huangyhg

handrail bracket attachment to stud wall
i am looking an approach to provide a calculation for the safe design of a typical handrail bracket to a stud wall. wood blocking provided behind the gwb is required for lag bolts used to connect the bracket.
here are a few problems i have encouter while trying to solve this problem.
1. one method which has been approved in the past is to estimate the bearing strength of gwb based on the number of fasteners required by code to secure a piece of gwb to the wall. the estimate is 800 psi, allowing for the safe bearing of the bracket directly on the gwb. data from usg shows that gwb actually has a bearing capacity of 400 psi. this strength when used with a uniform or triangluar pressure base plate design results in a tension too high for the lag bolt.
2. most bracket manufacturers provide a stamped metal filler so that brackets don't have to bear on plaster. the fitting has a small edge with a gauge thickness. this does not provide adequate bearing area on spf wood blocking.
3. a 5/8" plywood filler has less bearing capacity than spf and is not adequate.
4. an spf filler would have to be cut to size and concealed in the field.
bracket manufacturers, gwb manufacturers & naamm all provide suggested details for this connection, but refuse to provide any engineer data for these design. short of conducting a physical test are there any other methods for this design?
thanks.
in california the code would require that the handrail resist a 200# load applied anywhere along the handrail in any direction. to comply with this requirement you must provide a very solid surface to mount the hand rail to.
the handrail manufactures, probably don't provide any engineering data because requirements very from state to state. also in the past i've found that many standard details out there will not meet code.
if you are writting the specifications for the project require the handrail supplier to supply certfied calculations with details of mounting methods to meet the code requirements.
i am the handrail supplier to supply certfied calculations to resist a force of 200 lbf per the ibc.
bump
seems like a bad approach that if you can't get a calculations to work then it should be specified for someone else to design. just a thought, could a heavy gauge steel studs be used with steel angles provided between the studs which you could anchor to. a thru bolt would need to be used instead of the lag bolts. i understand the frustration. most handrail system out there do not meet code.

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