hampden bridge for structures

7/30/2019 hampden bridge for structures

1/12

PROJECT : Hampden Bridge

Engineer :Percy Allan

Owner : City of Wagga Wagga

Location: Across the Murrumbidgee River at Wagga Wagga, NSW

Date Completed: 1895

The Hampden bridge is a wooden Allan Truss bridge which opened to traffic on 11 November

1895 . The bridge is 100.5 metres (330 ft) long with each of the 3 truss spans 33.5 metres

(110 ft) long.

Hampden Bridge was the first large overhead-braced truss bridge designed by Percy Allan.

The bridge was originally designed to be a steel-built bridge; however, the tenders were tooexpensive so timber was used as an alternative and at the time it was the longest timber

truss bridge in the World.

The bridge became outdated by a modern concrete bridge a number of years ago so the

Hampden Bridge was closed in October 1995 and left in its original state, as when it was

made redundant.
http://en.wikipedia.org/wiki/Truss_bridge#Allen_trusshttp://en.wikipedia.org/wiki/Percy_Allanhttp://en.wikipedia.org/wiki/Percy_Allanhttp://en.wikipedia.org/wiki/Truss_bridge#Allen_truss


2/12

Because of this, in 2007 the bridge suffered a major partial failure due to one of the main

timber chords failing due to extensive attack by white pocket rot where the failed area was

0.5 meters below its original profile.

In 2012, Wagga Wagga City Council voted to demolish the bridge, as the maintenance costs

associated with its preservation were too high. The issue of whether to keep the bridge or

to demolish it has divided the community of Wagga Wagga.

TIMELINE

11 November 1895 - the Hampden Bridge opens October 1995 - Just short of its 100th birthday, the Hampden Bridge is closed to

traffic when the nearby Wiradjuri Bridge opens.

16 August 2006 - the Hampden Bridge is closed to pedestrians indefinitely after theWagga Wagga City Council finds that the bridge deck has dropped 50 centimetres(20 in) after one of the trusses failed. A safety report by the Roads and TrafficAuthority states that the bridge could fall down any day due to it being in a state ofdisrepair. Wagga Wagga City Council look into ways to prop up the failed section withother options of possibly demolishing the bridge.

27 February 2008 - Wagga Wagga City Council approves $300,000 to make the bridgestructurally safe.

August 2008 - a 39-metre (128 ft) metal truss (used railway tracks to put it in place) isplaced on the failed section of the Hampden Bridge, to raise the deck for repair.

March 2012 - Wagga Wagga City Council voted to dismantle the Hampden Bridge. February 2013 - A tender is awarded to Queensland-based company, Southern Cross

Demolition, for the complete demolition of the bridge.

Project Description

Parallel chord through trusses

He based his design on the American Howe bridge but exploited the superior strength andperformance of Australian ironbark to reduce it to its barest essentials. In doing so he devised anefficient and graceful truss bridge design.

Allan truss bridges were substantially simpler than their prior allan truss designs. They used less
http://en.wikipedia.org/wiki/Pedestrianhttp://en.wikipedia.org/wiki/Roads_and_Traffic_Authorityhttp://en.wikipedia.org/wiki/Roads_and_Traffic_Authorityhttp://en.wikipedia.org/wiki/Roads_and_Traffic_Authorityhttp://en.wikipedia.org/wiki/Roads_and_Traffic_Authorityhttp://en.wikipedia.org/wiki/Pedestrian


3/12

material, were easier to repair and maintain and enjoyed long operational lives. All the timberelements were pairs of members and the joints allowed for loads to be shed onto just one memberif need be. As a result, any individual piece could be replaced easily when it became unserviceable.

The original Allan truss design had a 27.4 m (90') span and a 4.6 m (15') carriageway. It was highly

successful and bridges of this type were constructed as late as 1929. In 1895, Allan upgraded thedesign to span 33.5 m (110') with a 7.4 m (24') carriageway. He used it initially for the WaggaWagga bridge, then for other bridges throughout NSW.

The bridge is a Howe through truss with timber top and bottom chords, timber compressiondiagonals and vertical steel tension rods. It has three 33.5 m (110') truss spans and nine trestle andbeam approach spans. All the timber elements in the main spans are spaced pairs of memberswhile timber to timber joints are cast iron compression seats.

The design is efficient in materials. The sizes of members reduce towards the centre of the trussspans. The tie rods reduce from three rods in the panels closest to the supports, to a single rodeach side of the centre panel. The top and bottom chords are spliced with steel connection plates.The bottom chord splice plates incorporate vertical square ribs to transfer tension more efficientlywhile the top compression plates are simple spacing and locating plates.

Allan Truss Bridge

The Allan truss bridge is named after Percy Allan, a famous Australian architect and engineerwho designed the bridge.

His design consists of vertical and diagonal arrangements of trusses which are wereoriginally composed of steel.

Today many of the bridges based on Percy Allans design are composed of iron bark or even

timber to reduce the cost.

The Hampden Bridge in New South Wales Australia was the first bridge to be built on PercyAllans design.

Howe Truss Bridge

Howe Truss Design

Howe truss bridge is a basic design of truss bridges based on which many engineers gavemodified designs for many other famous truss bridges of the world.


4/12

It has a simple design which consists of diagonal and vertical trusses. The diagonal trussesmove upwards and slope towards the centre of the bridge. The vertical members of thetruss are in tension while the members of the diagonal truss are in compression.

This bridge was first designed by William Howe in 1840. Jay Bridge in New York and Sandy

creek covered bridge in Jefferson County, Missouri are to bridges based on Howes design.

Pratt Truss Bridge

The design of the Pratt truss is bridge is the opposite of the Howe Truss Bridge. Althoughthey too like the Howe truss have vertical and diagonal members, the major differencebetween the two is that in the Pratt Truss Bridge the Diagonal slope down towards thecentre.

This bridge was invented by Thomas and Caleb Pratt in1844. Originally this bridge was builtwith iron but not wood is also used in its making. This bridge can be extended up to 250 feettherefore it is commonly used as a railway bridge.


5/12


6/12


7/12


8/12

Legend1. Top chord, 2/450 x 150 mm2. Bottom chord, 2/330 x 175 mm3. Web, 2/435 x 170 mm

4. Web, 2/330 x 170 mm5. Web, 2/285 x 150 mm6. Cross beam, 400 x 350 mm7. Strut, 2/300 x 125 mm8. Tension rod, 65 mm 9. Cast compression seat10. Suspension plate and bolts11. Graded packer


9/12


10/12


11/12


12/12

Documents

hampden bridge for structures