Sidewalk live load

[broekie]

Just curious how other engineers handle sidewalk live load on a typical I-grider bridge. Seems to me that this could be handled a couple of different ways:

1. Distribute live load evenly among all the beams with no reduction of load factors.

2. Distribute the live load among exterior beam(s) and use the lower load factor allowed by AASHTO for the combined sidewalk/vehicular live load.

My question for method #2 is how many beams to distribute the sidewalk live load to. Certainly more than just the exterior beam would carry sidewalk live load, especially since by code the sidewalk dead load can be distributed among all the beams.

I've always used method #1, but I was just curious what others have done. Thanks.

 

[crossframe]

No. 1 makes sense, since the load is applied after the bridge deck is placed (like SDL), and I've done this in the past. At other times, I've distributed the load evenly to fewer (usually 3) beams. I've gone to more beams if it's a very wide sidewalk (like the curb line near the second interior beam) or other unusual geometries.

Massachusetts specifies 60% of sidewalk LL to exterior beam, 40% to all the interior beams, and if a sidewalk spans over two or more beams, the 60% is distributed evenly among those beams, and 40% to the remaining beams.

 

[bridgebuster]

No 1 is how I usually do it also.

I forgot about Massachusetts. I designed some bridges there in the early/mid 80's.