Single shear vs. double shear for nails in lateral loading

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1952
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Virginia Polytechnic Institute
Abstract

Tests were conducted on three-member southern pine joints to determine (1) the relationship of the lateral load-carrying capacity of nails in single and double shear, and (2) to develop a basis for structural design data for laterally loaded nails in double shear applicable whenever deformation is a governing factor, such as in joints of trussed rafters.

The test loads at or near proportional limit show that low-carbon-steel plain-shank and helically threaded Screwtite nails loaded in double shear carry twice the single-shear loads; while hardened high-carbon-steel plain-shank and Screwtite nails loaded in double shear carry considerably less than twice the single-shear loads. If these relationships between single-shear and double-shear loads are to be valid, the nail must be optimum diameter tor the joint.

Structural design data as based on test loads at or near proportional limit for laterally loaded low-carbon-steel plain-shank nails in single and double shear are applicable to low-carbon-steel Screwtite nails and to same-length, smaller-diameter, hardened high-carbon-steel plain-shank and Screwtite nails. This finding, however, is not valid if consideration is to be given to the load-carrying capacity beyond proportional limit and at ultimate, to the influence or exposure on nail-holding power, and to certain advantage resulting from the use of threaded-shank as well as hardened nails.

Design data as advanced in the National Design Specification for low-carbon-steel plain-shank nails in single shear are verified within their scope. Additional information is presented on the performance or plain-shank nails, Screwtite nails, and Stronghold Screwnails under given conditions, on the effects or pre-boring and clinching, and on the efficiency or toothed-ring Burrlock fasteners as reinforcement for nailed lumber joints.

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