Number of lane in curved Ramp with varying width - AASHTO LRFD 1

[Nayan67]

Hello everyone,

I am analyzing a curved ramp with three spans (36m, 45m, and 30m). The first two spans have a carriage width of more than 11.0 meters. However, between the second and third spans, there is a portion where the carriage width is less than 10.5 meters. In this regard, how many lanes should there be? Should I use three lanes (since 11/3.65 > 3.0) in the portions where the carriage width is greater than 11.0 meters and then reduce to two lanes where the ratio of carriage width to 3.65 is less than 3.0?

 

[BridgeSmith]

I would say that since it's not possible to have 3 lanes all the way across the bridge, you could analyze it as a 2 lane bridge.

The only place where I think it would matter is for the total live load on the substructures, so if you wanted to consider 3 lanes for that calculation on the substructures supporting the spans where it's wide enough for 3 lanes, you could. With the Rigid Override considered, the scenario with 3 lanes loaded is unlikely to produce a critical load combination, though.

 

[Nayan67]

BridgeSmith, Thank you so much for your insights.