Corrugated sheet metal structural members

Claim 1

AN ELONGATED AND SUBSTANTIALLY STRAIGHT STRUCTURAL MEMBER FORMED FROM A THIN METAL SHEET TO PROVIDE A WEB PORTION AND AN OUTSTANDING FLANGE PORTION, ONE OF SAID PORTIONS BEING OF SUBSTANTIALLY UNIFORM WALL THICKNESS AND CORRUGATED LONGITUDINALLY TO PRODUCE INNER AND OUTER OPPOSITE SURFACES OF VARYING CONTOUR, SAID OUTER SURFACE BEING ADAPTED TO BE ENGAGED BY THE POINT OF A SCREW AND INCLUDING A PLURALITY OF LATERALLY SPACED AND LONGITUDINALLY EXTENDING V-SHAPED GROOVES SEVERALLY FORMING AN INCLUDED ANGLE OF ABOUT 90* AND SEPARATED BY FIRST SUBSTANTIALLY FLAT SECTIONS, SAID INNER SURFACE INCLUDING A PLURALITY OF LATERALLY SPACED AND LONGITUDINALLY EXTENDING ARCUATE SALIENTS SEVERALLY OPPOSITE SAID GROOVES AND SEPARATED BY SECOND SUBSTANTIALLY FLAT SECTIONS SEVERALLY OPPOSITE AND NARROWER THAN SAID FIRST SUBSTANTIALLY FLAT SECTIONS, SAID GROOVES HAVING A WIDTH OF ABOUT TWICE THEIR DEPTH BECAUSE OF SAID INCLUDED ANGLE, A LATERAL SPACING, CENTER TO CENTER RANGING FROM A MINIMUM SUFFICIENTLY GREATER THAN SAID WIDTH TO PERMIT FORMATION OF SAID FIRST SUBSTANTIALLY FLAT SECTIONS, TO A MAXIMUM OF ABOUT THREE AND ONE HALF TIMES SAID WALL THICKNESS, AND A DEPTH RANGING FROM A MINIMUM OF ABOUT 0.010" TO A MAXIMUM WHICH IS ABOUT SAID WALL THICKNESS TO PERMIT FORMATION OF SAID SECOND SUBSTANTIALLY FLAT SECTIONS WHEN SAID LATERAL SPACING IS SAID MAXIMUM, BUT WHICH IS SUFFICIENTLY LESS THAN SAID WALL THICKNESS TO PERMIT FORMATION OF SAID SECOND SUBSTANTIALLY FLAT SECTIONS WHEN SAID LATERAL SPACING IS SAID MINIMUM, IN ORDER TO PROVIDE AS LARGE A NUMBER AND A CLOSE A SPACING AS POSSIBLE OF SAID GROOVES HAVING ADEQUATE DEPTH FOR HOLDING SAID SCREW POINT AGAINST SLIPPING AND FOR FACILITATING PROPER PIERCING OF SAID ONE PORTION BY HELPING TO MAINTAIN THE DESIRED PERPENDICULAR RELATIONSHIP BETWEEN THE AXIS OF SAID SCREW AND SAID ONE PORTION, WHILE MAINTAINING SAID VARYING CONTOUR, AND SAID ARCUATE SALIENTS HAVING ABOUT THE SAME DEPTH AS SAID GROOVES BUT A SUFFICIENTLY GREATER WIDTH TO MAINTAIN SAID SUBSTANTIALLY UNIFORM WALL THICKNESS OF SAID ONE PORTION, AND THEREBY RELIEVE CONCENTRATION OF STREES CAUSED BY FORMING SAID GROOVES.