THANG NGUYEN DAO – JOHN W. VAN DE LINDTTHE UNIVERSITY OF ALABAMA JUNE 20, 2011
PBWE Expectations: Occupant Comfort • Little or no reduction in living/occupant comfort. • Almost a durability issue; no damage or water entry limited to moisture, i.e. no pooling. Continued Occupancy • Up to moderate reduction in comfort but no threat to safety or injury. Electrical, plumbing, and egress still present. • Loss of first gable or roof sheathing panel.
PBWE Expectations: Life Safety • Safety normally provided is not presented • Roof truss-to-wall connection failure; supporting column/post failure Structural Integrity • Visible signs of structural distress, i.e. permanent deformation, structure not safe • Collapse of roof; loss of lateral capacity
PBWE Expectations (Continued): Manageable Loss • Cost to repair structure is below a selected percentage of reconstruction/replacement value. This is dependent on numerous factors, and is often the result of rainwater intrusion and structural failure. • Loss distribution based on the assembly of damageable components.
Example of various levels of building performance as afunction of Hazard Level.
Construction of fragilities for windborne debrisimpact to window: Panel initial position Roof-sheathing trajectories during a hurricane hour Target window Roof-sheathing trajectories that hit the windows during a hurricane hour
Structural loss: Structural components or assemblies are defined as parts of building that resist wind load, or carry dead load and live load during a hurricane.Non-structural loss: The non-structural or content loss is often due to rain water intrusion.
STRUCTURAL PROPERTIES HURRICANE PROPERTIES Non-linear Wind loadstructural analysis statistics Statistics of Wind drivenstructural capacity rain Windborne debris Structural impact risk analysis (not Rainwater included for singlecomponent fragility intrusion house)Structural damage Non-structural component states damage states COST DISTRIBUTIONS GIVEN DAMAGE STATESStructural loss Non-structural loss TOTAL LOSS
Structural loss Wall Missile structureDamage Damage Roof sheathing Roof truss impacts on (Max state description panels members C windows drift/height 1 Damage State D1 P(C|D1) in walls) 1, No damage or very All rooms in 1| 1 No No Negligible minor damage damage level 1 At least one room One One truss C 2 > 0.1 % and 2 Minor damage reach damage window member 2| Damage State D2 P(C|D2) 0.5 % 2, level 2 failure failure > one and Hurricane At least one room > one and properties the > 0.5 % and 3 Moderate damage reach damage the larger of larger of 1% … level 3 5% and 3 20% and 3 > the larger of At least one room > the larger | C 20% and 3 > 1 % and 4 Severe damage reach damage of 5% and 3 Damage State Dn P(C|Dn) and the 3% , level 4 and 20% larger of 50% and 6 At least one room > the 5 Destruction reach damage larger of > 20% >3% level 5 50% and 6Structural damage state for Residential Construction Classes (revised from Vickery et al., 2006) | | . |
Example on PBWE with different expectations Load Coefficient Distribution Mean Source Type of variation Type Lee & Dead 3.5 psf 0.10 Normal Rosowsky load (168N/m2) (2004) Wind Ellingwood 0.8Wn1 0.35 Normal load (1999) Structure Distribution Mean COV Source 40ftx60ftx12ft Resistance Type Finite Element 69 psf Panel Model, Dao and (3.17 0.24 Log Normal capacity van de Lindt kN/m2) (2008) 1,312 lbs Ellingwood et al H2.5 clip 0.10 Normal (5.84 kN) (2004)
Method can be used for PBWE of wood-framestructureThe framework is felt to be a viable design alternative,provided details are worked out, i.e. calibration.During this research many assumptions was made, butthe result still presents a good level of accuracy whenqualitative comparison to hurricane Katrina is made.