Hamilton Creek Bridge Introduction

1
Hamilton Creek Bridge Introduction
This presentation will look at

• Possible causes of the deterioration.

• When the bridge will become unsafe and need
  replacing.

2006 County of Placer, California viewed 31st
August 2006 http//www.placer.ca.gov/business/film
s/locations/images/7a.html
2
Hamilton Creek BridgeBasic Bridge Information

• Built in 1940.
• Australian hardwood timber- Syncarpia Glomulifera
  (Turpentine)
• Estimated thickness for the entire bridge deck
  structure at 700mm.
• 3.8metres wide.
• 24m long.
• The main columns or piers were initially 500mm
  diameter.

MUKUND MURTY viewed 31st August
2006.http//www.bharat-rakshak.com/IAF/History/194
0s/Shitoley01.html,
3
Hamilton Creek Bridge Deterioration
The main cause of deterioration is most likely to
be weathering.
Weathering is a natural process caused through
exposure to

• sunlight
• wind
• rain
• dew
• frost and
• fumes.

Timber Research Team, Timber Building In
Australia, Weathering of Timber, viewed 13th
August 2006,lthttp//oak.arch.utas.edu.au/tbia/view
_article.asp?articleID160gt
4
Hamilton Creek Bridge Deterioration

• To help slow or stop the process of weathering
  wood can be applied with

1. Paint
2. Water repellents
3. Water-repellent preservatives or
4. Pigmented penetrating stain.
Clear coatings should be avoided as they will not
fully protect the wood.
Timber Research Team, Timber Building In
Australia, Weathering of Timber, viewed 13th
August 2006,lthttp//oak.arch.utas.edu.au/tbia/view
_article.asp?articleID160gt
5
Hamilton Creek Bridge Deterioration

• Other possible causes for the deterioration could
  be

1. Exposure to chemicals
2. Termites
3. Lyctids
4. Furniture Beetles
All these possible causes will speed up the
deterioration of the piers.
6
Hamilton Creek Bridge Deterioration
Generally weathering is an extremely slow
process, with an average erosion of only 6mm lost
per 100 years as

• Checks and cracks may develop.
• Water continues to be absorbed and desorbed by
  the surface.

Timber Research Team, Timber Building In
Australia, Weathering of Timber, viewed 13th
August 2006, lthttp//oak.arch.utas.edu.au/tbia/vie
w_article.asp?articleID160gt
7
Hamilton Creek Bridge Deterioration
3. Eventually untreated interior sections of
the timber are exposed. 4. Timber loses
strength.
8
Bridge Calculations

• Calculations and Recommendations

9
Assumptions
In order to calculate when the bridge will need
to be replaced assumptions have been made about
the vehicle load and timber piers.
10
Vehicle Assumptions

• The maximum vehicle load is 65 ton.

• The vehicle load is supported evenly over the
  bridge.

11
Timber Pier Assumptions

• The timber has been exposed to normal
  environmental conditions.

• There was no internal rotting to the piers when
  they were first installed.

• The strength of the pier timber is F11. This is
  the worst-case scenario.

12
Calculations
Calculations are based on the survey conducted by
S.S Smith.
Based on the results of S. S Smith
13
Calculations
Based on the results of S. S Smith
14
Predicted Cross Section Decay
The following graph represents the total decay of
the piers.

• The bridge has been unsafe to carry a 65 tonne
  load since 2002.

Based on the results of S. S Smith
Based on the results of S. S Smith
15
Final Results

• Based on our calculations and the assumptions
  that have been made our conclusion is that the
  bridge will
• become unsafe 62 years after construction.
  (2002)
• need to be replaced immediately
• not be able to carry a 65 tonne truck
• only be able to hold a maximum weight of 57
  tonnes.

To come to a more definitive conclusion more
specific information on the bridge and its load
will be required. The information in the report
should only be used as a guide while further
investigations into the bridge are made.