NCHRP 10-80 New Specifications for Structural Supports for...
Transcript of NCHRP 10-80 New Specifications for Structural Supports for...
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.