Evaluation of screws used in laminated veneer lumber rocking connections

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