Structural Analysis and Design for Signal and Lighting Systems

Florence Hutcheson Lee Sewell, PE, SE conducted an in-depth structural analysis known as SALSA to examine wire span, mast arm, and high mast structures. This comprehensive study, initiated in 2007, aimed to enhance the geotechnical evaluations of pole bases to meet current standards. Through innovative design methods and modeling, the project minimized the need for site-specific geotechnical investigations, addressing various soil types and slope conditions effectively. The use of safety factors guided the design process, ensuring structural integrity and load-bearing capacity.

• Structural Analysis
• Signal Lighting Systems
• Geotechnical Evaluations
• Safety Factors
• Innovative Design

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1. FLORENCE & HUTCHESON LEE SEWELL, PE, SE

2. SIGNAL AND LIGHTING STRUCTURAL ANAYLSIS (SALSA) ANALYZES WIRE SPAN, MAST ARM AND HIGH MAST STRUCTURES

3. STARTED IN 2007 EXPAND ON EARLIER GEOTECHNICAL EVALUATIONS DONE BY DARRIN BECKETT IN 2004. AT THE TIME, POLE BASES DIDN T HAVE DOCUMENTED DESIGN. 10FT BASE BRING THE DESIGN UP TO CURRENT CODE. AASHTO STANDARD SPECIFICATIONS FOR STRUCTURAL SUPPORTS FOR HIGHWAY SIGNS, LUMINAIRES AND TRAFFIC SIGNALS.

4. REMOVE THE NEED FOR PERFORMING SITE- SPECIFIC GEOTECHNICAL INVESTIGATIONS. CHALLENGES ENCOMPASS ALL TYPES OF SOIL THAT COULD BE ENCOUNTERED CONSERVATISM

5. MODELED FOUNDATIONS UNDER VARYING SOIL AND SLOPE CONDITIONS. COHESIVE AND COHESIONLESS SOILS AND ROCK COHESION = 1 KSF FRICTION ANGLE = 30 DEG 3:1, 2:1, 1.5:1

6. DIAMETER DRIVEN BY ANCHOR BOLT CIRCLE OF POLES 36 MAST ARM AND WIRE SPAN POLES 48 HIGH MAST EMBEDMENT (AASHTO 13.6.1) BROMS DESIGN METHOD BASED ON ULTIMATE STRENGTH DESIGN, SO SAFETY FACTORS ARE APPLIED TO SHEARS AND MOMENTS.

7. BROMS DESIGN METHOD SAFETY FACTORS (AASHTO RECOMMENDS) UNDERCAPACITY FACTOR OF SOIL: 0.7 OVERLOAD FACTOR FOR LOADINGS: 3 SAFETY FACTOR = 4.3 THE HIGH SAFETY FACTORS WERE AGREED ON BY THE GEOTECHNICAL DEPARTMENT DUE TO THE UNCERTAINTY OF THE TYPE OF SOIL.

8. DESIGN TABLE DEVELOPED

9. AASHTO SECTION 3: LOADS OUTLINES LOADING ON POLES AND ATTACHMENTS SALSA IS USED TO FIND LOADS ON POLE BASES

11. ANALYZES WIRE SPAN, MAST ARM AND HIGH MAST STRUCTURES MAST ARM AND HIGH MAST LOADS ARE FOUND BY SIMPLE STATICS SPAN WIRE ANAYLSIS DETAILED METHOD OF ANALYSIS AASHTO A8

12. MAST ARM AND HIGH MAST LOADING FOR BASE DESIGN WIRE SPAN LOADING FOR BASE DESIGN LOADING FOR POLE SELECTION FROM STORAGE YARD

13. WIRE SPAN POLE SELECTION PREVIOUS DESIGN IN-HOUSE SPREADSHEET FOR WIRE SPAN STRUCTURES NEGLECTED WIND AND ICE LOADS SALSA CALCULATES MOMENTS COMPARES THEM TO THE ALLOWABLE MOMENTS FOR POLES IN THE YARD.

14. PROBLEMS EXCEL COMPATIBLITY DELIVERY LIMITATIONS

15. MOVING TO A WEB BASED APPLICATION

16. WEB BASED ADVANTAGES GREATER ACCESS FILE SHARING UPDATES ARE SEAMLESS MORE USER FRIENDLY

17. POSSIBLE ADVANCEMENTS STATEWIDE SOIL PROFILING ADDITIONAL FEATURES POLE BASE VOLUME CALCULATOR ATTACHMENT HEIGHT PLACEMENT