_analysis of Moment Resisting Connections
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Transcript of _analysis of Moment Resisting Connections
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analysis of moment resisting connections
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basic principles of connection designProvide as direct a load path as possibleAvoid complex stress conditionsWeld in the shop, bolt on site
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Welded connections
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moment connection of an I-BeamBending moment is carried mainly by the flangesTherefore connect flanges for moment transfer
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moment connection of an I-BeamWelded connectionFillet weldsFull penetration weldsCompression transfer can also be accomplished through direct bearing
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shear connection of an I-BeamShear is carried mainly by the webTherefore connect the web for shear transfer
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shear connection of an I-BeamFillet welds in shear are commonly usedConnect entire web and adjust weld size to suit shear load
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moment connection of a plateStress in weld = M (d/2) / I= M (d/2) / (ad3/12) [kN/m2]q= a= M (d/2) / (d3/12)= M (d/2) / I [kN/m]WhereI= I/a
Then choose a weld size a that will carry q
q = .a where a = weld sized
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moment connection of a plateCan also use simplified approach:
Break moment into a force coupleChoose a suitable weld sizeThen calculate the required length of the weld to carry the tension force T
q = T/l where l = weld lengthdResultant tension force T = M/dC = T
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welded shear plate
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simplified approachBreak eccentric load up into a vertical force along the vertical weld and a pair (couple) of horizontal forces along the horizontal weldsThen choose lengths of welds to carry the calculated forcesVV.e/dV.e/dVde
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Stress calculations+
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Stress calculations for vertical force VDivide shear equally amongst all the weld lines
q = V / (total length of weld)
Choose a weld size that can carry the stress q
Note q is actually a force per length [kN/m]qV
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Stress calculations for Moment M = V.eTreat the weld group as a cross-section subjected to a torsional moment
Ip2 = Ix2 + Iy2where I = I/a
qAx = M yA / IpqAy = M xA / Ip
qAM = (qAx2 + qAy2)0.5
Similarly for point BThen select weld size for max. q
qAx qAy qBx qBy yAxBxAyBA B qAM qBM
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Stress calculations for combined V and MVM = V.eqAx qAy qAV qA Combine the weld stress components from the vertical force and the torsional moment
qA = [qAx2 + (qAV + qAy)2]0.5
Similarly for point B or any other point that might be critical
Then select weld size for the maximum value of q
A B
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example of a complex connectionColumn tree for Times Square 4, NYC
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bolted connections
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moment splice in a column
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moment splice of an I-BeamBolted connectionDivide tension and compression resultant equally between bolts
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shear connection in bridge diaphragm girder
(Alex Fraser Bridge)
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shear connection of an I-BeamBolted connections to transfer shear are commonly usedConnect entire web to avoid stress concentrations and shear lag
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shear connection via end plateCoped flanges to fit in between column flangesEnd plate
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moment connection with and end or base plate
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moment connection with fully welded end plateMhihmaxTiTmaxTi = Tmax (hi / hmax)
M = Ti hiC = Ti
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pre-tensioned moment connection
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pre-tensioned Moment ConnectionApply both tension and compression forces to pre-tensioned bolts. Compression force can be seen as a release of the tension force.M=
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bolted shear plate
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vertical loadPVPVPDivide the force by n, the number of bolts
VP = P / n
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moment M FxMFyMFMiyixiTreat the bolt group as a cross-section subjected to a torsional moment
Ip = i A ri2 = i A (xi2 + yi2)
and with IP = IP/A
FxM = M yi / IpFyM = M xi / Ip
FMi = (FxM2 + FyM2)0.5
Then select a bolt size for the maximum force FM
ribolt area Abolt i
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combined vertical force and momentFxMFyMVPFmax
Fmax = [FxM2 + (FyM + VP)2]0.5
Then select a bolt size for the maximum force Fmax