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Re: railing design
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- Subject: Re: railing design
- From: Charles Greenlaw <cgreenlaw(--nospam--at)speedlink.com>
- Date: Mon, 15 Feb 1999 16:43:22 -0800
Presuming from the Q and A so far that the verticals are steel, and all alike, and cantilever up from a moment connection at the stair stringer to a steel flat bar at their top ends, to which all the verticals connect rigidly, you have a classic "beam on elastic foundation". The code horizontal load of 200 lbs. is a point load (isn't it) acting horizontally on the top rail "beam", which spans horizontally. The resistance is the whole array of verticals, each of which supports the beam with a springy resistance, the amount of which depends on the deflection imposed. The horizontal stiffness of the top rail, with respect to the stiffness of each vertical against horizontal load at its top end, is the basis of analysis. Timoshenko presents a complete solution in his texts on Strength of Materials, Part II, dating from 1930 and still in use at least into the 1960's. His solution also covers the case where the applied load is distributed over a certain length of the "beam", or there are multiple point loads. There are formulas, curves, and tables. If an approximate solution is adequate, it could be done by trial and error as Richard Lewis suggested, keeping in mind the basic principle. There are code limits for stairway handrail dimensions that relate to a person being able to grasp and hang on. Lateral stiffness wants to be enough that subjective confidence in the sturdiness of the thing is not impaired. Charles O. Greenlaw, SE Sacramento CA ******************************************** Original question: >i have a handrail that has 1/2" X 1/2" verticals at 4" o.c. with a >nominal flat stock top horizontal. in applying the code required 200 # >horizontal load what effective width is allowed. another words how many >verticals can contribute? > >another question is, what is the codefied deflection criteria?
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