Page 106 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 3 BRIDGE FAILURE STUDIES AND SAFETY ENGINEERING 81

The final result from analyzing many indicatorsleads to an understanding of the manner of
explosion and magnitude of the explosion source energy. Correlation methods used are:
1. Semi-empiricaldamage correlations to single-degree-of-freedom analysis.

2. Semi-empiricaldamage correlations to dynamic nonlinearfinite element analysis.
3. Use of multiple damage indicators to identify the manner of explosion.

3.2.6 Preparing Judicial Reports
An investigation report will clearly identify the reasons behind the failure and will cover
any administrative and technical lapses or force majeure.
Knowledge of state and federal laws addressing the rights of victims affected by the disas-
ter will be required. Training in global bridge engineering to include forensic engineering is
desirable for designers to appreciate the consequences of failures resulting from their actions
or inactions. Continuing education seminars to create interest in objective designing need to be
made mandatory.

3.3 MANY ASPECTS OF FAILURES
1. Table 3.1 lists additional causes in light of more recent events. They may be identifi ed on
the basis of old and new technology.
Additional causes of failures may be listed as:
• Joints and connection failures (I-35W bridge failure in Minnesota)
• Tornados and hurricanes (Louisiana disaster from Hurricane Katrina)
• Bomb blast and vandalism (a bridge collapse in Manchester, New Hampshire and the 1992

A406 flyover in England)
• Ice damage (author’s structural solutions as structural engineer for timber fender col-
lapse at the navigable Delaware and Raritan River bridges for the New Jersey Turnpike
Authority)
• Earthquake damage to bridges in Pakistan (author was a member of the U.S. AID Team
which compiled a reconstruction report after the 2005 earthquake)
• Scour collapse of Peckman’s River Bridge from Hurricane Floyd (the six-lane collapsed
bridge on Route 46 was replaced with an integral abutment bridge, using deep pile foun-
dations and shielded with sheet piling).
2. Failures during construction and due to earthquakes have been much higher than those shown
by the earlier studies and need to be taken seriously in designing for construction loads or
for seismic events.
3. Design and detailing errors need to be minimized with QA/QC procedures and checking.
4. In the past, less attention has been paid to extreme events and construction conditions. How-
ever, AASHTO LRFD Bridge Design Specifications have included both extreme events and

construction loads in design. Further research is needed in these relatively new disciplines.

3.4 A DIAGNOSTIC APPROACH
3.4.1 Comparative Study of Failures

The identification and diagnosis of failures is the starting point for meeting rehabilitation
objectives and drafting a comprehensive code of practice for design. The author has carried out
in-depth studies of such causes and their prevention from many independent sources. Only fi ve
major sources are listed here:
1. According to Jean Louis Briaud of Texas A&M, a great number of bridges continue to fail
due to flood, collision, and overload. Bridges with narrow waterway openings and erodible

soils are most susceptible to bridge collapse.
Other frequent principal causes are design, detailing, construction, and material defects.