Optimal weight thin wall profile member and method of making same

Abstract

Thin-webbed profile member is intended for reacting primarily compressive load and have shape and cross-section dimensions constant along its length. The profile members have main strips and additional strips. The ratio of a width of an additional strip with common reinforcing ribs to a width of the main strip satisfying the expression: a/b=0.3-0.7 and the ratio of the thickness of the additional strip with common reinforcing ribs to the thickness of the main strip satisfying the expression: δ a /δ b =1.0 to 3.0 where: a is the width of the additional strip with common reinforcing ribs; b is the width of the main strip; δ a is the thickness of the additional strip with common reinforcing ribs; and δ b is the thickness of the main strip.

1 - 10 . (canceled) 
   
   
       11 . A method of determining the minimum area cross section of a thin-walled profile member capable of bearing a lengthwise compressive force applied to said member in a direction normal to the cross-section, said cross-sectional shape of said member being substantially constant along the length thereof, wherein said cross section comprises at least one of (1) at least two main strips and at least one additional strip having both ends connecting with respective ends of two of said main strips, said main strip having a thickness δ b  and a width b, said additional strip having a thickness δ 1  and a width a, and δ b /b being no larger than δ 1 /a, and (2) at least one main strip and at least one additional strip having one end connecting with an end of said main strip, said main strip having a thickness δ b  and a width b, said additional strip having a thickness δ c  and a width c, and δ b /b being no larger than δ c /c, and said cross section has a shape efficiency factor Σ=K f ×K m  where
     K   f =( i   2   /F   2 ) 2/5 ,       K   m   =[K   1/5 ]/[( b/δ   b ) 2/5 ],   i=inertia radius of said cross-sectional shape,   F=area of said cross-sectional shape, and   K=coefficient of local stability critical stress for said cross-sectional shape, the method comprising:   determining the values of the ratios a/b, δ a /δ b , c/b, and δ c /δ b  that maximize the value of Σ.   
   
   
       12 . The method of  claim 11 , wherein:
 said member has one of (1) a hollow, generally rectangular-shaped cross section, with the longer sides of said rectangle comprising said main strips and each shorter side of said rectangle comprising a said additional strip, and (2) a hollow, generally triangular-shaped cross section, with two sides of said triangle comprising said main strips and a third side of said triangle comprising said additional strip; and
     a/b= 0.3 to 0.7 and δ a /δ b =1.0 to 3.0. 
   
   
   
       13 . The method of  claim 11 , wherein:
 said member has one of (1) a generally I-shaped cross section, with the upright portion of said I comprising said main strip and each of four flanges forming the top and base of said I comprising a said additional strip, (2) a generally Z-shaped cross section, with the upright portion of said Z comprising said main strip, a flange at an angle to said main strip forming the top of said Z comprising one said additional strip, and a flange at an angle to said main strip forming the bottom of said Z comprising a second said additional strip, (3) a generally C-shaped cross section, with the upright portion of said C comprising said main strip, a flange forming the top of said C comprising one said additional strip, and a flange forming the bottom of said C comprising a second said additional strip, (4) a generally T-shaped cross-section, with the upright portion of said T comprising said main strip and each of two flanges forming the top of said T comprising a said additional strip, and (5) a generally L-shaped cross-section, with the upright portion of said L comprising said main strip and a flange forming the bottom of said L comprising a said additional strip; and
     c/b= 0.05 to 0.3 and δ c /δ b =1.0 to 3.0. 
   
   
   
       14 . The method of  claim 11 , wherein:
 said member has a generally U-shaped cross section with the sides of said U comprising said main strip, the bottom of said U comprising said additional strip, and flanges extending from the ends of the legs of said U comprising two said additional strips;
     a/b= 0.3 to 0.7 and δ a /δ b 1.0 to 3.0; and 
     c/b= 0.05 to 0.3 and δ c /δ b =1.0 to 3.0. 
   
   
   
       15 . A thin-walled profile member capable of bearing a lengthwise compressive force applied to said member in a direction normal to the cross-section thereof, said cross-sectional shape of said member being substantially constant along the length thereof and having the minimum area capable of bearing the compressive force, wherein:
 said cross section comprises at least one of (1) at least two main strips and at least one additional strip having ends connecting with respective ends of two of said main strips, said main strip having a thickness δ b  and a width b, said additional strip having a thickness δ a  and a width a, and δ b /b being no larger than δ a /a, and (2) at least one main strip and at least one additional strip having one end connecting with an end of said main strip, said main strip having a thickness δ b  and a width b, said additional strip having a thickness δ c  and a width c, and δ b /b being no larger than δ c /c;   said cross section has a shape efficiency factor Σ=K f ×K m , where
     K   f =( i   2   /F   2 ) 2/5 , 
     K   m    =[K/   1/5 ]/[( b/δ   b ) 2/5 ], 
   i=inertia radius of said cross-sectional shape,   F=area of said cross-sectional shape, and   K=coefficient of local stability critical stress for said cross-sectional shape; and   the values of the ratios a/b, δ a /δ b , c/b, and δ c /δ b  are chosen to maximize the value of Σ.   
   
   
       16 . The member of  claim 15 , wherein:
 said member has one of (1) a hollow, generally rectangular-shaped cross section, with the longer sides of said rectangle comprising said main strips and each shorter side of said rectangle comprising a said additional strip, and (2) a hollow, generally triangular-shaped cross section, with two sides of said triangle comprising said main strips and a third side of said triangle comprising said additional strip; and
     a/b= 0.3 to 0.7 and δ a /δ b =1.0 to 3.0. 
   
   
   
       17 . The member of  claim 15 , wherein:
 said member has one of (1) a generally I-shaped cross section, with the upright portion of said I comprising said main strip and each of four flanges forming the top and base of said I comprising a said additional strip, (2) a generally Z-shaped cross section, with the upright portion of said Z comprising said main strip, a flange at an angle to said main strip forming the top of said Z comprising one said additional strip, and a flange at an angle to said main strip forming the bottom of said Z comprising a second said additional strip, (3) a generally C-shaped cross section, with the upright portion of said C comprising said main strip, a flange forming the top of said C comprising one said additional strip, and a flange forming the bottom of said C comprising a second said additional strip, (4) a generally T-shaped cross-section, with the upright portion of said T comprising said main strip and each of two flanges forming the top of said T comprising a said additional strip, and (5) a generally L-shaped cross-section, with the upright portion of said L comprising said main strip and a flange forming the bottom of said L comprising a said additional strip; and
     c/b= 0.05 to 0.3 and δ c /δ b =1.0 to 3.0. 
   
   
   
       18 . The member of  claim 15 , wherein:
 said member has a generally U-shaped cross section with the sides of said U comprising said main strip, the bottom of said U comprising said additional strip, and flanges extending from the ends of the legs of said U comprising two said additional strips;
     a/b= 0.3 to 0.7 and δ a /δ b =1.0 to 3.0; and 
     c/b= 0.05 to 0.3 and δ c /δ b =1.0 to 3.0.