Ductile Fuse for Special Concentrically Braced Frames and Related Methods

Abstract

Embodiments of the present disclosure provide a structural improvement in braced frame structures. An exemplary solution involves heat-treating a mid-section region of a steel brace, the steel brace comprising hollow structural sections tubing; after heat-treating the mid-section region, cooling the mid-section region of the steel brace; wherein the heat-treated steel brace has changed mechanical properties due to the heat-treatment, the changed mechanical properties including improved material ductility, work hardening ability, and notch toughness; and coupling the heat-treated steel brace to a gusset plate within a braced building frame structure without need of gusset plate reinforcement.

1 . A method comprising:
 heat-treating a mid-section region of a steel brace, the steel brace comprising hollow structural sections tubing;   after heat-treating the mid-section region, cooling the mid-section region of the steel brace causing the heat-treated steel brace to change mechanical properties due to the heat-treatment, the changed mechanical properties including improved material ductility, work hardening ability, and notch toughness; and   coupling the heat-treated steel brace to a gusset plate within a braced building frame structure without need of gusset plate reinforcement.   
     
     
         2 . The method of  claim 1 , further comprising coupling the gusset plate to a column or brace within the braced building frame structure. 
     
     
         3 . The method of  claim 1 , wherein the steel brace comprises cold rolled steel. 
     
     
         4 . The method of  claim 5 , wherein the steel brace is heat-treated at a temperature that relieves residual stresses from prior cold work on the steel brace. 
     
     
         5 . The method of  claim 1 , wherein the mid-section region is heat-treated at a temperature of at least 700° C. 
     
     
         6 . The method of  claim 1 , wherein the mid-section region is heat-treated at a temperature of 700° C. for 30 minutes. 
     
     
         7 . The method of  claim 6 , wherein the mid-section region is cooled at 6° C./min before removing the steel brace from a furnace used in heat-treating the steel brace. 
     
     
         8 . The method of  claim 7 , wherein the mid-section is cooled to 550° C. before removing the steel brace from the furnace used in heat-treating the steel brace. 
     
     
         9 . The method of  claim 8 , wherein the heating and cooling treatments are completed within 2 hours. 
     
     
         10 . The method of  claim 1 , wherein the mid-section region is heat-treated at a temperature of 700° C. for 30 minutes. 
     
     
         11 . The method of  claim 10 , wherein the mid-section region is cooled at 0.6° C./min before removing the steel brace from a furnace used in heat-treating the steel brace 
     
     
         12 . The method of  claim 11 , wherein the mid-section is cooled to 550° C. before removing the steel brace from the furnace used in heat-treating the steel brace. 
     
     
         13 . The method of  claim 1 , further comprising cutting the steel brace to a final length, wherein the heat treatment of the steel brace is performed before the steel brace is cut to the final length. 
     
     
         14 . The method of  claim 1 , further comprising cutting a hole or slot in the steel brace, wherein the heat-treatment of the steel brace is performed before the hole or slot is cut into the steel brace. 
     
     
         15 . The method of  claim 1 , wherein an end of the mid-section region of the brace is at one brace depth away from an edge of the gusset plate. 
     
     
         16 . A braced frame structure comprising:
 a heat-treated steel brace having a mid-section region of the steel brace with changed mechanical properties as compared to outer regions of the steel brace, the changed mechanical properties including improved material ductility, work hardening ability, and notch toughness; and   a gusset plate coupled to the heat-treated steel brace without need of gusset plate reinforcement.   
     
     
         17 . The braced frame structure of  claim 16 , further comprising a column or brace coupled to the gusset plate. 
     
     
         18 . The braced frame structure of  claim 16 , wherein the steel brace comprises cold rolled steel. 
     
     
         19 . The braced frame structure of  claim 16 , wherein the mid-section of the steel brace is relieved of residual stresses from prior cold work on the steel brace. 
     
     
         20 . The braced frame structure of  claim 16 , wherein an end of the mid-section region of the brace is at one brace depth away from an edge of the gusset plate.