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1、3.8 Design of HS bolted connection1.Detailling requirements (构造要求构造要求)v Classificationv Bolt installation v Friction coefficient2.Strength requirement （受力要求）（受力要求）v Load transfer mechanismv Strength 1.A connection with high-strength bolts is classified as either a bearing or slip-critical connection
2、.vBearing uSlippage acceptableuShear and bearing on the connectorvSlip-critical uSlippage unacceptable (Proper installation)uSufficient shear and bearing strength in overload that causes slip. uUsed in the important connection3.8.1 Detailing of HS bolted connection1) Tightening methods A. Turn of th
3、e Nut (扭扭角角法法) B. Calibrated wrench tightening (扭扭矩矩法法) C. Twist-off-type tension-control bolt （拧断型（拧断型拉力拉力控制螺栓）控制螺栓） D. Direct tension indicator (拉力拉力测量测量仪仪)2. Bolt installationA. Turn of the Nut B. Calibrated wrench tightening C. Twist-off-type tension-control bolt D. Direct tension indicator The
4、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 isuefAP2 . 19 . 09 . 09 . 0Aebolt effective area ；fubolt tension strength,fu =830N/m
5、m2 for grade 8.8 and fu =1040N/mm2 for grade 10.92） Preload designGrade Nominal diameterM16M20M22M24M27M308.88012515017523028010.9100155190225290355FFriction coefficient depends on the surface treatment and the steel grade. Table 7.2 for china3） Friction coefficient(1) Behavior of HS bolt HSNO123412
6、34ordinaryabNN/2N/23.8.2 Strength of HS bolted connectionNO12341234HSOrdinaryabNN/2N/2PnNfbv9 . 0where: 0.9reciprocal of resistance factor R (R=1.111)；nfnumber of friction surface；-friction coefficientPdesign value of preload（2）Shear capacity of single boltFor the slip-critical bolt,NO12341234HSOrdi
7、narybvevbvfdnN42bcbcf tdNbcbvbNNN?minminStrength isShear capacity isBearing capacity isFor the bearing type bolt,PNbt8 .0btebtebtfdfAN42where: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 si
8、ngle boltFor the slip-critical bolt,For the bearing type bolt,1bvvbttNNNNbvbtvtNNNN、（4）Combined tension and shearFor the slip-critical bolt,Design value of tension and shear load of single boltDesign value of tension and shear capacity of single boltFor the bearing type bolt,122bttbvvNNNNAnd to avoi
9、d bearing failure, should also satisfy as2 . 1bcvNN 1.2 is reduction of bearing capacity due to the tension of bolt1) Axial tension The required bolts is (based on uniform distribution)bvNNn bNNnmin NNFor the bearing type bolt,For the slip-critical bolt,2 Shear capacity of bolt group Calculation is
10、similar as before： FTTxyN1TN1TxN1Tyr11F1N1FShear componet isnFNF 12）Combined torsion and shearniniiininiiiTyniniiininiiiTxyxxTrxyxrTNyxyTryyxrTN11221111122111122111112211bvFTyTxNNNN21121?The strength of 1# bolt is checked asbFTyTxNNNNmin21121?Torsion componet isbtNNn N2）MomentM3 Tension capacity of
11、bolt group 1) Axial tension The required bolts is (based on uniform distribution)MM1 2 3 4y1y2N1N2N3N4Compre.NAnnyNyNyNML2211nnyNyNyNyNL332211niiyyMN1211The design requirement isbtNN 1The firm comtact is assumed as 3) Eccentric loading The firm comtact is assumed and both types are designed by subst
12、ituting method as:btniiMNyyMnNNnNN12111Ne1 2 3 4M=NeNy1y2N1N2N3N4N.A.MN1 bvvbttNNNN122 bttbvvNNNN2 . 1bcvNN ConclusionFor the slip-critical bolt group,For the bearing type bolt group,Shear of single bolt isNVnVNv Tension of single bolt isnNNt 1 2 3 4NVNV（4）Combined tension and shearMNVPNyyMnNNbtniit
13、8 .01211 1 2 3 4M=NeNy1y2N1N2N3N4NAMNVV（4）Combined tension, shear and momentFor the slip-critical bolt group,nVNNvv 1 Shear of single bolt is 111 bvvbttNNNNPnNfbv 9 .0PNbt8.0 WhereFor the single slip-critical bolt ,The strength of bolt is nVNv 1 Shear of single bolt is Max.tension of single bolt is
14、niityyMnNN121112121 bttbvvNNNN2 .1and1bcvNNFor the bearing type bolt group,MNV1 2 3 4M=NeNy1y2N1N2N3N4N.A.MNVVDesign 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 1kNP125
15、45. 0kNPnNfbv3 .10112545. 029 . 09 . 09 .73 .101800bvNNn2/250mmNfbv2/470mmNfbc （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 connectionIt is checked as Capacity of single bolt is The required number iskNfdnNbvvbv15725042014. 324221 . 5157800minNNnkNftdNbcbc1884702020select 61.Problem 12、习题、习题3.6 (M20,Q235 change to Q345, sand-blast faying surface)3、习题、习题3.8(120 change to 130)Assignment
