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3.2.1 Design loads and construction sequence

The design loads and any construction sequence limitations shall be shown on the drawings and specifications for all bridges in accordance with AS 5100.

3.2.2 Design traffic loads for new bridges

a) The design traffic live loads for new bridges are SM1600, W80, A160 and HLP 400 in accordance with AS 5100. Refer to Section 6 “Additional Requirements to AS 5100 Bridge Code” for specific design requirement for placement of HLP Loads.

b) These design loads apply to all new road bridges and new culverts on declared main roads, except in unusual circumstances that have been accepted in writing by the Deputy Chief Engineer (Structures).

c) These conditions shall also apply to any overbridge across a declared main road which is likely to be travelled by a HLP which cannot fit beneath it and is likely to go across the overbridge.

3.2.3 Design traffic loads for widening/strengthening an existing bridge or culvert

The cost of widening/strengthening should be compared against the cost of a bridge replacement. If a new bridge to current loads is more economic, a new bridge should be constructed.

The design lane excluding HLP shall comply with AS 5100. HLP position shall comply with Clause 6 (Additional requirements to AS 5100 Bridge Code) of this document.

Other loading design parameters shall be as follows:

• Load factor for dead loads and superimposed load As per AS 5100

• Ultimate load factor for traffic loads (excluding HLP) 2.0

• Ultimate load factor for HLP As per AS 5100 for speed

• Dynamic load allowance:

a) for cranes and AB triple, AAB quad, HML semi, at speed 0.4, at speed

b) Vehicles specified in AS 5100 as per AS 5100 at speed

c) Vehicles at crawl Zero

• Accompanying lane factors As per AS 5100

Chapter 3: Bridge functional requirements

3.2.3.1 Design traffic loads for simply support spans of less than 50m

Design traffic loads for simply support spans of less than 50 m shall be as shown in the Table 3.2.3.1. Figure 3.2.3.1 shows the details of 6 axle semi, AB Triple and AAB Quad.

Chapter 3: Bridge functional requirements

Table 3.2.3.1 - Design traffic loads for simply supported spans of less than 50 m

Road classification/name Design vehicle Accompanying vehicle

Any bridge constructed since 2004

SM 1600 and HLP 400 to Transport and Main Roads Bridges and Other Structures Design Criteria, or 48 t or 79.5 t crane plus coexisting vehicle to AS 5100

Any bridge constructed between 1976 and 2004

Design criteria will be the greater of 1. Original design load, or

2. Load specified below. Minimum for Gateway

Arterial, Logan Motorway, Ipswich Motorway, Pacific Motorway (excluding Captain Cook Bridge to Gateway Motorway), Western Corridor, Warrego Highway east of

Toowoomba, Bruce Highway, Capricorn

Highway, Dawson Highway and all Port Access Roads)

• Multiple T44's with a 3 m (stationary) or 6 m (moving)** minimum headway between vehicles, located for maximum load effects, or

• HML AB triples T1 road train (4.4 m axle group spacing), or

• HML AAB quad T2 road trains (4.4 m axle group spacing) or,

• 48 t crane in lane at speed, or

• 79.5 t crane in lane at speed.

• HML AB triples T1 road train (4.4m axle group spacing), or

• HML AAB quad T2 road trains (4.4m axle group spacing)

• HLP 320 (+/- 1.0 m centre of 2 marked lanes) at speed

For HLP vehicles only, accompanying vehicle only used in other lanes when 3+ design lanes exist.

Half of (HML AB triples T1 road train (4.4m axle group spacing), or HML AAB quad T2 road trains (4.4 m axle group spacing))

Minimum for National Highways, B double routes and Type 1 road train routes (Excluding Gateway Arterial, Logan Motorway, Ipswich Motorway, Pacific Motorway, Western Corridor, Warrego Highway east of

Toowoomba, Bruce Highway, Capricorn

Highway, Dawson Highway and all Port Access Roads)

• Multiple T44's with a 3 m (stationary) or 6 m (moving)** minimum headway between vehicles, located for maximum load effects, or

• HML AB triples T1 road train (4.4 m axle group spacing), or

• HML AAB quad T2 road trains (4.4 m axle group spacing) or,

• 48 t crane in lane at speed.

• HLP 280* (+/- 1.0 m centre of 2 marked lanes) at speed

• HML AB triples T1 road train (4.4 m axle group spacing), or

• HML AAB quad road trains (4.4 m axle group spacing)

For HLP vehicles only, accompanying vehicle only used in other lanes when 3+ design lanes exist.

Half of (HML AB triples T1 road train (4.4 m axle group spacing), or HML AAB quad T2 road trains (4.4 m axle group spacing))

Chapter 3: Bridge functional requirements

Road classification/name Design vehicle Accompanying vehicle

Minimum for Pacific Motorway (Captain Cook Bridge to Gateway Motorway)

• Multiple T44's with a 3 m (stationary) or 6 m (moving)** minimum headway between vehicles, located for maximum load effects, or

• 48 t crane in lane at speed,

• 48 t crane at crawl on centreline.

Multiple T44's with a 3 m (stationary) or 6 m (moving)** minimum headway between vehicles, located for maximum load effects

Minimum for Type 2 Road train routes and any other road not specified above

• HML AB triples T1 road train (4.4 m axle group spacing), or

• HML AAB quad T2 road trains (4.4m axle group spacing) or,

• 48 t crane at crawl on centreline.

Bridges greater than 30 m long

HML AAB quad T2 road trains (4.4 m axle group spacing)

Bridges less than 30 m long

Two HML semitrailers with a 4 m minimum headway between vehicles, located for maximum load effects.

• HLP 240* (+/- 1.0m centre of 2 design lanes) at crawl Nil

* Similar geometry to HLP 320 with axle weight proportionally reduced. ** Distance between axles of the leading and following vehicles.

Chapter 3: Bridge functional requirements

3.2.3.2 Design traffic loads for simply supported spans over 50 m and continuous spans

Special criteria apply – refer to Deputy Chief Engineer (Structures) for criteria of each bridge. Design must consider worst effect due to 6 axle semi, AB triple or AAB quad and design vehicles.

Additional criteria:

1. Maximum spacing between axle groups can vary between 4.4 m and 6.0 m for continuous bridges to create the worst load effect.

2. Minimum spacing between following vehicles is 3.0 m for stationary and 6.0 m when moving. Maximum spacing is the dimension to create the worst load effect considering pattern loading of spans.

3.2.3.3 Design traffic loads for local authority bridges and culverts

The load rating of a Local Authority bridge or Local Authority culvert shall be as specified by the Local Authority but not less than H20-S16.

3.2.4 Design traffic loads for damaged bridges

For bridges damaged in service, the damaged section shall be reinstated to the design load existing prior to the vehicle impact. If the bridge is required to be replaced, the new superstructure shall be designed to the criteria for new bridges if possible. If this cannot be obtained, the design loading shall not be less than T44, A14 and HLP 320.

3.2.5 Heavy load platforms

a) Heavy Load Platforms (HLP) represent actual configuration of vehicles that travel on the road network, not design simplifications.

b) On road projects associated with major infrastructure (mines, power stations and so on), there may be a requirement for a heavier HLP in bridge design. Designers shall consult the relevant authorities before detailed design commences. Typically, a heavy load platform can “safely” carry much higher loads (up to 50 tonne/axle) than normally allowed on bridges (25 ton/axle).

3.2.6 Abnormal loads

Any requirements for abnormal loads shall be defined in accordance with Section 7 (Item S2).

3.2.7 Special conditions for footbridges

For the design of a stand alone footbridge, lateral loads (AS 5100.2, Clause 9) are a critical load case. For new structures the minimum lateral load is 500 kN.

For footbridges over waterways and navigable channels, ‘ship’/navigational vessel impact shall be taken into account. AS 5100 does not address ship impact, however, Transport and Main Roads Design Criteria for Bridges and Other Structures covers this issue in Section 7.