1.

• X.)Bolted Connections (Steel)

A.) Introduction

1.) Types of bolts used withstructural steel

a.)A307- low carbon (lowest

strength) standard head size.

b.) A325- high strength - heavyduty nut.

2.

c.)A490 - high strength - heavy

duty nut.Sizes range from 1/2 to1-1/2 in 1/8 increments.

3.

2.)Types of Connections

a.) Tension/Compression Connection

(Axial Members - Trusses)

i.) Lap Joint - Bolts in single shear

- Eccentric - not as good

4.

ii.) Butt Joint - bolts inDouble Shear

- concentric

- better

5.

b.) Shear Connection (Beams)

-Simple Support (No momenttransferred at connection)

- Connect web only

- Bolts in Shear

+ + 6.

c.)Moment & Shear (Beam Connections)

- Fixed Support

- Connect Flange & Web

+ + d.)Any combination ofa.), b.), & c.) + + 7.

B.)Possible Way a Bolted Connectioncould fail (failure modes)

1.) Bolts fail in Shear

8.

2.) Member or Connection plates fail in

bearingor crushing

- making the bolt holes oblong

(crushingsteel in plate)

- excessive deformation

9.

3.)Member or Plates fail in tension

a.) failure by yielding on gross area is

b.) failure by fracture on net area

Gross Area Net Area a. b. 10.

4.)Member or Connecting plates fail byend or edge tear-out

enddistance too small or edgedistance too small 11.

C.) Design of Bolted Connections

- check all 4 possible failure modes:

1.) Bolt Shear

2.) Member/Plate bearing failure

3.) Member/Plate tension failure

4.) Member/Plate end or edge tear-out

12.

1.) Bolt Shear

P V = A B v,all Nn

N=__ P v ___(solving for N)

nA B v,all

P v = allowable load on connection,based on bolt shear (k)

A B = C.S.A. of one bolt (in 2 )

N =No. of bolts in connection

n= number of shear planes

13.

v,all = Allow. shear stress (ksi) ,Table 19-1

a.) Slip Critical -when no slippage of joint can be permitted.

b.) Bearing Type - when slippage of joint

joint can be permitted so that bolts can bear on connected parts.

c.) Threads in or out of shear plane (for bearing connections only)

14. threadsinshearplane threadsnotin shearplane 15. 2.) Member/Plate Bearing P P = dt p,all N P P = Allowable load on connectionbased on bearing(k) d = Bolt diameter (in.) t = thickness of member/plate (in.) N = Number of bolts in connection 16.

p,all= allowable bearing stress ofmember/plate (ksi)

= 1.5 t,ult

= 1.5 (58ksi) = 87 ksi for A36 steel

t,ultin Table 19-2 for othermaterials.

17.

3.) Tension in member/plates -must satisfy

two requirements:

P all< A g(0.60 Y )

P all< A n(0.50 t,ult )

A g= Gross CSA of member orconnection plate

Y = yield strength of member orplate

18.

A n= Net CSA of member or plate= A g- A holes

t,ult= ultimate strength of member orplate

19.

4.)Bolt Spacing Edge/End Distance

P L B L end L edge L edge L B 20.

a.)L end = distance from center ofstandard hole to end of connectedpart along the line of transmitted force.

Must satisfytworequirements:

L end> 2P B __

t,ult (t)

L end>Table J3.5

21.

P B = Applied load per bolt = P/N

t,ult = ultimate strength of member/plate

t = thickness of member or plate

22.

b.)L edge= distance from center of

standard hole to edge of connectedpart, perpendicular to line of force

L edge>TableJ3.5

23.

c.)L B= Distance between centerlines of

standard holes. Again,twocriteria

L B> 2.67 d(all directions)

L B> 2P B __ +d(in direction of load)

t,ult (t)2

d = bolt diameter

P B t,ult, & tdefined previously

24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34.

A.) INTRO. TO WELDED CONNECTIONS

1.) 6500 o F electric arc melts the weld electrode to the material being connected ( the base metal).

2.) Weld electrode must be compatible material for the base metal, i.e. same chemical makeup

35.

3.) E60xx means 60 ksi ultimate strength

would use with low carbon (A36 or 1020)

steel.

4.) Weld geometry

a.) Groove welds:

- Full Penetration

- Partial Penetration

b.) Fillet Welds

36.

B.) WELDED CONNECTION STRENGTH

1.) Groove Welds: Full strength of the connected part is developed if:

a.) full penetration

b.) full length

Edge prep. increases cost

37.

2.) Fillet Welds

Required size (a dimension) of weld is controlled by:

a.) Minimum size is controlled by thickness of the thicker of two parts joined. (Table 19-4)

b.) Maximum size is controlled by thethickness of the welded edge. (Table 19-4)

38.

2.) Fillet Welds

b.) Maximum size:

a max t 39.

2.) Fillet Welds

Required length of weld (L) is controlled by:

a.) weld shear strength:

P v= v,allt e (units of lb/in)

= (0.3 t,u) t e

t e= effective throat thickness

= a(sin45 o ) = 0.707a

P v=(0.3 t,u) (0.707a )

P v= 0.212 t,ua (units of lb/in of weld)

40.

b.) L>4a

c.) L>w

>width of part

d.) L>5 t min

e.) Returns>2a

return L = weld length Section View w t min a 41.