Oasys GSA Documentation

# Bridge Loading Analysis Specification

As discussed in the Step-by-Step guide to Bridge Loading, there are three different ways of using the tools available for bridge loading. This specification dialogue is used to distinguish between these methods and set up the parameters for the first method.

# Bridge Design Loading Code

Unless working with UK or HK loading (HA and HB) on constant width carriageways, the code must be set to “Undefined”. Otherwise the user can select the appropriate code from the options below:

  • UK_BD37 – For HA and HB loading to the United Kingdom Design Manual for Roads and Bridges.
  • HK_SDM – For HA and HB loading to the Hong Kong Structures Design Manual.
  • UK_BD21_HB – For HA to BD21 and HB to BD37
  • UK_BD86_SV-TT – For HA to BD21 and SV-TT to BD86
  • UK_BD86_SV-Train – For HA to BD21 and SV-Train to BD86
  • UK_BD86_SV-150 – For HA to BD21 and SV-150 to BD86
  • UK_BD86_SV-100 – For HA to BD21 and SV-100 to BD86
  • UK_BD86_SV-80 – For HA to BD21 and SV-80 to BD86
  • UK_CS454_HB – For HA to CS454 and HB to BD37

Using these options where possible makes the most efficient use of the tools available for bridge loading in GSA. The SV loading types are an approximate implementation of the requirements of BD86 requirements. Intensity of SV vehicle loading is adjusted to compensate for the different load factors (1.1 for vehicles, 1.3 for associated lane loading). SV loading is applied in a similar way to HB loading to BD37, with HA loading applied over the full width of lanes, not on 2.5m widths within lanes as required by BD86/BD21; note that this is unconservative if there is little or no transverse distribution in the bridge. All HA loading is factored by 0.91 (equivalent to Heavy Traffic / Poor Surface to BD21).

# UK/HK Loading

To allow for different load factors in different combinations, the user can specify one or more of the following:

  • ULS Comb1: for ULS Load Combination 1 (dead and live load only)
  • ULS Comb3: for other ULS load combinations (dead, live and temperature or dead, live and wind)
  • SLS Comb1: for SLS Load Combination 1

Using these options where possible makes the most efficient use of the tools available for bridge loading in GSA. The SV loading types are an approximate implementation of the requirements of BD86 requirements. Intensity of SV vehicle loading is adjusted to compensate for the different load factors (1.1 for vehicles, 1.3 for associated lane loading). SV loading is applied in a similar way to HB loading to BD37.  HA loading applied over the full width of lanes, not on 2.5m widths within lanes as required by BD86/BD21/CS454; note that this is unconservative if there is little or no transverse distribution in the bridge. All HA loading is factored by 0.91 (equivalent to Heavy Traffic / Poor Surface to BD21/CS454).

Note: As the number of analysis cases in the bridge analysis task depends on the bridge specification, the editing of bridge analysis specification will be disabled if there is a bridge analysis task.

In addition for CS454:

  • Single axle consideration (CS454 Clause 5.17(2)) is not included.
  • A pedestrian live load factor of 0.8 from CS454 Table 5.32b is be adopted. Elements supporting footways only, will need to be run with path loading to allow factor of 1.0
  • A pedestrian width factor of 1*width (the value of 1 from Table 5.32b is adopted).

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