HB loading(abnormal vehicle unit load)
In 1945 the HB loading concept was introduced by British standards. HB loading represents the abnormal vehicle unit load such as exceptional industrial loads (e.g. electrical transformers, generators, pressure vessels, machine presses, etc.). Figure 1 depicts one unit of HB loading. load comprises of 4 axles. each axle composed of 4 wheels spaced equally. rear axles are spaced by 1.8m. similarly, front axles are spaced by 1.8m. spacing between the rear and front axles can vary (6,11,16,21 or 26m). whichever dimension that will cause the most severe effect on a member under consideration shall be selected.
the number of units of HB loading depends on the class of roads:
- motorway and trunks roads required 45 units. figure no:2 showing 45 units loads of HB loading (HB45).
- principal road 37.5 units.
- public roads 30 units.