Hurricane Wind and Wind Driven Rain Effects on Soffit Systems...• A wind‐driven rain sensor was deployed in Baytown, TX (NW of Houston) during Hurricane Ike • Front right quadrant

Hurricane Wind and Wind‐Driven Rain Effects on Soffit SystemsRain Effects on Soffit Systems

Forrest Masters PhD University of FloridaForrest Masters, PhD, University of Florida

Greg Kopp, PhD, University of Western Ontario

Jorel Vaccaro Grad Research Asst University of FloridaJorel Vaccaro, Grad. Research Asst., University of Florida

PurposePurpose

• Investigate two performance issuesest gate t o pe o a ce ssues– Structural resistance (prevent blow‐in or loss of soffit)– Water penetration resistance of venting

• Seeking to determine– Ultimate pressure capacities that can be related back

f d dto a terrain‐specific wind speed– Evaluate the installation details and choice of fastenersfasteners

• First priority is to investigate structural performance. WDR to follow..p

AgendaAgenda

• Wind Loads on SoffitWind Loads on Soffit

• Experimental Configuration

i i l i di f h b• Initial Findings from the Laboratory

• Specimen Matrix

• Structural Load Test Protocol

• Update on WDR Test Protocol DevelopmentUpdate on WDR Test Protocol Development

• Lab Tour

WIND LOADS ON SOFFITSPost‐storm damage assessments and wind tunnel studies

WIND LOADS ON SOFFITS

Occurrences of FailureOccurrences of Failure

Why?Why?

• Intense small‐scale and short‐lived pressureIntense, small scale and short lived pressure loads act on the soffit– Positive pressure when air travels up the wall– Positive pressure when air travels up the wall

– Negative pressure in regions of flow separation

T• Two causes– Flow distortion caused by the structure

– Turbulence caused by the upwind terrain

Typical Configuration of 2‐story, 4:12 Gable Roof House Model in Wind Tunnel

Pressure Taps th H

207

BACK

on the House Model

183

3.2mm Diameter

SIDESIDEROOF Case 1 Case 2

29 30 30 30 37156

31 31

Wind Directions

25 24 49 25

0 degrees

41

1.6mm Diameter

FRONT

15 96

Net Pressure Coefficients on the SoffitsNet Pressure Coefficients on the Soffits

CASE 1: Worst case for positive pressure occurs when the wind is traveling perpendicular to the

CASE 2: Worst case for negative pressure occurs when the wind is traveling parallel to the ridgeline g p p

ridgeline g p g

207

BACKPressure Taps

th Hon the House Model

183

3.2mm Diameter

SIDESIDEROOF

29 30 30 30 37156

31 31

Wind Directions

25 24 49 25

0 degrees

41

1.6mm Diameter

FRONT

15 96

Peak Pressure… Next SlideCase 1: + Pressure

5 Minute Time Series of Net P C ffi i S ffiPressure Coefficients on Soffits

Case 1: + Pressure

5 Seconds of Time Series around Peak Positive Pressure Coefficient

Converting C to Peak PressuresConverting Cp to Peak Pressures

• Pressure Coefficient = (p – pref) / ½airV2

• Wind engineers set V = mean velocity at roof height• Peak pressure = terrain dependent velocity pressure

multiplied by Cp valuemultiplied by Cp value• Consider the Saffir Simpson Hurricane Scale

SSHSWind Velocity Pressure

SSHSCategory 10 m, 60 s

Marine7 m, 1800 s

Exp. C7 m, 1800 s

Exp. C

1 75 53 7

2 96 68 12

3 111 79 16X ~0.70 0.00256V2 X Cp

4 131 93 22

5 155 110 31

SSHS Category 1SSHS Category 1

Case 1: Positive Pressure








Case 1: Positive Pressure70 psfincreasein 1 sec

Pressure Taps th H

207

BACK

on the House Model

183

3.2mm Diameter

SIDESIDEROOF

29 30 30 30 37156

31 31

Wind Directions

25 24 49 25

0 degrees

41

1.6mm Diameter

FRONT

15 96

C&C Zone 5


Case 2: Negative PressureCase 2: Negative Pressure








70 psfdecreasein 1 sec


207

BACK

183

3.2mm Diameter

SIDESIDEROOF

29 30 30 30 37156

31 31

Wind Directions

25 24 49 25

0 degrees

41

1.6mm Diameter

FRONT

15 96

SummarySummary

• Wind tunnel data shows us that the worst case pressures occur at the– Middle of the building if the wind is travelling perpendicular to the ridgeline (+ pressure case)perpendicular to the ridgeline (+ pressure case)

– Windward sidewall if the wind is travelling parallel to the ridgeline (– pressure case)

h l d h dd l k• The load change suddenly; peaks occur < 1 sec• Loss of soffit results in major susceptibility to wind‐driven rain intrusion in hurricaneswind‐driven rain intrusion in hurricanes

• How do recreate these phenomenon in the laboratory?y

EXPERIMENTAL CONFIGURATIONPressure Loading Actuators and Hurricane Simulator

EXPERIMENTAL CONFIGURATION

Experimental DesignExperimental Design

• Since the last meeting, UF and UWO haveSince the last meeting, UF and UWO have been developing the experimental method for final implementation

• University of Florida– (Supercharged) Pressure Loading Actuator( p g ) g– Hurricane Simulator– [Future] Blower System

• University of Western Ontario– 8 Pressure Loading Actuatorsg

Pressure Loading ActuatorPressure Loading Actuator

• Developed for UWO’s Three Little Pigs Project

• Replicates time varying wind‐induced pressures on the surfaces of buildings

• Pressure loads are within 5% of the target values so that overall structural loads can be accurately simulated and repeated

• Can apply the basis wind pressure time histories used by ASCE 7

Pressure Loading ActuatorPressure Loading Actuator

• Leakage through ea age t ougopenings in soffit and channels proved to be b lsubstantial

• Current configurations– UWO is using 8 units in parallel

– UF “supercharged” theUF supercharged the system with a 25 hp Spencer blower

UWO: 8 PLAs in ParallelUWO: 8 PLAs in ParallelThe soffit rig has 5 portshas 5 ports, and 3 ports connect to 2 PLAs for a total of 8 PLAs .

New Airbox DesignNew Airbox Design

UF Portable Hurricane SimulatorUF Portable Hurricane Simulator

• 2800 hp provided by four mid‐1980s twin‐turbo Dietroit Diesel motors

• Fluid power drives the vaneaxialFluid power drives the vaneaxialfans

• Aerodynamic Objectives35+ psf stagnation press re– 35+ psf stagnation pressure

– 10 ft X 9.5 ft cross‐section– 8 ‐ 44 in/hr wetting while maintaining

drop size distributiondrop size distribution

• Meets FDOT dimensions for transport

Structural Loading of SoffitsStructural Loading of Soffits

• Two resistances being investigatedTwo resistances being investigated– Structural (PLA)

Water penetration (Hurricane Simulator)– Water penetration (Hurricane Simulator)

• Both systems were employed to develop some f th i iti l fi di t d t b tof the initial findings presented next, but

ultimately it is expected that that a PLA‐style t ill b d t l d th ffitsystem will be used to load the soffits

Structural Loading of SoffitsStructural Loading of Soffits

• Developing the loads on vented soffit will notDeveloping the loads on vented soffit will not be possible with one PLA

• Currently considering solutions• Currently considering solutions– Reduce the porosity of the soffit and adjust results to full venting laterto full venting later

– “Supercharge” the PLA with a larger blower

C l th l bl t l t– Couple the larger blower to a new valve system• Easiest to transfer technology to test labs and R&D divisionsdivisions

60 hp12000 cfm at 20 in H2012000 cfm at 20 in H20128 db

INITIAL FINDINGS FROM THE LABINITIAL FINDINGS FROM THE LAB

Initial FindingsInitial Findings

1 Positive pressure on the wall correlates well1. Positive pressure on the wall correlates well with the soffit pressure

2 Flow rate through soffit is significant2. Flow rate through soffit is significant

3. Failure modes appear to be linked to sudden l di d/ f i ffloading and/or fatigue effects

Soffit vs. Wall Pressure

25

30

20

e (psf)

15

it Pressur

Tap 1

Tap 2

5

10

Soff Tap 3

Tap 4

0

0 5 10 15 20 25 300 5 10 15 20 25 30

Wall Pressure (psf)

Flow Rate through Soffit vs. Static Pressure Acting on Soffit

600

700

400

500

(cfm

/ ft2

)

300

400

ow R

ate

(

100

200Fl

00 5 10 15 20 25 30 35 40 45

Static Pressure (psf)(p )Vinyl Perforated (NFA = 6.4 sq. in / sq. ft) Vinyl Lanced (NFA = X sq. in / sq. ft) Discontinuous Vent Spaced at 4 ft

Observed Failures?Observed Failures?

• Plastic deformation (beginning of a hinge)Plastic deformation (beginning of a hinge) observed to occur midspan in the soffit panels

• Not observed in the field (that we know of)Not observed in the field (that we know of)• Undeformed soffit panels usually found on the ground post‐eventground post event

• Early indicator that the supports (channels) may be the weak point, which suggests thatmay be the weak point, which suggests that the test protocol should evaluate effects of fastener schedules and cyclic loading

Air

UWO b d f il @UWO observed failure @+40 psf and 580 cfm / sq. ft40 psf and 580 cfm / sq. ft

during the static pressure test

SPECIMENMATRIXSPECIMEN MATRIX

Specimen Matrix (Not Reduced)Specimen Matrix (Not Reduced)

Finished Wall

StuccoVinylSiding

BrickVeneer

FCBWoodLap

CMU Structural Wood Panel

VinylPerforated 1 8, 93, 104 15 ‐ 23

Soffit

VinylSolid 2 11 16 ‐ 24

Aluminum Perforated 3 ‐ 17 ‐ 25

3/8" OSB Disc. Vents 4 12 18 ‐ 26

7/16" OSB Disc. Vents 51 131 191 ‐ 271

S

3/8" Plywood Disc. Vents 6 14 20 ‐ 28

FCBDisc. Vents ‐ ‐ ‐ 21 ‐

Cont Vents ‐ ‐ ‐ 22 ‐

Wire Lath & Stucco Cont. Vents 72 ‐ ‐ ‐ ‐

1 7/16” OSB only to be tested if 3/8” OSB performs below design level2 Specimen 7 is attached through stucco3 Specimen 9 to be tested with AccuVent System4 Specimen 10 to be tested with Cor‐A‐Vent SystemSpecimen 10 to be tested with Cor‐A‐Vent System

Note: various discontinuous vent system to be tested in conjunction with Vent Covers (TBD)

Variations in MatrixVariations in Matrix

• Vinyl Soffit: Double 5” and Triple 4”y p• Aluminum Soffit: 6” wide, 12” wide double 6, 12” wide triple 4, and 16” wide quad 4

• Fastening schedule– Staples vs. NailsMi ¾” b d t i t f i f i f i l– Min ¾” embedment into framing or furring for vinyl

• Truss / Rafter Configuration• Channels attached before/after stucco application• Channels attached before/after stucco application• Hybrid systems• Use of vent coversUse of vent covers

STRUCTURAL LOAD TEST PROTOCOLSTRUCTURAL LOAD TEST PROTOCOL

Development of Test ProtocolDevelopment of Test Protocol

• Use wind tunnel dataUse wind tunnel data– Random load, where random = time varying signal with a particular statistical and spectral content

– Simplification using a sine sweep (better for replication in testing laboratories)

• Apply suction loads only• Definition of “failure”

– Deflection requirement?– Blow‐in or sucked out?

Random Load fromWind TunnelRandom Load from Wind Tunnel

Simplified Load fromWind TunnelSimplified Load from Wind Tunnel

0f = 0.15 Hz

0f = 0.25 Hz

0f = 0.35 Hz

0 5 10

-0.5

0 5 10

-0.5

0 5 10

-0.5

f = 0.45 Hz f = 0.55 Hz f = 0.65 Hz

0 5 10

-0.5

0f 0.45 Hz

0 5 10

-0.5

0f 0.55 Hz

0 5 10

-0.5

0f 0.65 Hz

0 5 10 0 5 10 0 5 10

-0.5

0f = 0.75 Hz

Cp

-0.5

0f = 0.85 Hz

-0.5

0f = 0.95 Hz

0 5 10Time (s)

0 5 10 0 5 10

UPDATE ONWDR TEST PROTOCOLUPDATE ON WDR TEST PROTOCOL

Wind‐Driven Rain ResistanceWind Driven Rain Resistance

• A wind‐driven rain sensor was deployed inA wind driven rain sensor was deployed in Baytown, TX (NW of Houston) during Hurricane IkeHurricane Ike

• Front right quadrant of the eye passed over the instrumentthe instrument

Deployed in 2008… Sponsored by

MOUNTED ON EXISTING UF HURRICANE RESEARCH INSTRUMENTED TOWERS

p y p y

WINDDRIVEN

RAIN

RAINDROPSIZE

DISTRIBUTION

RAINFALL INTENSITY

Wind‐Driven Rain ResistanceWind Driven Rain Resistance

• A wind‐driven rain sensor was deployed inA wind driven rain sensor was deployed in Baytown, TX (NW of Houston) during Hurricane Ike

• Front right quadrant of the eye passed over the instrument

• Currently analyzing the data to characterize the droplet spectra and rainfall intensity

• Will specify rain emitters (spray nozzles) based on the observed droplet size

LAB TOURLAB TOUR

Gainesville AirportNorth

POWELL LAB2160 NE Waldo Rd.

Gainesville, FL 32609

UNIVERSITY OF FLORIDAEASTSIDECAMPUS

Documents

Hurricane Wind and Wind Driven Rain Effects on Soffit Systems...• A wind‐driven rain sensor was deployed in Baytown, TX (NW of Houston) during Hurricane Ike • Front right quadrant