The ratio of the built-up column compression capacity to that of a solid column is defined as efficiency (1). The capacity of a built-up column can be expressed as a percentage of the strength of a solid column of the same dimensions and made with material of the same grade and species. These three classes of columns have differing load capacities. The design of built-up columns is different from the design of solid columns. If built-up members have spacer blocks between the members, they create a spaced column. Mechanically laminated built-up columns are formed by fastening two or more members with bolts, nails or screws. Solid columns are single members or individual members glued together to act as one solid member. Instead, installers can now install all the screws from one side of the built-up column, which provides time and cost savings.Ĭolumns can be classified into solid columns, built-up columns and spaced columns. With these screws, there’s no longer a need to nail from both sides of the column, or to use not-so-common 30d nails as specified in the NDS, or to pre-drill for bolts. Simpson Strong-Tie evaluated Strong-Drive® SDW Truss-Ply screws for attaching multiple laminations with easier installation methods. Designing built-up columns? Now there’s a way to mechanically laminate multiple 2x members to meet the specifications in the National Design Specifications for wood.
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