Fastener system for structural members

A fastener system adapted to secure abutting, structural members having aligned openings of substantially equal diameter passing therethrough comprising in combination:

• a sleeve having an external diameter substantially equal to the diameter of said aligned structural member openings and a length not less than the aggregate length of said aligned openings of said abutting structural members;
• and
• a fastener element and mandrel element integrally connected end to end in coaxial alignment by a neck of substantially less thickness to thereby constitute a frangible connection,
• said mandrel element being formed by a constant diameter portion at the end thereof remote from said neck which conforms in diameter and shape to the interior of said sleeve and is at least as long as said aligned openings of said abutting structural members whereby said sleeve is adapted to be disposed on and around said constant diameter portion with substantially no applied force and a tapered diameter portion between said neck and said constant diameter portion with the maximum transverse dimention thereof located adjacent said neck and equal to the interior sleeve diameter plus about 3.5 percent to 6.5 percent of said interior sleeve diameter, and
• said fastener element being formed by a shank having a length approximately equal to that of said aligned and contiguous structural member openings and a diameter substantially equal to that of said sleeve interior plus about from 2 percent to 5 percent of said sleeve interior diameter, a head on the end of said shank remote from said neck shaped and sized to conform with and abut the opening defining surface in the adjacent structural member and a tail end adjacent said neck including a retainer element adapted to act in opposition to said head.