Page 267 - Bridge and Highway Structure Rehabilitation and Repair

242 SECTION 2 STRENGTHENING AND REPAIR WORK

10. Railway engineer for bridges locate over railroad for span length and construction
issues
11. Vendors for availability of products in time. Examples are: Precasting; welded and
bolted connections; bearings; deck joints; water proofing post-tensioning; repair

materials and any special products etc.
12. Ensuring availability of high performance steel; high performance concrete
13. Obtaining approval from client for using a commercial software
14. Project management: Client coordination; In-house progress meetings; setting mile-
stones and submission dead lines.
6.3.5 Design Requirements

All calculations are code based. LRFD Specifications and LRFR Manual for Condition
Evaluation have provided design and rating guidelines. There are dozens of formulae in each
chapter which need to be understood.
Rehabilitating designing and constructing may cost multi-billion dollars for highway and
transit structures; the cost of NJ Turnpike widening project on which author worked recently is
alone worth 3 billion dollars while cost for Oakland Bay Bridge in San Francisco is over twice
as much.
In this book emphasis is laid down on explaining and extending AASHTO codes for design
and rating. LRFD numerical examples such as for deck slab replacement and the necessary steps
for concrete and steel bridges are given. Focus is on concepts rather than details.

The difficulties in giving too many examples are that they become specific for each revision
of AASHTO code. With changing regulations solved examples cannot be used with latest revi-
sions and it may sometimes even be misleading when using a superseded procedure.
Computer programs are also being revised and the output format also changes.
Advantage of hand calculations seems to be in preliminary sizing of members or checking
the results of a computer output.
Most highway agencies no longer request formal design calculations as part of the submis-
sion and others only require computer solutions of approved software.
Use of computer has the advantage that any errors in arithmetic or misuse of units are
avoided.

6.3.6 Rating Aspects for Existing Bridges
Rating is dependent upon:
• Magnitude of live load
• Intensity and frequency of traffi c
• Number of lanes
• Existing conditions of structure
• Bridge age
• Material properties

6.3.7 Knowledge Database for Rating and Design

Excellent LRFD solved examples are provided on various aspects in the following text books.
These numerical examples may be referred to for use in detailed rating and design calculations
as they are useful in understanding the subject fundamentals.
The following references are available on the subject of rating and design:
1. AASHTO Manual for Condition Evaluation for LRFR—Rating formula generally refer to
AASHTO LRFD Specifi cations.