vessel collision in the high marine environment in high seas.ppt

physics of vessels dynamics

1. BRIDGE ANALYSIS AND
DESIGN
A PRESENTATION ON
DESIGN OF PIERS
FOR
VESSEL COLLISION FORCE

2. Mississippi River Bridge

3. Sunshine Skyway Bridge, May 9, 1980
after being struck by the M/V Summit
Venture.

4. Scope of Work
THE BASIC INTENT OF THIS STUDY IS
THE DETERMINATION OF VESSEL
COLLISION FORCES ON SUB
STRUCTURE (PIERS), ITS
APPLICATION AND COMBINATION
RULES.
METHODS OF ANALYSIS AVAILABLE
BRIDGE PROTECTION IN A NAVIGABLE
WATERWAY AGAINST VESSEL
COLLISION

5. Introduction
Bridges located over the navigable
waterways could be threatened by the
accidental impact of passing ships.
The basic intent is to provide bridge
components a reasonable resistance
against ship and barge collisions

6. Introduction
All bridge components in a navigable
waterway crossing, located in design water
depths not less than 600mm, shall be
designed for vessel impact in accordance
with AASHTO specifications
The risk concept is usually applied to
determine the bridge safety. The risk could
be defined as combination of probability and
consequences of given kind of accident

7. Design criteria
Selection of design vessels
Estimates of sizes of impact loads
Rules for application of loads
Types of collision
Bow collisions
sideway collisions

8. Factors Effecting vessel
collision
SELECTION OF BRIDGE SITE
SELECTION OF BRIDGE TYPE AND
CONFIGURATION
HORIZONTAL AND VERTICAL CLEARANCE
APPROACH SPANS
WATERWAY CHARATCTERSTICS
CHANNEL LAYOUT AND GEOMETRY
WATER DEPTH AND FLUCTUATIONS
CURRENT SPEED AND DIRECTION

9. Overall risk to the Bridge(AF)
Method I (AASHTO Guide)
1.Collect vessel and waterway data
2.Select design vessel and compute
collision loads
Method II (AASHTO Guide, AASHTO LRFD)
1.Collect vessel, navigation, waterway
and bridge data
2.Perform probability based analysis and
select pier capacities

10. AASHTO Method II
AF = (N) (PA) (PG) (PC)
AF = Annual Frequency of Collapse
N = Annual Number of Vessels
PA = Probability of Vessel Aberrancy
PG = Geometric Probability
PC = Probability of Collapse
AF acceptable: < 0.0001 for Critical
Bridges
< 0.001 for Regular Bridges

11. Annual number of vessels, N
Number of vessels N, grouped by
Type
Size and shape
Loading condition
Direction of traffic
Adjusted for the water depth at each
pier

12. Probability of Vessel
Aberrancy, PA
PA = (BR) (RB) (RC) (RXC) (RD)
BR = Aberrancy base rate
RB = Correction factor for bridge location
RC = Correction factor for parallel current
RXC=Correction factor for cross-currents
RD = Correction factor for vessel density

13. Waterway
Regions for
Bridge Location
Correction factor
for bridge location,
RB

14. Geometric Probability, PG
Models the location of an aberrant
vessel relative to the channel
Quantifies the conditional probability that
a vessel will hit a pier given that it is
aberrant
Accounts for the lower likelihood of an
aberrant vessel being located further
away from the channel
Accounts for Pier Protection

15. Geometric
Probability Model
Normal Distribution
with σ = LOA
Geometric Probability
of Pier Distribution

16. Probability of Collapse, PC
Reduces AF by a factor that varies from
0 to 1
PC = 0.1+9(0.1-H/P) if 0.0<= H/P <0.1
PC = (1.0-H/P)/9 if 0.1<= H/P <1.0
PC = 0.0 if H/P >=1.0
where:
H = resistance of bridge component
P = vessel impact force

17. Ship Collision Force on
Pier, P
S
P
S
= 1.2x10
5
x V (DWT)
1/2
P
S= Equivalent static impact force (N)
DWT = Deadweight tonnage (Mg)
V= Vessel collision velocity (m/sec)

18. Ship Impact Force,
P
S
Figure Shows
Typical Ship Impact
Forces

19. Barge Collision Force on
Pier, P
B
If a
B
< 100mm
P
B
= 6.0 x 10
4
a
B
If a
B > 100mm
P
B = 6.0 x 10
6
x 1600 x a
B
Where:
P
B =Equivalent static barge impact
force. (N)
a
B
=Barge bow damage length (mm)

20. Barge Impact
Force, P
B
Figure Shows
Typical Hopper
Barge

21. Application of impact forces
Collision forces on bridge substructures
are commonly applied as follows:
100% of the design impact force in a
direction parallel to the navigation
channel (i.e., head-on)
50% of the design impact force in the
direction normal to the channel (but
not simultaneous with the head-on
force)

22. Application of impact forces
For overall stability, the design impact
force is applied as a concentrated
force at the mean high water level;
For local collision forces, the design
impact force is applied as a vertical
line load equally distributed along the
ship’s bow depth for ships.

23. Bridge protection systems
Piers exposed to vessel collision can
be protected by special structures
designed to absorb the impact loads
they are:
Fender Systems
Pile-Supported Systems
Dolphin Protection Systems
Island Protection Systems
Floating Protection Systems