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Abstract
Hand railings are a part of everyday life. These railings need to be designed such that they do not fail. How can the live loads from people be approximated? The International Building Code [IBC] attempts to answer this question by requiring the railing to resist either a 200 lb. lateral point load or a 50 plf lateral load, whichever is the worst case based on post spacing, be resisted by the railing by placing the load at the top rail at a minimum of 42 in. from the ground. If the posts are spaced at four ft. the load from the point load will be the same as the 50 plf load.
Railings are connected a variety of ways into the base material whether that is cast-in-place, post-installed or welded. The specific connection that was chosen to test was a 1 ¼ in. nominal diameter schedule 80 pipe, cast-in-place into concrete. The embedment depth, edge distance and slab thickness were varied. The parameters chosen mimic standard dimensions used in practice.
Based on ACI 318-14 provisions, a theoretical capacity is determined to be compared to the actual tested capacity. Due to the applied lateral load at an eccentricity of 42 in., a moment is inherently applied into the concrete. The code is not clear how to account for the moment in the concrete when the ACI code provision assumes the connection to only see shear. The paper explores whether simply uncoupling the moment is a sufficient assumption to make and how the results compare to what previous research found. The testing described in this paper was also intended to verify whether the parameters for each connection satisfy the strength requirement laid out in IBC for railings and whether ACI 318-14 can accurately predict the concrete breakout strength of embedded pipe when subjected to lateral loads.
The testing methods included casting vertical pipe pieces with varying parameters into concrete pieces. The concrete pieces are turned such that the pipes are horizontal and placed into a wooden frame to prevent rotation. Weights are hung in a wooden basket at 42 in. until either concrete breakout failure occurs, or the pipe yielded until the basket weights touched the ground. The test data include 36 total tests with varying parameters to mimic standard dimension used in practice.
From the test data, the three lowest tests failed at 260 lb., 295 lb. and 295 lb. All three of these tests had the same parameters, corner test, Ca1 of three in. [distance to edge parallel to shear load], Ca2 of three in. [distance to edge perpendicular to shear load], and hef of three in. [embedment depth of post]. The results as a whole, matched ACI 318-14 within a percent difference of 2.13%. Due to the close match of results, the design assumption of uncoupling the moment to get the shear force in the concrete is valid and that designs used in practice are valid to resist the minimum load specified by IBC.