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V.4.2.3.1Amendment No. V-l/91 (Jan.)TABLE 4.2.1WIND VELOCITIESLOCATIONRETURNPERIOD(Years)MAXIMUM HOURLYWIND VELOCITYKnotsm/sMAXIMUM GUSTVELOCITYKnotsm/sWaglan501002008594103444853137151165717885RoyalObservatory501002008087954145501331461586875814.2.3.1 Bridges with spans less than 100mTable 4.2.2 gives values of dynamic pressure headto be used for design proposes in Hong Kong for bridges whosemaximum span is less than 100m. The values given for"sheltered locations" were in general use before the need forhigher values at exposed locations was appreciated. As theprobability is low of much traffic being present at gustvelocities exceeding 44 m/sec, the corresponding dynamicpressure head of 1.2 kN/m 2 may be used for the loaded stateat all locations.The values of dynamic pressure head to be used forthe unloaded state at locations of intermediate exposure areto be interpolated, by the use of engineering judgement,between the extremes given for sheltered and exposedlocations in Table 4.2.2. To aid designers in choosingsuitable values, descriptions and examples of typicallocations are given in Table 4.2.3.Values of dynamic pressure head derived fromTable 4.2.2 should be used to determine the nominaltransverse, longitudinal and vertical wind loads describedin clauses 5.3.3, 5.3.4 and 5.3.5 of BS 5400 : Part 2.In all other respects, the provisions ofsection 5,3 of BS 5400 : Part 2 regarding wind load shouldbe followed for structures with spans of 100m and less.4.2.3.2 Bridges with any span greater than 100mFor bridges with any span greater than 100m, therequirements of Appendix 4.2.3 should be used.