NCHRP 10-80 New Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals

AASHTO SCOBS Meeting Columbus, OH

June 2014

Jay Puckett, PE, Ph.D., BridgeTech and University of Wyoming

(project overview)

Norm McDonald, PE, Iowa DOT (agenda items)

Team

• Jay Puckett, UW and Bridgetech

• Michael Garlich & Jerome Koonce, Collins Engineers

• Michael Barker, Consultant

• Sougata Roy, Lehigh

• Robert Connor, Purdue

• Andy Nowak, U of Nebraska

• Craig Menzemer, U of Akron

• Karl Frank, Hirschfield

• Mark Jablin (BT), Anna Rokoczy (UNL)

DIVISON I: Load and Resistance Factor Design

SECTION 1: INTRODUCTION SECTION 2: GENERAL FEATURES OF DESIGN SECTION 3: LOADS SECTION 4: ANALYSIS AND DESIGN—GENERAL CONSIDERATIONS SECTION 5: STEEL DESIGN SECTION 6: ALUMINUM DESIGN SECTION 7: PRESTRESSED CONCRETE DESIGN SECTION 8: FIBER-REINFORCED COMPOSITES DESIGN SECTION 9: WOOD DESIGN SECTION 10: SERVICEABILITY REQUIREMENTS SECTION 11: FATIGUE DESIGN SECTION 12: BREAKAWAY SUPPORTS SECTION 13: FOUNDATION DESIGN

Same

organization

Calibration

SECTION 14: MATERIALS, DETAILING, AND FABRICATION

SECTION 15: CONSTRUCTION

Division II – Fabrication and Construction

Some materials

moved from LTS-6 design sections

Led by Collins Engineers

SECTION 16: INSPECTION AND REPORTING (ADVISORY)

SECTION 17: MANAGEMENT (ADVISORY)

Division III – Asset Management

New materials

Led by Collins Engineers

LRFD Format

i i n r

i

i

n

r

Q R R

load factors

Q load effects

resistance factors

R resistance

R factored resistance

SECTION 3: LOADS

Move to ASCE 7-10 from ASCE 7-05 (major change)

Gust effects: G = 1.14 as a minimum

Section 3: Loads Wind Pressure ASCE/SEI 07-10

20.00256z z d dP K K GV C2

α

2.0

zg

zK

z

Gust effects: G = 1.14 as a minimum

Cd = same except for update from 10-74

Notes:

1. Values are nominal design 3-s gust wind speeds

in m/s (mph) at 10 m (33 ft) above ground for

Exposure C category,

2. Linear interpolation between wind contours is

permitted.

3. Islands and coastal areas outside the last contour

shall use the last wind speed contour of the

coastal area.

4. Mountainous terrain, gorges, ocean

promontories, and special wind regions shall be

examined for unusual wind conditions.

5. Wind speeds correspond to approximately a 7%

probability of exceedance in 50 years (Annual

Exceedance Probability = 0.00143, MRI = 700

Years)

Category II

Category II: 7% probability of

exceedance in 50 years (Annual

Exceedance Probability = 0.00143,

MRI = 700 Years)

90 mph (’05)

2115

1.28 1.6390

2.3.2 Basic Combinations ASCE 7-2010

Structures, components, and foundations shall be designed so that their design strength equals or exceeds the effects of the factored loads in the following combinations:

1. 1.4D

2. 1.2D + 1.6L + 0.5(Lr or S or R)

3. 1.2D + 1.6(Lr or S or R) + (L or 0.5W)

4. 1.2D + 1.0W + L + 0.5(Lr or S or R)

5. 1.2D + 1.0E + L + 0.2S

6. 0.9D + 1.0W

7. 0.9D + 1.0E 2

1151.28 1.63

90

ASCE/SEI 07-10 Risk Categories

Risk Category

Short Description

I Low risk to human life

II Typical structures

III Substantial economic Impact

IV Essential facilities or hazardous

Consequences of Failure Risk Category (MRI)

Traffic Volume

Typical High Low

ADT<100 300 1700 300

100<ADT≤1000 700 1700 300

1000<ADT≤10000 700 1700 300

ADT>10000 1700 1700 300

Typical: Failure could cross travelway

High: Support failure could stop a life-line travelway

Low: Support failure could not cross travelway

Roadside sign supports: Use 10 years

Wind-on-Ice Analysis

(a)

(b) (c)

Assumptions

Example 1

Design Wind Load 110 mph

CD 0.55

Max Ice Load on ASCE Map

1.5 in

Coincident Wind for equal load effect

95 to 97.5 < 110 mph

Common Data

Diameter, in 12 to 16

Thickness, in 0.25 to 0.5

Steel density, pcf 490

Ice density, pcf 58

Example 2

Design Wind Load 110

CD 0.55

Max Coincident Wind Load on ASCE Map

60

Ice thickness 3.18 to 3.37 > reasonable

LRFD Load Combinations

LRFD Load Combinations

LRFD Load Combinations

LRFD Load Combinations

Wind Load Direction Combinations

W

W 0.75 W

0.75 W

1.32 x single

1

2.5

~ 75 80 .

u u

r r

arm centroid pole

M T

M T

L x L

to ft arm

Load Case 1 Load Case 3 Load Case 3

SECTION 5: STEEL DESIGN

• Use full Mp where compact (Z/S = ~1.33)

• Interaction for axial, torsion, flexure, and shear

• Moved fabrication, detailing, and construction articles to Division II

2

1.0u u u u

r r r r

P BM V T

P M V T

SECTION 6: ALUMINUM DESIGN

• Follows Aluminum Design Specification 2010

• Moved fabrication, detailing, and construction articles to Division II

• Agenda item includes new Section 13 and 14 (85% rule)

Section 11: Fatigue

• NCHRP 10-70(Fatigue Resistance) [Roy et al]

• University of Texas Pooled Fund Study (Resistance) [Frank et al]

• NCHRP 10-74 (High-level Pole Fatigue Loads) [Connor et al]

Follows AASHTO LTS-6 with reorganization

and minor editorials, etc..

Reliability Index

Dead-to-Wind Load Ratio

Significant dead load effect

Wind load higher

Calibration

• Coastal regions

• Central US and Western US

• Southern Alaska

• West Coast

20.00256z z d dP K K GV C

COV & Bias for each area

10 sec

Calibration

1. Set trial load and resistance factors (D, W, f)

2. Optimal Design for LRFD and ASD (Performance Ratio = 1.0)

3. Determine b

4. Change W/(W+D)

5. Repeat Example computations

700-Year MRI

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

00.20.40.60.811.2

Be

ta

M Wind/M Total

Average Beta - 700 Year

LRFD

ASD

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

00.20.40.60.811.2

Bet

a

M Wind/M Total

Minimum Beta - 700 Year

LRFD

ASD

f 0.90

D 1.10 1.25

W 1.00 0.00

1700-Year MRI

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

00.20.40.60.811.2

Be

ta

M Wind/M Total

Average Beta - 1700 Year

LRFD

ASD

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

00.20.40.60.811.2

Bet

a

M Wind/M Total

Minimum Beta - 1700 Year

LRFD

ASD

f 0.90

D 1.10 1.25

W 1.00 0.00

300-Year MRI

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

00.20.40.60.811.2

Bet

a

M Wind/M Total

Minimum Beta - 300 Year

LRFD

ASD

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

00.20.40.60.811.2

Be

ta

M Wind/M Total

Average Beta - 300 Year

LRFD

ASD

f 0.90

D 1.10 1.25

W 1.00 0.00

Reliability Index with MRI

Midwest & West Reliability Index

(Midwest and West)Load Ratio [WL/(DL+WL) = 0.5]

Risk Category

Traffic Volume Typical High Low

ADT<100 3.03 3.89 3.03 100<ADT<=1000 3.60 3.89 3.03 1000<ADT<= 10000 3.60 3.89 3.03 ADT>10000 3.89 3.89 3.03 Typical: Failure could cross travelway

High: Support failure could stop a life-line travelway Low: Support failure could not cross travelway

Roadway sign supports: use 10 years (Low) (Midwest and West)Load Ratio [WL/(DL+WL) = 1.0]

Importance

Traffic Volume Typical High Low

ADT<100 2.77 3.62 2.77

100<ADT<=1000 3.35 3.62 2.77

1000<ADT<= 10000 3.35 3.62 2.77

ADT>10000 3.62 3.62 2.77

Typical: Failure could cross travelway

High: Support failure could stop a life-line travelway

Low: Support failure could not cross travelway

Roadway sign supports: use 10 years (Low)

Risk Category

Traffic Volume Typical High Low

ADT<100 300 1700 300

100<ADT≤1000 700 1700 300

1000<ADT≤10000 700 1700 300

ADT>10000 1700 1700 300

Typical: Failure could cross travelway High: Support failure could stop a life-line travelway

Low: Support failure could not cross travelway

Roadside sign supports: Use 300 years

Flexural Effects

0.60

0.70

0.80

0.90

1.00

1.10

1.20

00.20.40.60.811.2

Rat

io

M Wind/M Total

LRFD Required Resistance Ratios (RnT/Rn700)

Rn300/Rn700

Rn1700/Rn700

Flexural Effects

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

00.20.40.60.811.2

Rat

io

M Wind/M Total

Required Resistance Ratios (LRFD/ASD)

LRFD/ASD

WIND has

HIGHER

Variability

Makes

Sense

Examples

MathCAD and PDF

DIVISION II & III - OUTLINE

• DIVISION II – FABRICATION & CONSTRUCTION

– Section 14 Materials, Detailing, and Fabrication

– Section 15 Construction

• DIVISION III – ASSET MANAGEMENT

– Section 16 Inspection and Reporting (advisory)

– Section 17 Management (advisory)

Led by Collins Engineers

SECTION 14 - FABRICATION

• Reference AASHTO Bridge Construction Specifications and AWS for steel and aluminum

• Limited information currently available (for steel and aluminum) regarding fabrication will be relocated

SECTION 14 - FABRICATION

14.1 – Scope

14.2 – Working Drawings

14.3 – Steel Structures

14.4 – Aluminum Structures

14.5 – Prestressed Concrete Structures

14.6 – Composite (Fiber Reinforced Polymer) Structures

14.7 – Wood Structures

14.8 – References

SECTION 15 - CONSTRUCTION

• Primarily reference applicable portions of the AASHTO LRFD Bridge Construction Specifications

• Current state practice and provisions

• Proper fastener tightening and connection fit-up of end plates

• Information to achieve a structural grout pad if desired

SECTION 15 - CONSTRUCTION 15.1 – General

15.2 – Erection

15.3 – Anchor Bolts

15.4 – Bolted Connections

15.5 – Steel Structures

15.6 – Aluminum Structures

15.7 – Prestressed Concrete Structures

15.8 – Composite (Fiber Reinforced Polymer) Structures

15.9 – Wood Structures

15.10 – Foundations

15.11 – References

SECTION 16 – INSPECTION & REPORTING (advisory)

• Written more toward advisory since current regulation does not mandate inspections of ancillary structures

• Currently FHWA has a document on the inspection of ancillary structures

• More general treatment to assure that a consistent and proper inspection is performed

Thank You!

Disclaimer

This investigation was sponsored by TRB under the NCHRP Program. Data reported are work in progress. The contents of this article (presentation) have not been reviewed by the project panel or NCHRP, nor do they constitute a standard, specification, or regulation.

Our team is responding to Panel comments – many are included in

the draft LRFD-LTS to be discussed.