Self-centering damping column and damping brace

Abstract

A structural column includes a column body having a length Lc and a cross-section having a depth d that is greater than a width bc, with the column body having two end portions at ends of the length of the column body, a first end cap positioned at the first end portion of the column body where the first end cap has a first width greater than the width bc of the column body and has a first central line of the first width, and a second end cap positioned at the second end portion of the column body where the second end cap has a second width greater than the width bc of the column body and has a second central line of the second width. Additionally, the first central line and the second central line are off-center from a central line of the width of the column body.

What is claimed is: 
     
         1 . A structural column comprising:
 a column body having a length L c  and a cross-section, wherein the cross-section has a depth d that is greater than a width b c , the column body having two end portions at ends of the length of the column body;   a first end cap positioned at a first end portion of the two ends portions of the column body, the first end cap having a first width that is greater than the width b c  of the column body and having a first central line of the first width; and   a second end cap positioned at a second end portion of the two ends portions of the column body, the second end cap having a second width that is greater than the width b c  of the column body and having a second central line of the second width,   wherein the first central line of the first width and the second central line of the second width are off-center from a central line of the width of the column body.   
     
     
         2 . The structural column of  claim 1 , wherein the first end cap has a first cap portion having the first width b cp  and a second cap portion, wherein the second cap portion tapers from the first width b cp  to the width b c  of column body. 
     
     
         3 . The structural column of  claim 2 , wherein the second cap portion has a length of (b cp −b c )/2. 
     
     
         4 . The structural column of  claim 3 , wherein the first cap portion has a length of t cp , wherein the first end cap is positioned at the first end portion of the column body such that the first cap portion extends beyond an end of the column body by t cp /2. 
     
     
         5 . The structural column of  claim 4 , wherein the second end cap is identical to the first end cap. 
     
     
         6 . The structural column of  claim 1 , wherein the cross-section of the column body is rectangular, and wherein the column body, the first end cap, and the second end cap together exhibit self-centering and elastic buckling mode jump behavior characterized by a flag-shaped hysteresis loop that relates axial force to axial displacement. 
     
     
         7 . The structural column of  claim 6 , wherein the elastic buckling mode jump behavior and the flag-shaped hysteresis loop include:
 a pre-buckling linear phase;   a post-primary-buckling fixed-fixed mode stable phase;   a post-primary buckling fixed-fixed mode unstable phase;   a forward mode jump phase from fixed-fixed mode to pinned-pinned mode;   a post-secondary-buckling pinned-pinned mode phase; and   a backward mode jump phase from the pinned-pinned mode to the fixed-fixed mode.   
     
     
         8 . A structural brace comprising:
 a plurality of structural columns, wherein at least one structural column of the plurality of structural columns includes:
 a column body having a length L c  and a substantially rectangular cross-section, wherein the substantially rectangular cross-section has a depth d that is greater than a width b c  the column body having two end portions at ends of the length of the column body; 
 a first end cap positioned at a first end portion of the two ends portions of the column body, the first end cap having a first width that is greater than the width b c  of the column body and having a first central line of the first width; and 
 a second end cap positioned at a second end portion of the two ends portions of the column body, the second end cap having a second width that is greater than the width b c  of the column body and having a second central line of the second width, 
 wherein the first central line of the first width and the second central line of the second width are off-center from a central line of the width of the column body. 
   
     
     
         9 . The structural brace of  claim 8 , wherein the plurality of structural columns includes structural columns of different lengths. 
     
     
         10 . The structural brace of  claim 8 , further comprising an inner tube and an outer tube, wherein the inner tube and the outer tube are configured to place the at least one structural column into compression whenever the inner tube and the outer tube are translated relative to each other. 
     
     
         11 . The structural brace of  claim 10 , wherein:
 the inner tube includes a first inner tube end, a second inner tube end, and an inner tube interior space between the first inner tube end and the second inner tube end;   the outer tube includes a first outer tube end, a second outer tube end, and an outer tube interior space between the first outer tube end and the second outer tube end; and   the inner tube interior space and the outer tube interior space overlap in an overlapping space between the first inner tube end and the second outer tube end.   
     
     
         12 . The structural brace of  claim 11 , further comprising:
 a first plate and a second plate within the overlapping space; and   at least one pre-stressed strand coupling the first plate to the second plate,   wherein the at least one structural column is held between the first plate and the second plate by the at least one pre-stressed strand when the first plate and the second plate are in an unloaded state.   
     
     
         13 . The structural brace of  claim 12 , wherein the first plate and the second plate compress the at least one structural column when the overlapping space decreases by the first inner tube end and the second outer tube end moving closer to each other, and wherein the first plate and the second plate compress the at least one structural column when the overlapping space increases by the first inner tube end and the second outer tube end moving away from each other. 
     
     
         14 . The structural brace of  claim 13 , wherein when the overlapping space decreases, the first plate and the second plate compress the at least one structural column by the first inner tube end forcing the first plate toward the second plate and by the second outer tube end forcing the second plate toward the first plate. 
     
     
         15 . The structural brace of  claim 13 , wherein when the overlapping space increases, the first plate and the second plate compress the at least one structural column by:
 a first post in the outer tube interior space entering the overlapping space through the first inner tube end and forcing the first plate toward the second plate, and   a second post in the inner tube interior space entering the overlapping space through the second outer tube end and forcing the second plate toward the first plate.   
     
     
         16 . The structural brace of  claim 12 , further comprising:
 a third plate positioned between the first plate and the second plate,   wherein at least one structural column of the plurality of structural columns is coupled to the first plate and to the third plate and is not coupled to the second plate.   
     
     
         17 . The structural brace of  claim 16 , further comprising:
 a fourth plate positioned between the first plate and the third plate,   wherein at least one structural column of the plurality of structural columns is coupled to the first plate and to the fourth plate and is not coupled to the second plate or the third plate.   
     
     
         18 . A method of providing a structural column exhibiting an elastic buckling mode jump behavior characterized by a target flag-shaped hysteresis loop that relates axial displacement of the structural column to axial force exerted on the structural column, the method comprising:
 accessing dimensional parameters for the structural column,
 wherein the structural column includes:
 a column body having a length L c  and a cross-section, wherein the cross-section has a depth d that is greater than a width b c , the column body having two end portions at ends of the length of the column body, and having a first central line A c  of the width b c , and 
 two end caps positioned at the end portions of the column body, each end cap including an end cap portion having: a width b cp  that is greater than the width b c  of the column body, a length t cp , and a second central line A cp  of the width b cp , and 
 
 wherein the dimensional parameters include at least two of:
 the length L c  of the structural column, 
 the width b c  of the structural column, 
 the depth b c  of the structural column, 
 the length t cp  of the end cap portion, 
 the width b cp  of the end cap portion, 
 a length L t  between ends of the two end caps; or 
 a distance e 0  between the first central line A c  and the second central line A cp ; 
 
   accessing at least one structural column requirement from at least one of a target peak axial force of the hysteresis loop, a target energy dissipation per hysteresis loop cycle, or a target elastic behavior of column materials to achieve self-centering behavior; and   adjusting at least one of the dimensional parameters based on the at least one structural column requirement.   
     
     
         19 . The method of  claim 18 , wherein adjusting at least one of the dimensional parameters includes adjusting at least one of the following metrics to achieve the at least one structural column requirement:
 a slenderness defined as L c /b c ,   a cap thickness ratio defined as t cp /L t ,   a cap width ratio defined as b cp /b c ,   an initial eccentricity ratio defined as e 0 /L t ,   a depth ratio defined as d/b c , and   the length L t .