in Table 4). Likewise, the torsion load case in the transverse direction was defined by applying the maximum torsion and the corresponding shear forces in X- and Y-directions obtained for wind directions between 0° and 45°. suggested wind load combination factors for designing medium-rise buildings with rectangular plan. Shear and orsion load cases are provided for transverse and longi- tudinal directions, as illustrated in Fig. 12. The shear load case in transverse direction was defined by applying the maximum shear force in X-direction (given in Table 4) with he corresponding torsion and shear in Y-direction. These corresponding values were introduced in a form of ratio from the maximum torsion or shear component and this ratio is the highest obtained from testing the two build- ings in wind direction range 0° to 45°. For instance, the highest corresponding torsion ratio due to winds in trans- verse direction - wind direction range 0° to 45° - for the
Table 4. Peak torsion and shear force coefficients evaluated from all wind directions flat- and gabled-roof buildings are 0.68, 0.74, see Tables 5 and 6. As indicated in Table 7 the corresponding torsion will be 0.75 (rounded number from 0.74) of the maximum torsion (given in Table 4). Likewise, the torsion load case in the transverse direction was defined by applying the maximum torsion and the corresponding shear forces in X- and Y-directions obtained for wind directions between 0° and 45°. suggested wind load combination factors for designing medium-rise buildings with rectangular plan. Shear and orsion load cases are provided for transverse and longi- tudinal directions, as illustrated in Fig. 12. The shear load case in transverse direction was defined by applying the maximum shear force in X-direction (given in Table 4) with he corresponding torsion and shear in Y-direction. These corresponding values were introduced in a form of ratio from the maximum torsion or shear component and this ratio is the highest obtained from testing the two build- ings in wind direction range 0° to 45°. For instance, the highest corresponding torsion ratio due to winds in trans- verse direction - wind direction range 0° to 45° - for the
Figure 10. Comparison of peak shear coefficients (Cy vax, and Cy, vax.) evaluated by wind tunnel, NBCC2010, ASCE7-10, and EN 1991-1-4. T. Stathopoulos ef al. | International Journal of High-Rise Buildings
Figure 10. Comparison of peak shear coefficients (Cy vax, and Cy, vax.) evaluated by wind tunnel, NBCC2010, ASCE7-10, and EN 1991-1-4. T. Stathopoulos ef al. | International Journal of High-Rise Buildings
Figure 11. Comparison of peak torsion coefficient (Cr .,) evaluated by wind tunnel, NBCC2010, ASCE7-10, and EN 1991-1-4.
Figure 11. Comparison of peak torsion coefficient (Cr .,) evaluated by wind tunnel, NBCC2010, ASCE7-10, and EN 1991-1-4.
Table 6. Peak corresponding force component ratios for building with gabled-roof (45°) tested at all heights Table 7. Suggested design load combination factors fot rectangular buildings
Table 6. Peak corresponding force component ratios for building with gabled-roof (45°) tested at all heights Table 7. Suggested design load combination factors fot rectangular buildings
Table 5. Peak corresponding force component ratios for building with flat-roof (0°) tested at all heights
Table 5. Peak corresponding force component ratios for building with flat-roof (0°) tested at all heights
(*These values are the absolute maximum coefficients for each load case. Refer to Tables 4, 5 and 6 for simultaneous and maxi- mum values for the flat- and gable-roofed rectangular buildings.)
(*These values are the absolute maximum coefficients for each load case. Refer to Tables 4, 5 and 6 for simultaneous and maxi- mum values for the flat- and gable-roofed rectangular buildings.)
Naturally, additional experimental work for buildings with different aspect ratios would be useful in order to generalize the current findings.
Naturally, additional experimental work for buildings with different aspect ratios would be useful in order to generalize the current findings.
Figure 12. Suggested shear and torsion wind load cases in transverse and longitudinal directions for rectangular building design.
Figure 12. Suggested shear and torsion wind load cases in transverse and longitudinal directions for rectangular building design.
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