Wind Hazard Risk Assessment and Management for Structures

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NEGATIVE WALL PRESSURE (COV = 0.509) POSITIVE WALL PRESSURE (COV = 0.977) Chapter 2. Structural Components and Wind Directionality 36 -60% -60% -40% -40% -20% Percentage Difference -20% Percentage Difference 0% All Records |s| – Rmax < 0 |s| – Rmax ! 0 EXTERNAL PRESSURE AT ROOF NEAR- EDGE NEAR-EDGE ROOF EXTERNAL (COV PRESSURE = 0.093) 0.5 (COV = 0.093) 0% All Records |s| – Rmax < 0 |s| – Rmax ! 0 ROOF CORNER EXTERNAL PRESSURE (COV = 0.200) LEGEND 0.4 -60% -60% 0.3 Category 1 Category 3 0.2 K-S Statistic -40% -40% Category 5 0.1 0 -20% -20% |s| – Rmax ! 0 All Records |s| – Rmax < 0 Percentage Difference Percentage Difference 0% 0% All Records |s| – Rmax < 0 |s| – Rmax ! 0 All Records |s| – Rmax < 0 |s| – Rmax ! 0 Figure 2.9: Percentage differences between the probabilities of failure (Pf ) (obtained from time-stepping method) and the approximated probabilities of failure (P ∗ f ) (obtained from point-in-time method) for lognormally distributed resistances.
Chapter 2. Structural Components and Wind Directionality 37 Overall, all probabilities of failure are underestimated significantly by the point-in-time method due to the underestimation of wind load. The degree of underestimation ranges from about -5% to -60%. In addition, by comparing Figures 2.8 and 2.9, it shows that the choice of probability model for the resistance changes the percentage difference in probability of failure substantially. Unlike the Kolmogorov-Smirnov statistics related to wind pressure, the percentage differences in probability of failure do not exhibit any obvious trend with the variation of the pressure coefficient with respect to wind angle. The relationship between hurricane intensity and the percentage difference in probability of failure also differs for each wind pressure coefficient. However, it is observed that in almost all instances the percentage difference is larger in case the structure is within the radius of maximum wind for some time interval (|s| − Rmax < 0) than when the structure is located outside the radius of maximum wind (|s| − Rmax ≥ 0). 2.5 Discussion The point-in-time method underestimates the wind load primarily because it neglects the effect of changing wind angle during individual wind time series. Maximum wind pressure usually does not occur at maximum wind speed if the pressure coefficient varies significantly with the wind angle or if the change in wind angle is abrupt over time. In the single-limit- state reliability problems, the probabilities of failure are underestimated by up to 60%. If the interdependence among failures of structural components is considered, the point-in- time approach is expected to become even less accurate. For example, in low-rise structures, the breakage of a window, which changes the internal pressure of the structure, would affect the subsequent pressure loading on the envelope components and hence significantly change their failure probabilities. The point-in-time approach cannot capture the subsequent effect of any component’s failure on the other components. In addition, the numerical examples consider wind pressure only. If debris impact is included, the effect of wind directionality
Page 1 and 2: Wind Hazard Risk Assessment and Man
Page 3 and 4: Abstract Rising hurricane damages o
Page 5 and 6: me, has given me countless fun time
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Page 9 and 10: CONTENTS ix 5.3 Hazard model . . .
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LEGEND Roof sheathing onnection ind
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Chapter 4. Integrated Multi-Structu
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DAMAGE ANALYIS USING MAXIMUM WIND V
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Chapter 4. Integrated Multi-Structu
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Chapter 5. Long-Term Risk Assessmen
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(a) Change in Mean Frequency / Year
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(a) Change in Mean Frequency / Year
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simulated. Chapter 5. Long-Term Ris
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Percentage Change in Mean Frequency
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Expected Total Structural Damage Co
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Structural Damage Ratio 1 0.9 0.8 0
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Chapter 6 Conclusions and Future Wo
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Chapter 6. Conclusions and Future W
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Chapter 6. Conclusions and Future W
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Bibliography American Meteorologica
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BIBLIOGRAPHY 131 Federal Emergency
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BIBLIOGRAPHY 133 over the gulf of S
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BIBLIOGRAPHY 135 Lin, N., Vanmarcke
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BIBLIOGRAPHY 137 Rosowsky, D. and C
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BIBLIOGRAPHY 139 Vanmarcke, E., Lin
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Wind Hazard Risk Assessment and Management for Structures

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