OVERVIEW

CSA DESIGN SPECIFICATIONS

FOR HML

Jay PuckettRebecca Johnson

Emily Ahearn

Civil and Architectural EngineeringUniversity of Wyoming

AASHTO T-12Sacramento, CA

2010

AASHTO 11.7.2

Band-Limited Flow(disorganized)

Sinusoidal(Organized)

CSA Implementation

Frequency Deflection

Acceleration Mass

BB A C KG R O U N DA C KG R O U N D

MOUNTAIN PLAINS CONSORTIUM RESEARCH:

Use of Wind Power Maps to Establish Fatigue Design Criteria for

Traffic Signal and High-Mast Structures

Traffic Signal Arm

High-Mast Pole

BB A C KG R O U N DA C KG R O U N D

CONCLUSIONS:

TRAFFIC SIGNAL ARMS

HIGH WIND

XHIGH-MAST POLES

PURPOSE:

BB A C KG R O U N DA C KG R O U N D

VORTEX SHEDDING

• Occurs when fluid passed over a bluffed object

• Alternating pressure zones with frequency,

• Across-wind movement

Vortex Overview

Regimes of fluid flow across smooth circular cylinders (Lienhard, 1966)

CSA 2006

Mode 1 Mode 2 Mode 3 Mode 4

Section

BSection

C

Join

t1

Join

t2

Accelerometer

Accelerometer

56 ft

41 ft

33 ftAnemometer

4x StrainGauges

V-Link

5 ft

Section

A

Mode 1 2 3 4

SAP Natural Freq (Hz) 0.385 1.64 4.22 8.27

Actual Natural Freq (Hz) 0.35 1.5 3.8 7.5

% Difference 9.0% 8.6% 9.9% 9.3%

Damping Ratios (%) 0.5 0.3 0.1 --

HML -- 120 ft.

CSA requires modal analysis

LaramiePole

Wind Characteristics

Original Imagecourtesy ofSymscape'http://www.symscape.com/

CSA 2006

Wind StochasticsF

requency

(%)

Wind Speed, mphMean = 13.7 mph

LaramiePole

Overview

Mode 1 Mode 2 Mode 3 Mode 4

Secti

on

BS

ecti

on

C

Join

t1

Join

t2

Accelerometer

Accelerometer

56 ft

41 ft

33 ftAnemometer

4x StrainGauges

V-Link

5 ft

Secti

on

A

MathematicalModel =

Load Effect

Fatigue Prediction Model

• Design• Inspection Support• Management Support

Today’s Focus -- CSA

0

0.05

0.1

0.15

0.2

0.25

0.3

0 5 10 15 20 25 30

Acc

ele

rati

on

(g)

Wind Speed (mph)

Crosswind

ExperimentalResults

Height Dcrit

ft in Mode 1 Mode 2 Mode 3 Mode 4

Mode 4 - Antinode 1 32 18.8 53.5

Mode 3 - Antinode 1 46 16.9 22.9

Mode 4 - Antinode 2 72 13.5 32.4

Mode 2 - Antinode 1 75 13.1 6.2

Mode 3 - Antinode 2 97 10.2 11.8

Mode 4 - Antinode 3 104 9.3 20.6

Mode 1 - Antinode 1 120 7.18 0.72

Critical Velocity at 33 ft (mph)Location

Predicted CriticalVelocity

60 sec average

LaramiePole

Mechanics Overview

Uniform FlowRigid CylinderAerodynamic (no fluid-structure interaction)

Mechanics Overview

Uniform FlowFlexible Cylinder SupportAeroelastic (fluid-structure interaction)

LaramiePole

Mechanics OverviewUniform FlowRigid Prismatic CantileverAerodynamic (no fluid-structure interaction)

Mechanics OverviewUniform FlowFlexible Prismatic CantileverAeroelastic (fluid-structure interaction)

Mechanics OverviewNon uniform FlowFlexible Prismatic CantileverAerodynamic (no fluid-structure interaction)

x

Mechanics OverviewNon uniform FlowFlexible Prismatic CantileverAeroelastic (fluid-structure interaction)

Mechanics OverviewNon uniform FlowFlexible Tapered CantileverAeroelastic (fluid-structure interaction)

wi, miV(x), m, r

Vref

D(x)

CSA OverviewNon uniform FlowFlexible Prismatic CantileverAeroelastic (fluid-structure interaction)

CSA OverviewNon uniform FlowFlexible Tapered CantileverAeroelastic (fluid-structure interaction)

Generalized Coordinates

1. Assume a shape function

U=1

x

m(x)

2. Determine equivalent SDOF

f(x,t)

3. Solve however you wish (linear)CSA Overview

fs(x,t)

CSA Overview

Band-Limited Flow(disorganized)

Sinusoidal(Organized)

Likely we are onlyin larger values

CSA Implementation

Frequency Deflection

Acceleration Mass

• Strouhal Number

• Natural Frequency

• Wind Speed Fit

Vortex SheddingExcitation

• Equation Estimation

• Found from SAPModel by Emily

Modal Shapes• Band-limiting

random process forsmall disp.

• Harmonic Lock-in iflarge

Modal Coefficientof Magnitude

• Velocity “bin size”chosen

• Macros written toloop from low tohigh velocities

Velocity Looping

EXCEL PROGRAMMING

DISPLACEMENTS: A3.2.4.3.1

Luminaire Mass mlum 272.1554 kg 600 lb

Strouhal number S 0.18

RMS Lift Coeff. CL 0.5 bin size lower upper

Band Width B 0.25 1 11 12 mph

Correlation Length L 2.5 4.917 5.364 mps

Air Density ρ 0.929071 kg/m3

0.058 lb/ft3

Structural damping ε 0.005 0.003 0.001 max velocity 50

Natural Frequency ni 0.34 1.5 3.9 (mph)

wind velocity profile α 0.143

Base Diameter Do 24.25 in

tapering angle θ 0.005833 radians

0.3342 degrees

Control Velocity at 10m

velocity ranges (mps)

Set Current to Max

SPREAD SHEET OUTPUT

LaramiePole

COMPARISON OF OUTPUT TO FIELD DATA

Dsmax ~1.8 ksiDmax ~0.9 in

Perforated ShroudPerforated Shroud HDPE net, 45% open area

16 ft long

Covers pole from 89 to 105 ft

Dshroud = 1.25Dpole

Height (ft) Cpole (in) Cshroud (in)

91 33.8 42

95 32.0 40

99 30.3 38

103 28.5 36

0

0.05

0.1

0.15

0.2

0.25

0.3

0 5 10 15 20 25 30

Acc

ele

rati

on

(g)

Wind Speed (mph)

Unretrofitted

Perforated Shroud

Perforated ShroudPerforated ShroudMaximum Acceleration vs. 30s Mean Wind

Speed

END OF TALK

Appendix – not presented

Extra – project description

Analysis ModelCSA, ISU, other

Fat

igu

e-li

feP

red

icti

on

Readily Available Wind DataDesignInspectionModels