The King Street Bridge was designed in 1959 by Hardcastle and Richards, consulting engineers for the main contractor, Utah Australia for the Country Roads Board, and constructed over the next two years, being opened on 12 April 1961.
It is of a welded, steel girder concrete deck cantilever-suspended span construction with suspended spans up to approximately 100 feet (30 m) long.

The King Street Bridge carries King Street over the Yarra River.
The bridge continues south as an elevated viaduct, with the Crown Casino built around it in later years.

Soon after completion, on 10 July 1962, one span collapsed under the weight of a 47-ton semi-trailer, though the weight was within the bridge limits.

The following, excepting Reconstruction, is taken from the report of the Royal Commission.

Short history
Sep 1956.
  Design and construct tenders called by the Country Roads Board of Victoria (CRB) as the       Constructing Authority.

May 1957   Tenders awarded.

Sep 1957    Work started.

Apr 1961     Open to traffic.

Oct 1961     Bridge handed over to Melbourne & Metropolitan Board of Works (MMBW) as a     metropolitan highway.

Jul 1962      Bridge collapsed.

Sep 1962
to                Royal Commission into the failure of Kings Bridge.

Aug 1963
Participants for Construction
CRB                   Constructing Authority and Contract Principal.

UTAH Aust Ltd   Principal Contractor.

J&W                   Johns & Waygood.
  Subcontractor to Utah for fabrication, erection and painting of 		girders.

H&R                   Hardcastle and Richards, consulting Engineers.
Subcontractor to Utah for 			detailed design of superstructure.

BHP                   Broken Hill Propriety Ltd. for supply of steel.

Design
The superstructure design by H&R incorporated standard design details for girders and cover plates as was common at the time for mild steel construction.
CRB had allowed in the tender the use of high tensile steel to British Standard BS 968:1941.
H&R chose to use this steel to reduce weight, so economising on the cost of the foundations.
Design and construction of the foundations was undertaken by UTAH.

Included in the CRB tender documents were comprehensive specifications for fabrication in high tensile steel to be read in conjunction with and additional to those of BS 968 -1941.

Neither UTAH nor J&W ever really appreciated the differences that high tensile steel presented in its fabrication, particularly with regards to welding.
Therein started the road to failure.

Material supply
J&W, when placing their order for steel from BHP, failed to require  additional tests as per the CRB specifications.
As a result, BHP only supplied ladle analyses.
BHP even stated to J&W at some stage that Izod tests for ductility as per the CRB specifications were useless.

Not all tensile and Izod tests for different plate thicknesses were carried out.

Steel supplied by BHP was generally very close to the maximum tolerances regarding chemical composition.
It was later revealed  that the chemical composition of plates sometimes exceeded specification even when ladle analysis was within specification.
BHP also did not appreciate the welding requirements for high tensile steel and even advised J&W on occasion that even when the chemical composition shown by ladle analysis exceeded specification, the steel was still weldable.
Brittleness  was of prime importance and under test, some samples did not even show a yield point.

Cover plates & Welding
H&R placed the transverse welded ends of cover plates of tension flanges in regions of low stress as permitted by the specifications.
Had proper consideration  been given during fabrication to weld preparation, the failure of the bridge may not have occurred.
The greatest oversight appeared to be the lack of, or insufficient, preheat around the weld area to limit the intensity of residual stresses in the heat affected zone.
In these circumstances, brittle fracture was almost guaranteed.
In fact, all the cracks occurred in the HAZ of the plate material.

Izod tests for plate and welds were specificied.
Many Izod tests, parti
The King Street Bridge was designed in 1959 by Hardcastle and Richards, consulting engineers for the main contractor, Utah Australia for the Country Roads Board, and constructed over the next two years, being opened on 12 April 1961. It is of a welded, steel girder concrete deck cantilever-suspended span construction with suspended spans up to approximately 100 feet (30 m) long.
The King Street Bridge carries King Street over the Yarra River. The bridge continues south as an elevated viaduct, with the Crown Casino built around it in later years.
Soon after completion, on 10 July 1962, one span collapsed under the weight of a 47-ton semi-trailer, though the weight was within the bridge limits.
The following, excepting Reconstruction, is taken from the report of the Royal Commission.
Short history
Sep 1956.   Design and construct tenders called by the Country Roads Board of Victoria (CRB) as the       Constructing Authority.
May 1957   Tenders awarded.
Sep 1957    Work started.
Apr 1961     Open to traffic.
Oct 1961     Bridge handed over to Melbourne & Metropolitan Board of Works (MMBW) as a     metropolitan highway.
Jul 1962      Bridge collapsed.
Sep 1962
to                Royal Commission into the failure of Kings Bridge.
Aug 1963
Participants for Construction
CRB                   Constructing Authority and Contract Principal.
UTAH Aust Ltd   Principal Contractor.
J&W                   Johns & Waygood.  Subcontractor to Utah for fabrication, erection and painting of 		girders.
H&R                   Hardcastle and Richards, consulting Engineers. Subcontractor to Utah for 			detailed design of superstructure.
BHP                   Broken Hill Propriety Ltd. for supply of steel.
Design
The superstructure design by H&R incorporated standard design details for girders and cover plates as was common at the time for mild steel construction. CRB had allowed in the tender the use of high tensile steel to British Standard BS 968:1941. H&R chose to use this steel to reduce weight, so economising on the cost of the foundations. Design and construction of the foundations was undertaken by UTAH.
Included in the CRB tender documents were comprehensive specifications for fabrication in high tensile steel to be read in conjunction with and additional to those of BS 968 -1941.
Neither UTAH nor J&W ever really appreciated the differences that high tensile steel presented in its fabrication, particularly with regards to welding. Therein started the road to failure.
Material supply
J&W, when placing their order for steel from BHP, failed to require  additional tests as per the CRB specifications. As a result, BHP only supplied ladle analyses. BHP even stated to J&W at some stage that Izod tests for ductility as per the CRB specifications were useless.
Not all tensile and Izod tests for different plate thicknesses were carried out.
Steel supplied by BHP was generally very close to the maximum tolerances regarding chemical composition. It was later revealed  that the chemical composition of plates sometimes exceeded specification even when ladle analysis was within specification. BHP also did not appreciate the welding requirements for high tensile steel and even advised J&W on occasion that even when the chemical composition shown by ladle analysis exceeded specification, the steel was still weldable. Brittleness  was of prime importance and under test, some samples did not even show a yield point.
Cover plates & Welding
H&R placed the transverse welded ends of cover plates of tension flanges in regions of low stress as permitted by the specifications. Had proper consideration  been given during fabrication to weld preparation, the failure of the bridge may not have occurred. The greatest oversight appeared to be the lack of, or insufficient, preheat around the weld area to limit the intensity of residual stresses in the heat affected zone. In these circumstances, brittle fracture was almost guaranteed. In fact, all the cracks occurred in the HAZ of the plate material.
Izod tests for plate and welds were specificied. Many Izod tests, parti
King Street Bridge (Melbourne)