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Tropical Storms and Hurricanes. Updated 2008. Tropical Storms and Hurricanes. Introduction Tropical storms and Hurricanes are formed from tropical disturbances that travel across the Atlantic ocean toward the U.S. coast line.

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tropical storms and hurricanes2
Tropical Storms and Hurricanes

Introduction

  • Tropical storms and Hurricanes are formed from tropical disturbances that travel across the Atlantic ocean toward the U.S. coast line.
  • In 2004, Hurricanes and tropical storms were responsible for an estimated $50 billion dollars in damage. Five Hurricanes made landfall in the state of Florida. Three of them had at least 115 mph sustained winds.
  • In 2005, the Atlantic Hurricane season was the most active season in recorded history. The impact of the season was widespread and ruinous with at least 2,280 deaths and record damages of over $128 billion USD.
tropical storms and hurricanes how hurricanes form
Tropical Storms and HurricanesHow Hurricanes Form
  • Tropical Disturbance: An area of organized convection, originating in the tropics that maintains its identify for 24 hours or more. It is often the first developmental stage of any tropical depression, tropical storm or hurricane.
  • Tropical Storm: A severe storm that develops offshore over tropical seas. When wind speeds reach 39 mph, the tropical disturbance becomes a tropical storm and is given an official name.
  • Hurricane: When a tropical storm takes a cyclonic form and has reached a constant wind speed of 74 mph or more. The eye of the storm is usually 20 – 30 miles wide and can extend over 400 miles. Strong hurricane windows can inflict moderate to severe damage to buildings and may cause flooding in coastal areas.
tropical storms and hurricanes saffir simpson scale
Tropical Storms and HurricanesSaffir – Simpson Scale
  • The Saffir – Simpson Hurricane scale
  • is a Category 1 to Category 5 rating
  • based on the hurricane’s present
  • intensity.
  • The scale is used to give an estimate of
  • potential property damage and flooding
  • expected along the coast.
  • Wind speed is the determining factor in
  • the scale, as storm surge values are highly
  • dependent on the shape of the coastline.
tropical storms and hurricanes property damage
Tropical Storms and HurricanesProperty Damage
  • Flying debris is a major concern, but

research has shown that most destructive

damage occurs when the building envelope

is breached.

  • A breach of only 10% of the building envelope,

due to a broken window, can destroy a structure.

  • The increased wind pressure on the anchoring of the roof to the walls and the walls to the floor is typically what leads to building failure.
tropical storms and hurricanes property damage continued
Tropical Storms and HurricanesProperty Damage Continued..
  • Theory Of Destruction
  • Debris penetrates the building
  • envelope.
  • Negative pressure builds up from
  • the inside
  • Roof lifts off allowing water to enter
  • When a window is shattered or
  • blown out, the building becomes
  • partially enclosed and as a result,
  • wind pressure on the roof and walls
  • is significantly increased.
tropical storms and hurricanes storm activity in 2005
Tropical Storms and HurricanesStorm Activity in 2005
  • 2005 was the most active hurricane storm
  • season in recorded history.
  • The impact was widespread and ruinous
  • with over 2,000 deaths and record
  • damages of over $128 billion dollars.
  • A record twenty-eight tropical and sub-
  • tropical storms formed, of which fifteen
  • became hurricanes.
  • Five became Category 4 hurricanes and
  • four reached Category 5 strength.
tropical storms and hurricanes storm activity in 2006 2007
Tropical Storms and HurricanesStorm Activity in 2006 & 2007
  • 2006 was a fairly inactive storm season.

It was unusual that no hurricanes

made U.S. landfall.

  • 2007 marked an earlier beginning to a fairly active season when Subtropical Storm Andrea formed on May 9, 2007 and Tropical Storm Olga developed on December 11th.
  • 2007 was fairly active with 15 named storms, though their intensities did not meet predictions.
building codes and wind loads introduction
Building Codes and Wind LoadsIntroduction
  • When Hurricane Andrew hit Florida in
  • August of 1992, causing an estimated $25
  • billion dollars in damages, it became the
  • “wake up call” for the construction industry.
  • Andrew revealed wind zones were
  • understated, existing standards were not
  • being adhered to and codes were not being
  • enforced.
  • As a result, demands for missile impact tests,
  • standards and building codes have been put in
  • place and are subject to stringent enforcement.
building codes and wind loads impact of hurricane andrew
Building Codes and Wind LoadsImpact of Hurricane Andrew

As a result of Hurricane Andrew, codes

and standards were revised to require:

  • Higher Wind Loading: Coastal wind load

charts were redefined significantly higher.

  • Effective March 8, 2007, Panhandle is no

longer exempt from the wind-borne debris

region.

  • Negative Pressures: Building components

required to withstand high wind loads, greatest impact realized from negative pressure loads.

  • Impact and Cyclic Testing: Cladding and building components must be tested and certified for compliance.
building codes and wind loads code expansion
Building Codes and Wind LoadsCode Expansion
  • Codes originally developed for Florida have
  • expanded from Texas, along the Gulf and
  • up through the Atlantic seaboard to Maine.
  • This map shows wind speeds for areas
  • along the southeastern coast and where
  • codes are in place.
  • The contour lines on this map are wind
  • speed lines, not design pressures. Wind
  • speeds are converted to design pressures
  • using ASCE-7 (American Society of Civil
  • Engineers).

Source: Institute of Business and Home Safety

building codes and wind loads current building codes
Building Codes and Wind LoadsCurrent Building Codes
  • Most building codes used in the United States are based on the International Building Code (IBC), www.iccsafe.org which references the American Society

of Civil Engineers (ASCE), www.asce.org, standard ASCE-7 “Minimum Design Loads for Buildings and Other Structures” for wind load design.

  • Even those jurisdictions that have their own statewide building code, such as Florida, Texas, and North Carolina, typically reference the same wind load provisions as those found in the IBC (with some local amendments).
  • For instance, in Florida, Miami Dade and Broward counties require buildings to utilize tested and approved windborne debris protection systems, such as shutters or impact windows.
building codes and wind loads asce 7 development

Standard Development

ASCE 7 – 88 110 MPH Maximum

ASCE 7 – 93 ANSI 58.1 Integration

ASCE 7 – 95 150 MPH Maximum

ASCE 7 – 98 150 MPH Maximum

ASCE 7 – 02 Current Standard

incorporated IBC

provisions

Building Codes and Wind LoadsASCE 7 Development
  • ASCE - 7 outlines basic wind load provisions and

procedures to convert basic wind speed into

design pressures based on several variables.

  • The wind load provisions of ASCE - 7 have

developed over the years.

The most current versions is ASCE 7 – 05.

  • Section 6 of ASCE – 7 deals with wind load

calculations for “Main Wind-Force Resisting

Systems” and “Components and Cladding”

building codes and wind loads terminology
Building Codes and Wind LoadsTerminology
  • Design Load: Also referred to as design pressure (DP), design load is in the air pressure that a window system must be able to withstand as determined by the project architect in accordance with applicable codes. Design loads are usually expressed in both positive and negative pounds per square foot (PSF).
  • Wind Load: Also referred to as wind pressure, wind load is the amount of pressure exerted by the wind on a window system. Wind loads are generally expressed in pounds per square foot (PSF) and are not to be confused with basic wind speed, which is usually expressed in miles per hour (MPH).
building codes and wind loads terminology cont d
Building Codes and Wind LoadsTerminology Cont’d…
  • End Zone: The end zone consist of the area within 10% of the shortest building dimension to the edge of the structure. End zones are essentially the corners of a structure and typically require higher design pressures.
  • Interior Zone: The interior zone consists of the area between the end zones. Interior zones typically require lower design pressures than end zones.
  • Opening Area: Opening area refers to the size of the window opening and is used to determine design pressures as per ASCE – 05. Large openings typically have lower design pressures than smaller openings.
  • Weighted Area: When an opening falls partially within an end zone, the total window area is averaged based on the square footage located in each zone.
building codes and wind loads which code applies
Building Codes and Wind LoadsWhich code applies?

State

Georgia

North

Carolina

South

Carolina

Florida

Texas

Alabama

SBCCI

IBC

County

County ?

IBC

NCBC

IBC

Texas Department

Of Insurance for

Coastal Counties

No Hurricane

Code for Other

Counties

Florida Building

Code (FBC) for

Other Counties

Local Building

Code for Dade

And Broward

building codes and wind loads who approves impact products
Building Codes and Wind LoadsWho Approves Impact Products?

There are three major product approval

Agencies for impact resistant glazing:

  • Texas Department of Insurance

www.tdi.state.tx.us

  • Florida Building Commission

www.dca.state.fl.us/fbc

  • Miami – Dade Product Approval

www.buildingcoeonline.com

These web sites provide information on

Approved impact glazing products.

building codes and wind loads who conducts inspections
Building Codes and Wind LoadsWho Conducts Inspections?
  • For standard applications, inspections

are conducted by the local building

department, as legislated by the County

Code Compliance Office.

  • Special Inspectors or Consulting Engineers

may be brought in to inspect non-standard

applications.

  • FEMA projects are typically inspected by

Special Inspectors, while schools are

typically subject to inspection by local

and state building inspectors.

building codes and wind loads what s really required
Building Codes and Wind LoadsWhat’s Really Required?
  • Design Pressure Ratings: Elevation drawings should indicate design pressure ratings for the structure, including end zone and interior zone pressures as determined by the engineer of record in accordance with ASCE - 7.
  • Building Exposure: Listing of Building Exposure as defined by ASCE - 7. Structures in urban, suburban, or wooded areas are typically Exposure B, while structure in open fields or on coast lines are typically Exposure C.
  • Basic Wind Speed: Basic Wind Speed for the site represented in MPH. This is based on the 50-year average of the peak wind speed at a given height and exposure (typically 33’ for Exposure C) averaged over three seconds.
building codes and wind loads what s really required20
Building Codes and Wind LoadsWhat’s really Required?
  • Importance Factor: A safety factor related to the degree of hazard to human life and property. Various “essential use” facilities, such as hospitals, have an importance factor of 1.15, as compared to residential construction (1.00).
  • Site Specific Shop Drawings: All submissions should include supporting site specific shop drawings for all fenestration products, fenestration components and exterior cladding.
  • Notices of Acceptance: Submissions should also include individual product Notices of Acceptance (NOA’s) or product approvals as issued by the governing code compliance office from each participating trade.
building codes and wind loads summary
Building Codes and Wind LoadsSummary

The codes and standards implemented in

Response to Hurricane Andrew resulted in:

  • Higher wind load provisions and

higher structural loading

  • Large and small missile impact

testing and cyclic testing

  • Improved code reinforcement at the

local, regional and state levels

Today’s standards help provide increased

Protection for hurricane-prone areas.

wind load testing introduction

Building heights > 30’ – Small Missing Testing

Wind Load TestingIntroduction
  • The IBC requires fenestration in

coastal areas to be AAMA certified,

which requires windows to undergo

structural, impact and cyclic testing.

  • Small and large missile impact testing

helps stimulate the ability of a window

to resist hurricane driven debris.

  • Cyclic testing is performed after impact

testing and is designed to simulate positive

and negative pressures of hurricane-force

winds.

window load testing test standards
Window Load TestingTest Standards
  • The standard test method for cyclic testing referenced by the IBC and AAMA, is ASTM E1886-05 “Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors and Impact Protective Systems Impacted by Missile (s) and Exposed to Cyclic Pressure Differentials”.
  • Small and large missile impact testing is covered by ASTM E1996-04 “Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors and Impact Protective Systems Impacted by Windborne Debris in Hurricanes”
  • Equivalent Miami-Dade and Broward standards are TAS 201-94 “Impact Test Procedure”, TAS 202-94 “Criteria for Testing Impact and Non Impact Resistant Building Envelope Components Using Uniform Static Air Pressure”, and TAS 203-94 “Criteria for Testing Products Subject to Cyclic Wind Pressure Loading”.
wind load testing large missile
Wind Load TestingLarge Missile
  • Impact testing is performed on
  • windows to simulate the ability of
  • the frame and glazing material to
  • resist hurricane-driven debris.
  • Large missile testing is an 8’ long, 9lb,
  • 2x4 board shot twice at a window
  • at a speed of 50’ feet per second.
  • Window products that are large missile
  • tested are typically used on elevations
  • from ground up to 30’ or close to a debris
  • generation point.
wind load testing small missile

Building heights > 30’

Wind Load TestingSmall Missile
  • Small missile testing involves 2 gram

steel balls (to represent roof rock)

shot at the window twice product at a

speed of 130’ per second.

  • Windows that are small missile

tested are typically used on

elevations at heights over 30’.

  • Window products that are large missile

tested can also be used at heights over

30’, however they are typically more

expensive.

wind load testing cyclic testing
Wind Load TestingCyclic Testing
  • Following missile testing, products are
  • subjected to cyclic testing designed to
  • simulate the positive and negative
  • pressures of hurricane-force winds.
  • Windows are subjected to 9,000 cycles
  • of positive (inward-acting) and negative
  • (outward-acting) pressures.
  • These positive and negative pressures
  • are related to the design pressure and are
  • applied in a prescribed sequence in cycles
  • lasting 1 to 3 seconds.
wind load testing cyclic testing cont d

Sequence Pressure Cycles

Sequence Pressure Cycles

Positive 0.2 DP – 0.5 DP 3,500

Positive 0.0 DP – 0.6 DP 300

Positive 0.5 DP – 0.8 DP 400

Positive 0.3 DP – 1.0 DP 100

Negative 0.3 DP – 1.0 DP 50

Negative 0.5 DP – 0.8 DP 1,050

Negative 0.0 DP – 0.6 DP 50

Negative 0.2 DP – 0.5 DP 3,350

Positive 0.2 DP – 0.5 DP 3,500

Positive 0.0 DP – 0.6 DP 300

Positive 0.5 DP – 0.8 DP 400

Positive 0.3 DP – 1.0 DP 100

Negative 0.3 DP – 1.0 DP 50

Negative 0.5 DP – 0.8 DP 1,050

Negative 0.0 DP – 0.6 DP 50

Negative 0.2 DP – 0.5 DP 3,350

Wind Load TestingCyclic Testing Cont’d…..
  • For example, given a design pressure

of 100 psf, the sample would first be

subjected to positive pressures from

20 psf to 50 psf for 3,500 cycles.

  • Most failures occur when the sample

is subjected to positive pressures from

0.4 DP to 1.0 DP for 100 cycles.

  • Test samples are deemed to have

passed cyclic testing if no openings

larger than 3” in diameter, or tears

or cracks longer than 5” appear.

building outside the box introduction
Building Outside the BoxIntroduction
  • In some situations, the standard

procedures for specifying windows

that meet current building code

requirements may not apply.

  • For instance, what if a particular

window product has not been

tested in the size required for the

project?

  • What if the product does not have a

NOA? What if the wind loads are

unusually high? What about mid-rise

and high – raise challenges?

building outside the box project specific testing
Building Outside the BoxProject Specific Testing
  • For projects that require unique

configurations of glazing that have

not been tested, it is possible to

conduct project specific testing.

  • In these instances, large mock ups

must be constructed in order to

undergo impact and cycle testing.

  • Project specific testing can be costly

and time consuming. As a result, it

is important to plan design criteria

early and involve manufacturers.

building outside the box wind tunnel testing
Building Outside the BoxWind Tunnel Testing
  • In addition to project specific testing,

wind tunnel testing is an acceptable

alternative to straight line, deductive

calculations.

  • For structures with high design pressures,

wind tunnel testing can reduce design

pressures by 30%

  • Reduced loading can significantly lighten

the structural performance requirements

of the window and save thousands in

material costs.

building outside the box comparative analysis vs rational analysis
Building Outside the BoxComparative Analysis vs. Rational Analysis

Engineering analysis can be used to quality unique window openings, however it is

Important to distinguish between comparative analysis and rational analysis:

  • Comparative Analysis: Comparative analysis uses actual test criteria as a

basis for the evaluation of a product. There are allowable spans that can be

used as a known value when sizing varies. Comparative analysis is commonly

used when project requirements exceed current test sizes.

  • Rational Analysis: Rational analysis is not based on test criteria and essentially

consists of an engineer’s opinion regarding a particular product. Although it

can be based on logical or calculated deductions, it is not recognized by most

certifying entities as an acceptable method for analyzing impact products.

building outside the box points to remember
Building Outside the BoxPoints to Remember
  • If you plan to test, keep in mind that the largest known job size component should be tested along with any accessories that will be used with the system. Multiple or triple arrangements for fenestration products, including mullions, are extremely important. This is often overlooked!
  • It is often thought that rational analysis can be used to compensate for any testing insufficiencies, however this assumption is incorrect. Rational analysis

is not permitted for impact products.

  • Testing involves significant material costs, engineering costs, laboratory costs,

and certification fees. Moreover, lead times for testing and certification often

collide with critical paths. Retesting and remedial repairs, if necessary can

create unexpected delays. In some cases, product approvals can take up to

one year.

windborne debris protection system introduction
Windborne Debris Protection SystemIntroduction
  • In Florida, both Miami-Dade and

Broward counties require buildings

to incorporate tested and approved

windborne debris protection systems

  • These debris protection systems may

consist of protective shutter systems

or impact resistant window systems.

  • Impact resistant glazing is able to resist

wind pressures and often provides better

protection than shutter systems.

windborne debris protection systems protective shutter systems
Windborne Debris Protection SystemsProtective Shutter Systems

Manufacturers offer several different

Types of protective shutter systems:

  • Corrugated Panels
  • Plywood Panels
  • Polypropylene Panels
  • Polycarbonate Panels
  • Accordion Panels

Ease of installation and operation are

Both important factors to consider.

windborne debris protection systems protective shutter systems cont d
Windborne Debris Protection SystemsProtective Shutter Systems Cont’d…..

Protective Shutter Systems Cont’d…

Protective shutter systems have several

Drawbacks compared to impact glazing:

  • Most shutter systems are difficult to

install and labor intensive to operate

  • Permanent shutter systems are highly

invasive and require maintenance

  • Temporary shutter systems tend to be

bulky and can be difficult to store

In addition, shutter systems are typically not

Practical for multi-story applications

windborne debris protection systems impact resistant glazing
Windborne Debris Protection SystemsImpact Resistant Glazing
  • Impact resistant glazing systems are specifically designed to meet strict building codes and the toughest coastal weather challenges.
  • Impact glazing provides 24 hour

protection that offers maximum

protection with minimum effort.

  • Impact resistant glazing products

offer high design pressure ratings

and are tested to withstand the most

severe hurricane-force wind loads.

windborne debris protection systems impact resistant glazing cont d
Windborne Debris Protection SystemsImpact Resistant Glazing Cont’d……

Impact resistant glazing offers several

Advantages over protective shutters:

  • Impact glazing is a practical solution

for both new or retrofit construction

  • Impact glazing offers 24 hour protection

with no action required.

  • Impact glazing is more aesthetically

appealing alternative to shutters

The use of impact resistant glazing may

Also help reduce insurance premiums.

windborne debris protection systems wind speed vs wind pressure
Windborne Debris Protection SystemsWind Speed vs. Wind Pressure
  • When choosing between a shutter system and impact resistant glazing, it is important to distinguish between wind speed and wind pressure.
  • Shutter systems can handle gusts and debris, however they cannot protect a building from wind pressure.
  • Wind pressure easily works it’s way around a shutter system to the glass surface. Impact glazing is the only solution that resists wind

pressure.

impact resistant glazing systems introduction
Impact Resistant Glazing SystemsIntroduction
  • Impact resistant glazing is created by

bonding or laminating several lites of

glass together with PVB, urethane or

resin innerlayer.

  • Insulated impact glazing has also been

developed to provide improved thermal

efficiencies.

  • When designing with impact resistant

glazing, it is important to consider the

configuration of the product in terms of

the existing or future debris field.

Tempered, Heat

Strengthened, or Annealed

Typical glass thickness:

1/8” to ¼”

PVB Thickness .090”

impact resistant glazing systems characteristics
Impact Resistant Glazing SystemsCharacteristics
  • Impact resistant glazing products consist of

multiple lites of glass that are bonded or

laminated together by a 0.06” to 0.10” innerlayer.

  • This innerlayer typically consists of PVB or in

some instances, urethane or resin.

  • The number of lites and the thickness of each

lite and the innerlayer can be varied in order to

achieve the required performance characteristics.

impact resistant glazing systems design flexibility
Impact Resistant Glazing SystemsDesign Flexibility
  • Impact glazing is typically available in

a variety of sizes and configurations,

including casement, fixed, sliding and

double and single hung windows.

  • Impact resistant glazing can also be

manufactured using tinted glass in a

variety of colors as required.

  • Reflective and low-emissivity (Low-E)

coatings can also be applied to the

glass surface in order to provide solar

and thermal control.

impact resistant glazing systems advantages of laminated glass
Impact Resistant Glazing SystemsAdvantages of Laminated Glass

In addition to impact resistance, laminated glass also provides several other

Advantages:

  • Increased Safety and Security: Laminated glass can be used as safety glazing

and offers increased resistance to forced entry. Depending on its thickness,

laminated glass can also be used to provide bullet and blast resistance.

  • Reduced Sound Transmission: Laminated glass reduces the amount of sound

that is transmitted by the glass surface. This results in higher Sound Transmission Class (STC) ratings and a quieter, more comfortable interior environment.

  • Increased Energy Efficiency: Laminated glass filters out more than 99% of the sun’s harmful ultraviolet rays. This helps reduce fading of interior materials and improves

energy efficiency.

impact resistant glazing systems insulated impact glazing
Impact Resistant Glazing SystemsInsulated Impact Glazing
  • Impact resistant glazing was originally developed

for the warmer coastal climate of Florida, there were

no requirements for thermal values.

  • As impact requirements changed up along the coast,

insulated impact glazing has become a necessity.

  • Insulated impact glazing is similar to standard impact

glazing in terms of aesthetics. The difference is the air

space between the lites of glazing.

impact resistant glazing systems insulated impact glazing cont d
Impact Resistant Glazing SystemsInsulated Impact Glazing Cont’d…..
  • Insulated impact glazing offers impact resistance, UV protection and sound attenuation similar to that of

standard impact glazing.

  • Insulated impact glazing offers superior thermal performance and significantly lower U-values.
  • The addition of a low-emissivity coating to the second glass surface can dramatically reduce solar heat gain and increase light transmittance.
impact resistant glazing systems design considerations
Impact Resistant Glazing SystemsDesign Considerations
  • In many cases, it is also important to consider the debris field that might be generated from future surrounding developments.
  • A new structure built next to an existing structure could significantly alter the potential debris field.
  • In this case, small or large missile impact glass should be considered where a potential elevated debris field exists or is expected to exist in the future.
impact resistant glazing systems design considerations cont d
Impact Resistant Glazing SystemsDesign Considerations Cont’d…….
  • Another design consideration for impact glazing is how to configure the tested products in order to accommodate larger openings.
  • In this case, tested products can be installed side by side, separated by mullions, to create bays of

windows.

  • From an engineer’s perspective, one large opening has been divided into a series of smaller openings

that meet the necessary requirements.

impact resistant glazing systems aama certification
Impact Resistant Glazing SystemsAAMA Certification
  • When specifying impact resistant

glazing systems, it is important to

look for a manufacturer who is

a member of AAMA.

  • AAMA memberships helps to ensure

quality performance and consistency

in manufacturing.

  • American Architectural Manufacturers

Association (AAMA) www.aamanet.org