High-strength bolted connection structure with no fire protection

Abstract

The present invention provides a high-strength bolted connection structure for realizing a steel structure with no fire protection, which is capable of adequately assuring high-temperature strength of the connection in a high temperature region of 650° C., and which does not depend on a fire protection or protective structure using fire resistant material, wherein ultra-high-strength bolts having excellent fire resistance and excellent resistance to delayed fracture are used, which bolt have a tensile strength at room temperature (TS) of 1200 N/mm 2 or higher, and satisfies the relation that the shear proof stress at high temperature of 650° C. (bτt) is not less than (coefficient of slip at room temperature (μ)×design bolt tension (N 0 ))/(safety factor for long term load (ν)×cross-sectional area of bolt shank (bAs)).

1 . A high-strength bolted connection structure with no fire protection, the high-strength bolted connection structure having the fire resistance of a steel structure comprising columns and/or beams, characterized in that ultra-high-strength bolts having a bolt tensile strength (TS) at room temperature of 1200 N/mm 2  or higher and excellent fire resistance with a bolt shear proof stress (bτt) at 650° C. satisfying the relation <1> below, are used:  
         bτt≧μ×N   0 /(ν× bAs )   <1> 
       where 
 bτt: bolt shear proof stress at high temperature (N/mm 2 ) 
 bτt=TSt/{square root}3  
 
 TSt: tensile strength of the bolts at high temperature (N/mm 2 )  
 μ: coefficient of slip at room temperature  
 N 0 : design bolt tension (N)  
 ν: safety factor for long-term load  
 bAs: cross-sectional area of bolt shank (mm 2 ).  
 
     
     
         2 . A high-strength bolted connection structure with no fire protection according to  claim 1 , wherein, in said high-strength bolted connection structure, the long term allowable shear force (Qs) of said beam at room temperature satisfies the relation <2> below:  
         Qs≦{ns×bτ+ ( nf−ns )× bτt}×bAs    <2> 
       where 
 Qs: long term allowable shear force of the beam at room temperature (N) 
 Qs=fs×Ab  
 
 fs: long term allowable shear proof stress of the beam (N/mm 2 )  
 Ab: cross-sectional area (mm 2 )  
 ns: number of tension bolts in the floor slab on upper flange side of the beam  
 bτ: shear proof stress of bolt at room temperature (N/mm 2 ) 
 bτ=TS/{square root}3  
 
 TS: tensile strength of bolt at room temperature (N/mm 2 )  
 nf: number of tension bolts on the upper flange side of the beam  
 bτt: shear proof stress of bolt at high temperature (N/mm 2 ) 
 bτt=TSt/{square root}3  
 
 TSt: tensile strength of bolt at high temperature (N/mm 2 )  
 bAs: cross-sectional area of bolt shank (mm 2 ).  
 
     
     
         3 . A high-strength bolted connection structure with no fire protection according to  claim 1  or  2 , wherein said high-strength bolted connection structure is composed of sets of a high-strength bolt, a nut, and a washer, and joint metals, and wherein said nut and washer are a general structural hexagon nut and a structural high strength plain washer for which no fire resistance is provided.  
     
     
         4 . A high-strength bolted connection structure with no fire protection according to  claim 1  or  2 , wherein said high-strength bolted connection structure is composed of sets of high strength bolt, a nut, and a washer, and joint metals, and wherein a part or all of said joint metals are formed of steel material having an assured high-temperature strength.  
     
     
         5 . A high-strength bolted connection structure with no fire protection according to  claim 1  or  2 , wherein, in said high-strength bolted connection structure, a part or all of said columns and/or beams used are formed of steel material having an assured high temperature strength.  
     
     
         6 . A high-strength bolted connection structure with no fire protection according to  claim 1  or  2 , wherein said high-strength bolt is a ultra-high-strength bolt which contains, in % by weight, C: 0.30˜0.45%, Si: less than 0.10%, Mn: more than 0.40%˜less than 1.00%, P: less than 0.010%, S: 0.010% or less, Cr: 0.5% or more˜less than 1.5%, Mo: more than 0.35%˜less than 1.5%, V: more than 0.3%˜1.0% or less, with the balance being Fe and unavoidable impurities, and which has excellent fire resistance and resistance to delayed fracture such that following relations <3>, <4> are satisfied:  
         TS ≦(1.1× T+ 850)   <3> TS ≦(550× Ceq+ 1000)   <4> 
       where 
 TS: tensile strength of the high strength bolt at room temperature (N/mm 2 )  
 T: tempering temperature (° C.)  
 Ceq: carbon equivalent (%) 
 Ceq=C+(Mn/6)+(Si/24)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14).  
 
 
     
     
         7 . A high-strength bolted connection structure with no fire protection according to  claim 3 , wherein said high-strength bolt is an ultra-high-strength bolt which contains, in % by weight, C: 0.30˜0.45%, Si: less than 0.10%, Mn: more than 0.40%˜less than 1.00%, P: less than 0.010%, S: 0.010% or less, Cr: 0.5% or more˜less than 1.5%, Mo: more than 0.35%˜less than 1.5%, V: more than 0.3%˜1.0% or less, with the balance being Fe and unavoidable impurities, and which has excellent fire resistance and resistance to delayed fracture such that following relations <3>, <4> are satisfied:  
         TS ≦(1.1× T+ 850)   <3> TS ≦(550× Ceq+ 1000)   <4> 
       where 
 TS: tensile strength of the high strength bolt at room temperature (N/mm 2 )  
 T: tempering temperature (° C.)  
 Ceq: carbon equivalent (%) 
 Ceq=C+(Mn/6)+(Si/24)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14).  
 
 
     
     
         8 . A high-strength bolted connection structure with no fire protection according to  claim 4 , wherein said high-strength bolt is an ultra-high-strength bolt which contains, in % by weight, C: 0.30˜0.45%, Si: less than 0.10%, Mn: more than 0.40%˜less than 1.00%, P: less than 0.010%, S: 0.010% or less, Cr: 0.5% or more˜less than 1.5%, Mo: more than 0.35%˜less than 1.5%, V: more than 0.3%˜1.0% or less, with the balance being Fe and unavoidable impurities, and which has excellent fire resistance and resistance to delayed fracture such that following relations <3>, <4> are satisfied:  
         TS ≦(1.1× T+ 850)   <3> TS ≦(550× Ceq+ 1000)   <4> 
       where 
 TS: tensile strength of the high strength bolt at room temperature (N/mm 2 )  
 T: tempering temperature (° C.)  
 Ceq: carbon equivalent (%) 
 Ceq=C+(Mn/6)+(Si/24)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14).  
 
 
     
     
         9 . A high-strength bolted connection structure with no fire protection according to  claim 5 , wherein said high-strength bolt is an ultra-high-strength bolt which contains, in % by weight, C: 0.30˜0.45%, Si: less than 0.10%, Mn: more than 0.40%˜less than 1.00%, P: less than 0.010%, S: 0.010% or less, Cr: 0.5% or more˜less than 1.5%, Mo: more than 0.35%˜less than 1.5%, V: more than 0.3%˜1.0% or less, with the balance being Fe and unavoidable impurities, and which has excellent fire resistance and resistance to delayed fracture such that following relations <3>, <4> are satisfied:  
         TS ≦(1.1× T+ 850)   <3> TS ≦(550× Ceq+ 1000)   <4> 
       where 
 TS: tensile strength of the high strength bolt at room temperature (N/mm 2 )  
 T: tempering temperature (° C.)  
 Ceq: carbon equivalent (%) 
 Ceq=C+(Mn/6)+(Si/24)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14).