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 BS5400:Pt2
LOADING
CLAUSE No
SUBJECT
Type HA loading (Example)
Problem:
How do you work out the HA loading and bending moment for a bridge deck ?
Example:
Carriageway = 7.3m wide
Deck span = 34m (centre to centre of bearings for a simply supported single span)
Design for a metre width of deck :
Cl. 3.2.9.3.1.
Number of notional lanes = 2
Notional lane width = 7.3/2 = 3.65m
Cl. 6.2.1.
Loaded length = 34m
W = 336(1/L)0.67 kN/m (per notional lane)
W = 31.6 kN/m (per notional lane)
Cl. 6.2.2.
Knife Edge Load = 120 kN (per notional lane)
Cl. 6.4.1.1.
α2 = 0.0137[bL(40-L)+3.65(L-20)]
α2 = 0.0137[3.65(40-34.0)+3.65(34.0-20)] = 1.0
Note: For loaded lengths less than 20m the load is proportioned to a standard lane width of 3.65m, i.e. 0.274bL = bL/3.65.
For a metre width of deck :
W = (31.6 x 1.0)/3.65 = 8.66 kN/m
KEL = (120 x 1.0)/3.65 = 32.88 kN
Cl. 6.2.7.
γfL = 1.50 (Ultimate limit state - combination 1)
Design HA loading for a metre width of deck :
W = 1.5 x 8.66 = 12.99 kN/m
KEL = 1.5 x 32.88 = 49.32 kN
Maximum mid span Bending Moment with KEL at mid span = Mult
Mult = (12.99 x 342)/8 + (49.32 x 34)/4
Mult = 1877 + 419 = 2300 kNm
Note: Use of γf3
BS 5400 Pt.3 & Pt.5 - γf3 is used with the design strength so Mult = 2300 kNm.
BS 5400 Pt.4 - γf3 is used with the load effect so Mult = 1.1 x 2300 = 2530 kNm.

Last Updated : 18/04/2008
For more information :
Email: david@childs-ceng.demon.co.uk
