Buckling restrained braces and damping steel structures

Abstract

The present invention relates to a buckling restrained brace capable of absorbing vibration energy produced by an earthquake, wind power and the like, in a building and a steel structure. The buckling restrained brace of the present invention is accomplished by a buckling restrained brace 1 wherein a steel-made center axial member 3 is passed through a buckling-constraining concrete member 2 reinforced with a steel member 6 , and an adhesion-preventive film 4 is provided to the interface between the steel-made center axial member and buckling-constraining concrete 5 , the adhesion-preventive film showing a secant modulus in the thickness direction of at least 0.1 N/mm 2 between a point which shows a compressive strain of 0% and a point which shows a compressive strain of 50%, and up to 21,000 N/mm 2 between a point which shows a compressive strain of 50% and a point which shows a compressive strain of 75%, and having a thickness d t in the plate thickness direction of the steel-made center axial member and a thickness d w in the plate width direction thereof from at least 0.5 to 10% of the plate thickness t and from at least 0.5 to 10% of the plate width w, respectively, and by the application of the buckling restrained brace to a damping steel structure.

1 . A buckling restrained brace ( 1 ) wherein a steel-made center axial member ( 3 ) is passed through a buckling-constraining concrete member ( 2 ) reinforced with a steel member ( 6 ), and an adhesion-preventive film ( 4 ) is provided to the interface between the steel-made center axial member ( 3 ) and buckling-constraining concrete ( 5 ), 
 the adhesion-preventive film ( 4 ) showing a secant modulus in the thickness direction of at least 0.1 N/mm 2  between a point which shows a compressive strain of 0% and a point which shows a compressive strain of 50%, and up to 21,000 N/mm 2  between a point which shows a compressive strain of 50% and a point which shows a compressive strain of 75%, and having a thickness (d t ) in the plate thickness direction of the steel-made center axial member ( 3 ) and a thickness (d w ) in the plate width direction thereof from at least 0.5 to 10% of the plate thickness (t) and from at least 0.5 to 10% of the plate width (w), respectively.    
   
   
       2 . A buckling restrained brace according to  claim 1 , wherein the steel-made center axial member ( 3 ) is a steel material showing a 0.2% proof stress or a yield point stress of up to 130 N/mm 2 .  
   
   
       3 . A buckling restrained brace according to  claim 1 , wherein the steel-made center axial member ( 3 ) is a steel material showing a 0.2% proof stress or a yield point stress of 130 to 245 N/mm 2 .  
   
   
       4 . A buckling restrained brace according to  claim 1 , wherein the steel-made center axial member ( 3 ) has a minimum cross-sectional area in a central portion ( 21 ) in the longitudinal direction having a restricted length ratio which is the ratio of the length of the central portion ( 21 ) to the whole length, and the steel-made center axial member has a cross-sectional area larger than the minimum cross-sectional area of the central portion ( 21 ) in the longitudinal direction, at both ends ( 22 ,  23 ) in the longitudinal direction connectively provided to the central portion ( 21 ) in the longitudinal direction.  
   
   
       5 . A buckling restrained brace according to  claim 4 , wherein the steel-made center axial member ( 3 ) shows an axial equivalent stiffness of at least 1.5 times that of the steel-made center axial member ( 3 ) in any one of  claims 1  to  3  which have same-sectional area from one end to the other end, passing through the central portion ( 21 ) in the length direction of said member ( 3 ).  
   
   
       6 . A buckling restrained brace according to  claim 1 , wherein each of the cross-sectional areas ( 22 - 1 ,  23 - 1 ) at both ends ( 22 ,  23 ) in the longitudinal direction of the steel-made center axial member ( 3 ) which is obtained by subtracting a through hole-formed deficient area of the corresponding through holes ( 26 ) for bolt insertion passing is at least 1.2 times the cross-sectional area ( 21 - 1 ) of the central portion ( 21 ) in the longitudinal direction of the steel-made center axial member ( 3 ).  
   
   
       7 . A buckling restrained brace according to  claim 1 , wherein the steel member ( 6 ) is a reinforcing bar ( 6 - 1 ).  
   
   
       8 . A buckling restrained brace according to  claim 1 , wherein a lid ( 24 ) is fixed to at least one end of the buckling-constraining concrete member ( 2 ).  
   
   
       9 . A buckling restrained brace according to  claim 1 , wherein a slip stopper ( 25 ) is provided to the center of the steel-made center axial member ( 3 ).  
   
   
       10 . A buckling restrained brace according to  claim 1 , wherein the buckling restrained brace ( 1 ) having the steel-made center axial member ( 3 ) which is provided with through holes (  26 ) for bolt insertion passing at both ends ( 22 ,  23 ), and steel-made connecting plates ( 27 ) are friction jointed with high tension bolts by clamping, while the friction face sides at both ends ( 22 ,  23 ) of the steel-made center axial member ( 3 ) which are contacted with the respective friction face sides of the steel-made connecting plates ( 27 ) or the friction face sides of the steel-made connecting plates ( 27 ) which are contacted with the respective friction face sides at both ends ( 22 ,  23 ) of the steel-made center axial member are made to have a higher surface hardness and a higher surface roughness than the counterpart friction face sides.  
   
   
       11 . A buckling restrained brace according to  claim 1 , wherein at least one set comprising three layers which are formed from a C-shaped cross-sectional inside steel plate ( 29 ), a visco-elastic sheet ( 30 ) and a C-shaped cross-sectional outside steel plate ( 31 ) is fastened to each of the sides of the buckling-constraining concrete member ( 2 ) of the buckling restrained brace ( 1 ), 
 one end ( 32 ) of the C-shaped cross-sectional inside steel plate ( 29 ) is fastened to one end ( 34 ) of the buckling restrained brace ( 1 ), and    the other end ( 33 ) of the C-shaped cross-sectional outside steel plate ( 31 ) is fastened to the other end ( 35 ) of the buckling restrained brace ( 1 ) in the direction opposite to the one end ( 32 ) of the C-shaped cross-sectional outside steel plate ( 29 ).    
   
   
       12 . A damping steel structure ( 38 ) wherein the buckling restrained braces ( 1 ) according to  claim 1  or  4  are placed in the damping steel structure ( 38 ) which is formed with columns ( 36 ) and beams ( 37 ) prepared from a steel material showing a yield point stress higher than that of the steel-made center axial members ( 3 ) of the buckling restrained braces ( 1 ), 
 the buckling restrained braces ( 1 ) showing both elastic and plastic behavior when the damping steel structure ( 38 ) vibrates under vibration action, and    the damping steel structure ( 38 ) which is formed with the columns and the beams, showing elastic behavior.