make summary for each lucture

HURRICANE MITIGATION 4. Better design and secure roof top equipment and PV systems

WOW test results on Roof Top Equipment Loading are in FBC

12-FAN WOW PHOTOVOLTAIC (PV) TESTING  Dynamic Effects of Wind Loading on Photovoltaic Systems

• Develop more realistic criteria for wind induced vibration of roof mounted PV systems including those installed on non-structural roofs using c-clips.

• Testing on full-scale PV systems indicated that significant wind-induced vibration may occur in systems with much higher natural frequency (~13Hz) than the ≤1 Hz criterion indicted in the ASCE 7 for categorizing dynamically wind sensitive structures. Thus the current ASCE 7 criterion related to dynamic amplification, originally developed with buildings in mind, is not really applicable to judge the dynamic sensitivity of smaller structures, such as PV systems. Additional research is underway using the more powerful 12-fan Wall of Wind to develop a more appropriate criterion to address vibration of small structures. [Moravej et al., ICWE 14]

 Use hurricane straps for roof-to-wall connections to connect the tie beam(s) to each roof truss (stronger than hurricane clips)

• Experiments revealed several failure modes under uplift load, including nails pulling out of the rafter and rupturing of the top plate, rupturing of the rafter, deformation of the hurricane clip, and tearing of the hurricane clip.

HURRICANE MITIGATION 5. Strengthen inter-component connections

HURRICANE MITIGATION • The allowable load capacity of the connection joint with two fasteners is

considerably less than twice the allowable load capacity of the connection joint with one fastener, as is currently indicated in the product manufacturers’ literature.

HURRICANE MITIGATION • Uplift capacities of commonly used roof-to-wall connectors (i.e., hurricane clips)

could be significantly reduced under triaxial load testing as compared with capacities estimated under uniaxial load testing. Such reduction could be as high as about 50% during the presence of high lateral load effects.

• The presence of dominant openings in the windward direction can cause high increase of load on roof-to-wall connections by increasing the internal pressure. Such increase can occur due to breach in the building-envelope causing a dominant windward opening.

 Provide ‘continuous load path’ from roof to wall, wall to wall, wall to foundation to prevent failure at the weak links -- Tie it all together

• Connect the roof to the tie beams with hurricane straps (look for metal hurricane straps in the attic looping over every truss – if missing, then retrofit using more straps) – straps can often be added to wood homes after the home is built; its more difficult to add straps to cement block houses with concrete tie beams.

• Connect the tie beams to vertical cement-filled columns containing steel rods.

• Connect the columns to the foundation.

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 Gluing the roof -- spray a foam glue on the inside of the roof to connect the rafters to the sheathing

• Wind-Uplift Capacity of Residential Wood Roof-Sheathing Panels Retrofitted with Insulating Foam Adhesive (Datin et al., J. Arch. Eng., Vol. 17, No. 4, 2011, pp. 144-154): In hurricane- prone areas, structural retrofits of light-framed wood roof structures are needed to mitigate wind damage to existing residential roof structures because the majority of these have inadequate design strength to resist hurricane-force winds. The results showed that closed- cell sprayed polyurethane foam (ccSPF) adhesive retrofits increase the wind-uplift capacity of the pre-1994 code-minimum wood roof panels by as much as 250–300%. This finding is important because it could provide a means to improve the wind resistance of these older roof designs, which may still account for more than 60% of the existing residential inventory.

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 Concrete roof can be used to reduce risk of roof damage, however, it is more costly. A new product is being at FIU – Supertile. Solid concrete walls are much stronger than concrete block walls.

 A new product in form of a ‘net’ can be draped over the roof and anchored to the ground to help strengthen weak roof systems.

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 Reinforce wooden gables (they can blow in under high winds) • Use bracing to connect the gable end to truss system (concrete block houses can also have

wooden gables)

• The trusses should their own internal bracing structure and not just rely on the roof sheathing to keep them vertical

• Cover gable end vents with shutters or plywood

https://www.youtube.com/watch?v=8Ffg8HFKORY 5 Things to Protect Your Home

https://www.youtube.com/watch?v=SrYL2ooCOxA IBHS Guide to Gable End Bracing

HURRICANE MITIGATION 6. Strengthen gable ends

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• The Florida Building Commission (FBC) has provisions to provide prescriptive solutions for retrofitting gable ends of existing buildings. The prescriptive solutions are designed to strengthen gable ends in existing buildings by bracing the gable-end trusses at 24 inch on center. The retrofits are designed to provide economical, simple, and practical solutions to reduce the vulnerabilities of gable ends to Category 3 and stronger hurricanes.

HURRICANE MITIGATION 7. Reduce Wind-Driven-Rain (WDR) intrusion  Use ridge vents along edge of the roof to ventilate attic space

(preferable to turbine vents that require multiple holes in the sheathing). Ridge vents can keep the rain out as well.

 For turbine vents, use the cap on top before a hurricane.  Improved soffit design: If the fascia board extends below the

underside of soffit, water is less likely to be blown up into eaves  Provide heavy duty underlayment under shingles or tiles -- SWB  Use circular or tubular skylights that are aerodynamically favorable

HURRICANE MITIGATION  Seal roof deck joints using tapes (IBHS Study) • IBHS study demonstrated the value of sealing the roof deck and provided information on the

relative importance of water entry through vents compared to the roof. Water entry tests for the sealed and unsealed roof decks were conducted after shingles were removed. Water entry through the un-taped roof deck joints exceeded that through taped deck and vents.

HURRICANE MITIGATION  Use rain screens (pressure equalization principle)

When the outside air pressure is transferred to an air space behind the exterior cladding, the cladding is exposed to a near-zero pressure differential, i.e., a complete elimination of the driving force for pressure-induced water penetration.

6-FAN WOW STUDY ON VENTS

• Water intrusion increased with higher positive differential pressure across the vent.

• Vent mechanism also affected water intrusion amount for different wind angles of attack.

6-FAN WOW STUDY ON VENTS • Gooseneck vents may allow substantial water intrusion and should have their frontal

opening covered before hurricane events.

• The rotating top portions of turbine vents could be redesigned to close the openings before windstorms strike.

• Louvers of gable end vents could be redesigned to reduce wind-driven rain under oblique wind angles of attack.

• Ridge vents could be protected for wind-driven rain perpendicular to their openings by having a closure mechanism.

• Active/passive controls could also be designed to close various vents automatically as differential pressure increases with the wind speed and wind angle of attack.

HURRICANE MITIGATION 8. Reduce surge and flood damage

 Coastal wetlands may provide critical protection against incoming hurricane storm surges. A 2012 study by Sheng et al. found that "a sufficiently wide and tall vegetation canopy reduces inundation on land by 5 to 40 percent", depending upon the type of storm. The traditional rule of thumb: each 2.7 miles of marsh knocks down the storm surge by 1 foot.

HURRICANE MITIGATION  A flood barrier, surge barrier or storm surge barrier is a specific

type of floodgate, designed to prevent a storm surge from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls, levees (also known as dikes), and other constructions and natural geographical features. Flood barrier may also refer to barriers placed around or at individual buildings to keep floodwaters from entering those buildings.

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HURRICANE MITIGATION  Properly Elevate Your Building

• Learn what your property’s base flood elevation (BFE) is from your local building department and check your property survey to find the elevation of the lowest floor.

• If this floor is not built above the BFE, consider elevating your building. If that is not possible, relocate utilities and valuable belongings at least one foot -to-three foot above your property’s BFE to reduce damage from flooding.

• Any enclosed areas below the BFE (and preferably three feet above the BFE) should have break-away walls, and all utilities and equipment should be located well above the BFE.

HURRICANE MITIGATION  Opt for a major retrofit [FLASH's home safety program suggests

three options]:

• Raise your home on piers or columns so that the lowest floor is above the flood level. This is an expensive option.

• "Wet-proof" your home by installing foundation vents that would allow water to flow through the building, instead of rising inside and causing more damage. You'd need at least two vents on different walls. A 1,000-square-foot house would require 7 square feet of flood vents, according to FLASH.

• Do some "dry proofing" by applying coatings and other sealing materials to your walls to keep out floods.

http://www.floridadisaster.org/mitigation/rcmp/strengthen/strengthen.html

http://www.blueprintforsafety.org/

http://ww5.mysafefloridahome.com/

https://disastersafety.org/fortified/ or https://disastersafety.org/fortified/fortified-home/

https://disastersafety.org/ibhs-news-releases/ibhs-offers-five-recommendations- hurricane-home-protection-2/

[IBHS Offers Five Recommendations for Hurricane Home Protection)

HURRICANE MITIGATION WEBSITES