Page 109 - Bridge and Highway Structure Rehabilitation and Repair

84 SECTION 1 ADMINISTRATIVE ISSUES

Pre-collapse deficiencies can include incorrect assumptions, data errors, incorrect analysis,

noncompliance with code guidelines, incorrect connection details, and mistakes in drawings.
Other frequent principal causes are design, detailing, and use of substandard materials.
2. Long-term fatigue and fracture (see Section 3.7, Fatigue Failures and Suggested Preventive
Actions): Failures can be due to fatigue of steel or concrete girders from repeated reversal of
stress. Brittle fracture results in the unplanned loss of service, very costly repairs, concern
regarding the future safety of the structure, and potential loss of life.

3. Failures during construction (see Section 3.8, Construction Deficiency and Suggested Preven-
tive Actions): Include constructability issues such as construction inspection, construction
supervision, quality control, use of substandard materials, and deficient design of temporary

works. Heavy construction loads and construction defects such as poor workmanship, sub-

standard materials, inadequate concrete curing, imperfections in steel, lack of fit, and lack
of quality control are other possible causes.
4. Accidental impact from ships and vessels (see Section 3.9, Vessel Collision or Floating Ice
and Suggested Preventive Actions).
5. Accidental impact from trains and defects in geometry such as vertical under clearance (see
Section 3.10, Train Accidents Causing Bridge Damage and Preventive Action).
6. Accidental impact from vehicles (see Section 3.11, Vehicle Impact and Preventive Action).
7. Failures due to blast loads (see Section 3.12, Blast Load and Preventive Action).

8. Failures due to fire damage (see Section 3.13, Fire Damage to Superstructures and Preventive
Action): Fire may result from accidental spraying of gasoline, any stored material under the
bridge catching fire, overturned vehicles, lightning, or vandalism.

9. Failures due to earthquakes (see Section 3.14, Substructure Damage Due to Earthquake and
Preventive Actions): Includes failure due to earthquake from limited bearing seat width or
plastic hinge formation.
10. Failures due to heavy winds, tornados, and hurricanes (see Section 3.15, Wind and Hurricane
Engineering).
11. Failures due to lack of inspection (see Section 3.16, Lack of Maintenance and Neglect).
Lack of maintenance or inspection leads to:
• Malfunction of bearings
• Corrosion of steel: Lack of painting. Failures due to corrosion of steel girders caused by
evaporation and condensation of river water.
12. Failures due to unforeseen events in spite of maintenance (see Section 3.17, Unforeseen
Causes Leading to Failures).
• Ice damage of piers and failure of timber fenders (unexpected loads and load combina-
tions: Force majeure
• Poor deck drainage: Negligence
• Soil settlement: Force majeure
• Freezing of bridge surface: Negligence
• Failure due to gussets or connections: Design defi ciency.
13. Failure due to experimentation: Some failures may occur due to experimentation with new
types of materials or new systems such as undefined and unpredictable material properties in

cast in place or precast construction. Although this approach may be unavoidable in certain
disciplines such as space exploration, caution is necessary.
Any one of the above factors may contribute to bridge failure or may trigger a collapse, but
failures actually occur due to a combination of loads, of which the principal or additional cause
can be one of those listed above.

Although load combinations have been defined by AASHTO LRFD Bridge Design Speci-

fications, they do not include some of those listed above.