live load distibution and group girders

[foreng]

Looking for some advice on how to calculate the live load distribution for a set of grouped girders.

Single lane bridge, 4.3 m deck width, 4 glulam girders, spaced in pairs of 2 @ 3.05 m apart. The two girders in the group are spaced 600 mm apart. Should I treat the pair as a one unit and distribute the load at the centre on the pair? This is for the evaluation of and existing structure approx 30m long.

 

[Ron]

If the two are "tied" laterally so that torsion is eliminated, yes you can consider them as acting together with the load applied and split between them.

 

[foreng]

Yes they are tied laterally with diaphragms every 4m.

Thanks