Page 268 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 6 APPLICATIONS OF BRIDGE DESIGN AND RATING METHODS 243

2. Sung H. Park, “Bridge Superstructure Design and Rehabilitation, Trenton, NJ - Examples
of rating and design using both WSD LFD and LRFR methods.
• LRFD design aspects for new and replacement bridges:
1. Tonias, D. and Zhao, J., Bridge Engineering - Design of composite concrete and steel
bridges using both LFD and LRFD methods.
2. Barker, R. and Puckett, J., Design of Highway Bridges - Design of single and multiple
span composite concrete; steel and wood bridges using LRFD methods.
3. FHWA, “LRFD for Highway Bridge Substructures and Earth Retaining Structures”,
Reference Manual, Publication No. FHWA-NHI-05-095.
• LFD design aspects:
1. Xanthakos, Petros P., “Theory and Design of Bridges,” John Wiley & Sons, New York,
1993.
2. PennDOT Bridge Design Training Manual, PDT- Pub. No. 302, 1994.
3. Mufti, Aftab A., Bakht, Baidar, Jaeger Leslie G., “Bridge Superstructures New Devel-
opments”, National Book Foundation, Islamabad, 1996.
4. Heins, Conrad and Lawrie, Richard, “Design of Modern Concrete Highway Bridges”,
J. Wiley and Sons, 1984.
• FHWA and NCHRP publications
• ASCE Journal of Bridge Engineering
• International conference proceedings - Bridge conferences in Pittsburgh and New York
held regularly and worldwide conferences.
• Foreign publications in English languages - Canadian codes British codes Indian Australian
and New Zealand codes.
• Short courses:
Bridge engineers are referred to specialist courses in rating or design being offered by
National Highway Institute (NHI) and some universities.
One or two day courses offered by the author on LRFD design of bridges; seismic analysis
and design; long span steel cable structures; scour analysis and design of scour counter-
measures.

6.3.8 Details of Rating Methods
The condition of a bridge is evaluated by structural assessment of its components. As de-
scribed in AASHTO Rating Manual, ratings types are:

1. Live load rating: This is used to determine the usable live load capacity by inspection and
by rating. Each component is evaluated and the lowest component rating is the most critical.
It is expressed in tons.
The load factor method used the following approach for a long time:
Rating Factor 3 (C 6 A1D) / A2 (L 4 I) AASHTO LRFR Eq. (D.6-1)
C 3 Capacity of member
D 3 Dead load effect on member
L 3 Live load effect on member
I 3 Impact factor
A1 3 Dead load factor (AASHTO LRFR D 6.5.2)
A2 3 Live load factor (AASHTO LRFR D 6.5.3)