钢结构英文课件.ppt

,3.8 Design of HS bolted connection,Detailling requirements(构造要求)Classification Bolt installation Friction coefficientStrength requirement（受力要求）Load transfer mechanism Strength,1.A connection with high-strength bolts is classified as either a bearing or slip-critical connection.Bearing Slippage acceptableShear and bearing on the connectorSlip-critical Slippage unacceptable(Proper installation)Sufficient shear and bearing strength in overload that causes slip.Used in the important connection,3.8.1 Detailing of HS bolted connection,1)Tightening methods A.Turn of the Nut(扭角法)B.Calibrated wrench tightening(扭矩法)C.Twist-off-type tension-control bolt（拧断型拉力控制螺栓）D.Direct tension indicator(拉力测量仪),2.Bolt installation,A.Turn of the Nut,B.Calibrated wrench tightening,C.Twist-off-type tension-control bolt,D.Direct tension indicator,The following factors are considered as Reduction of material properties(0.9)Reduction of over tensioning of bolt(0.9)Reduction of shear which will decrease tension strength of bolt(1.2)safety factor 0.9 Bolt preload is,Aebolt effective area；fubolt tension strength,fu=830N/mm2 for grade 8.8 and fu=1040N/mm2 for grade 10.9,2）Preload design,Friction coefficient depends on the surface treatment and the steel grade.Table 7.2 for china,3）Friction coefficient,(1)Behavior of HS bolt,3.8.2 Strength of HS bolted connection,where:0.9reciprocal of resistance factor R(R=1.111)；nfnumber of friction surface；-friction coefficientPdesign value of preload,（2）Shear capacity of single bolt,For the slip-critical bolt,N,O,HS,Ordinary,Strength is,Shear capacity is,Bearing capacity is,For the bearing type bolt,where:Ae-Effective area of bolt；de-Effective diameter of bolt；ftbdesign value of bolt tension strength The results is approximately equal,（3）Tension capacity of single bolt,For the slip-critical bolt,For the bearing type bolt,（4）Combined tension and shear,For the slip-critical bolt,Design value of tension and shear load of single boltDesign value of tension and shear capacity of single bolt,For the bearing type bolt,And to avoid bearing failure,should also satisfy as,1.2 is reduction of bearing capacity due to the tension of bolt,1)Axial tension The required bolts is(based on uniform distribution),For the bearing type bolt,For the slip-critical bolt,2 Shear capacity of bolt group,Calculation is similar as before：,Shear componet is,2）Combined torsion and shear,The strength of 1#bolt is checked as,Torsion componet is,2）Moment,3 Tension capacity of bolt group,1)Axial tension The required bolts is(based on uniform distribution),The design requirement is,The firm comtact is assumed as,3)Eccentric loading,The firm comtact is assumed and both types are designed by substituting method as:,Conclusion,For the slip-critical bolt group,For the bearing type bolt group,Shear of single bolt is,Tension of single bolt is,（4）Combined tension and shear,（4）Combined tension,shear and moment,For the slip-critical bolt group,Shear of single bolt is,Where,For the single slip-critical bolt,The strength of bolt is,Shear of single bolt is,Max.tension of single bolt is,For the bearing type bolt group,Design a lap joint shown in the figure.steel isQ235Band High strength bolt is M20 with grade 8.8,faying surface is sand-blast(喷砂)and the design value of axial load N=800kN.,Example 1,（1）Slip-critical connection,The preload of bolt is checked as,The friction coefficient is,Shear capacity of single bolt is,The required number is,select 9,（2）bearing type connection,It is checked as,Capacity of single bolt is,The required number is,select 6,