Ship Ladder Loading
Ship Ladder Loading
(OP)
thread507-337483: Fixed ladder and ships ladder live loads
I received a submittal for a ship ladder which services a mechanical room in a stadium. Per ASCE 7-10 §4.5.4:
"The minimum design live load on fixed ladders
with rungs shall be a single concentrated load of 300
lb (1.33 kN), and shall be applied at any point to
produce the maximum load effect on the element
being considered. The number and position of
additional concentrated live load units shall be a
minimum of 1 unit of 300 lb (1.33 kN) for every 10 ft
(3.05 m) of ladder height.
In the submittal the speciality engineer has designed for a 300 lb point load but he has also placed this load at an 18" eccentricity from the rung. He is using the moment from this eccentricity to design the stringers. Is this required?I understand that the center of gravity of whoever is on the rung will be at some distance away from the center line however his feet will always be on the rungs, thus no eccentricity.
I received a submittal for a ship ladder which services a mechanical room in a stadium. Per ASCE 7-10 §4.5.4:
"The minimum design live load on fixed ladders
with rungs shall be a single concentrated load of 300
lb (1.33 kN), and shall be applied at any point to
produce the maximum load effect on the element
being considered. The number and position of
additional concentrated live load units shall be a
minimum of 1 unit of 300 lb (1.33 kN) for every 10 ft
(3.05 m) of ladder height.
In the submittal the speciality engineer has designed for a 300 lb point load but he has also placed this load at an 18" eccentricity from the rung. He is using the moment from this eccentricity to design the stringers. Is this required?I understand that the center of gravity of whoever is on the rung will be at some distance away from the center line however his feet will always be on the rungs, thus no eccentricity.






RE: Ship Ladder Loading
RE: Ship Ladder Loading
Think about it for a moment - if the center of mass of the person is 18" away from the rung, there is both the gravity load (vertical) on the rung (300#) AND a lateral force due to the fact that his/her body is 18" away from the ladder. Thus there is an eccentricity.
If you've ever climbed a ladder with a weak rung you would see that the rung deflects both downward as well as away from one's body.
I feel the approach is correct.
Ralph
Structures Consulting
Northeast USA
RE: Ship Ladder Loading
RE: Ship Ladder Loading
There is no way for a single point load passing through a member to apply a moment to the member. I think the whole point of the standard being written this way is so that we don't have to imagine the infinite number of ways that the worker might be moving or postured.
RE: Ship Ladder Loading
RE: Ship Ladder Loading