Evaluation of screws used in laminated veneer lumber rocking connections

D. M. Carradine, M. P. Newcombe and A. H. Buchanan

There is a large body of research currently underway in New Zealand investigating the behaviour and design of multistorey and long-span structures utilizing laminated veneer lumber (LVL) as beam, column and wall components. Screws have significant potential for use as fasteners for a myriad of connections throughout these buildings. There is currently a lack of data on the behaviour of screws when used with LVL. In many cases screws are installed parallel to the laminations (and glue-lines) and subjected to withdrawal loading, so it is necessary to determine appropriate configurations of screws that can be safely used in these situations. Some systems also place high structural demands on corbels to support floor units and gravity beams. Monotonic testing on double shear screwed connections in LVL has been performed on specimens with varying screw configurations, LVL thickness, member depth and corbel configurations. Direct withdrawal tests of screws installed into the edge grain of LVL, parallel to the glue lines were conducted using varying screw penetration depth, screw spacing and numbers of screws. Comparisons are drawn between existing standards for determining screw connection capacity typically used for solid timber and glue laminated material and the capacities of the screwed connections in LVL. Recommendations are made for calculating LVL connection strength using screws as well as the limitations of existing design code predictions when using screws installed parallel to glue lines in LVL.

TDJ 19/2

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